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K Number
DEN180032
Device Name
Synovasure Alpha Defensin Lateral Flow Test Kit, Synovasure Alpha Defensin Lateral Flow Test Kit (5 Test), Synovasure Alpha Defensin Lateral Flow Test Kit (10 Test), Synovasure Alpha Defensin Lateral Flow Test Kit (30 Test), Synovasure Alpha Defensin Control Kit
Manufacturer
CD Diagnostics Inc.
Date Cleared
2019-05-23

(328 days)

Product Code
QGN
Regulation Number
866.3230
AI/MLSaMDIVD (In Vitro Diagnostic)TherapeuticDiagnosticis PCCP AuthorizedThirdparty
Intended Use
The Synovasure Alpha Defensin Lateral Flow Test Kit is a qualitative visually read immunochromatographic assay for the detection of human host response proteins, Alpha Defensins 1-3, in the synovial fluid of adults with a total joint replacement who are being evaluated for revision surgery. The Synovasure Alpha Defensin Lateral Flow Test Kit results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of periprosthetic joint infection (PJI). The Synovasure Alpha Defensin Lateral Flow Test Kit is not intended to identify the etiology or severity of a PJI. The Synovasure Alpha Defensin Control Kit is used in the Synovasure Alpha Defensin Lateral Flow Test Kit as assayed quality control samples to monitor performance and reliability of the Synovasure Alpha Defensin Lateral Flow Test Kit.
Device Description
The Synovasure Alpha Defensin Lateral Flow Test Kit (Synovasure LFT) is an immunoassay for the detection of alpha defensin levels in the synovial fluid of patients with a potential PJI. Antibodies specific to alpha defensin bind host alpha defensin in the synovial fluid, become immobilized on the lateral flow test strip, and are detected as a colored line due to the use of a colloidal gold reporter. Synovasure Alpha Defensin Lateral Flow Test Kit contains two sub components: - 1. Synovasure Alpha Defensin Lateral Flow Test Device - 2. Synovasure Lateral Flow Sample Prep Assembly The Synovasure Lateral Flow Sample Prep Assembly further contains - 1. One Synovasure Dilution Buffer Bottle - 2. One Sample Cup - 3. Two Microsafe Tubes The Synovasure Alpha Defensin Lateral Flow Test Device is a cassette that includes a reagent strip. Each cassette contains a reagent strip with all the critical components for the assay. The Synovasure Alpha Defensin Lateral Flow Test Kit is accompanied by the Synovasure Alpha Defensin Control Kit. The Synovasure Alpha Defensin Control Kit further contains - 1. Synovasure Alpha Defensin Positive Control - 2. Synovasure Alpha Defensin Negative Control - 3. Synovasure Control Reconstitution Bottle The positive control contains 0.25 mL of 16 µg/mL alpha defensin in synthetic synovial fluid and the negative control contains 0.25 mL of synthetic synovial fluid. Additional materials required but not provided include 1. Timer
More Information

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No
The device is a visually read immunochromatographic assay, which is a traditional laboratory test method and does not involve AI or ML for interpretation or analysis.

No.
The device is an in vitro diagnostic (IVD) test kit intended to aid in the diagnosis of periprosthetic joint infection (PJI) by detecting specific proteins in synovial fluid. It does not provide therapy or treatment.

Yes
The intended use states that the device results are "intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of periprosthetic joint infection (PJI)." This clearly indicates its role as a diagnostic aid.

No

The device is a lateral flow immunoassay kit, which is a physical diagnostic test kit containing reagents, test strips, and sample preparation components. It is not software.

Yes, this device is an IVD (In Vitro Diagnostic).

Here's why:

  • Intended Use: The intended use explicitly states that the device is a "qualitative visually read immunochromatographic assay for the detection of human host response proteins, Alpha Defensins 1-3, in the synovial fluid... as an aid in the diagnosis of periprosthetic joint infection (PJI)." This clearly indicates that the device is used to perform a test on a biological sample (synovial fluid) to provide information for diagnostic purposes.
  • Device Description: The description details an "immunoassay for the detection of alpha defensin levels in the synovial fluid." This further confirms that the device is designed to analyze a biological sample.
  • Sample Type: The device is intended for use with "synovial fluid," which is a biological specimen.
  • Diagnostic Aid: The results are intended to be used "as an aid in the diagnosis of periprosthetic joint infection (PJI)." This is a key characteristic of an IVD.

The device fits the definition of an In Vitro Diagnostic device, which is a medical device intended to be used in vitro for the examination of specimens derived from the human body solely or principally for the purpose of providing information concerning a physiological or pathological state, or a congenital abnormality, or to determine the compatibility of tissues and organs, or to monitor therapeutic measures.

N/A

Intended Use / Indications for Use

The Synovasure Alpha Defensin Lateral Flow Test Kit is a qualitative visually read immunochromatographic assay for the detection of human host response proteins, Alpha Defensins 1-3, in the synovial fluid of adults with a total joint replacement who are being evaluated for revision surgery. The Synovasure Alpha Defensin Lateral Flow Test Kit results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of periprosthetic joint infection (PJI). The Synovasure Alpha Defensin Lateral Flow Test Kit is not intended to identify the etiology or severity of a PJI.

The Synovasure Alpha Defensin Control Kit is used in the Synovasure Alpha Defensin Lateral Flow Test Kit as assayed quality control samples to monitor performance and reliability of the Synovasure Alpha Defensin Lateral Flow Test Kit.

Product codes (comma separated list FDA assigned to the subject device)

QGN

Device Description

The Synovasure Alpha Defensin Lateral Flow Test Kit (Synovasure LFT) is an immunoassay for the detection of alpha defensin levels in the synovial fluid of patients with a potential PJI. Antibodies specific to alpha defensin bind host alpha defensin in the synovial fluid, become immobilized on the lateral flow test strip, and are detected as a colored line due to the use of a colloidal gold reporter.
Synovasure Alpha Defensin Lateral Flow Test Kit contains two sub components:

  1. Synovasure Alpha Defensin Lateral Flow Test Device
  2. Synovasure Lateral Flow Sample Prep Assembly
    The Synovasure Lateral Flow Sample Prep Assembly further contains
  3. One Synovasure Dilution Buffer Bottle
  4. One Sample Cup
  5. Two Microsafe Tubes
    The Synovasure Alpha Defensin Lateral Flow Test Device is a cassette that includes a reagent strip. Each cassette contains a reagent strip with all the critical components for the assay.
    The Synovasure Alpha Defensin Lateral Flow Test Kit is accompanied by the Synovasure Alpha Defensin Control Kit. The Synovasure Alpha Defensin Control Kit further contains
  6. Synovasure Alpha Defensin Positive Control
  7. Synovasure Alpha Defensin Negative Control
  8. Synovasure Control Reconstitution Bottle
    The positive control contains 0.25 mL of 16 µg/mL alpha defensin in synthetic synovial fluid and the negative control contains 0.25 mL of synthetic synovial fluid.
    Additional materials required but not provided include
  9. Timer

Mentions image processing

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Mentions AI, DNN, or ML

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Input Imaging Modality

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Anatomical Site

synovial fluid of adults with a total joint replacement (knee and/or hip arthroplasty)

Indicated Patient Age Range

adults (subject was >22 years of age)

Intended User / Care Setting

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Description of the training set, sample size, data source, and annotation protocol

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Description of the test set, sample size, data source, and annotation protocol

Prospective Study:
Sample Size: 305 prospective synovial fluid samples.
Data Source: Clinical samples collected from 3 US medical centers with high volumes of revision surgery.
Annotation Protocol: Reference method utilized the Musculoskeletal Infection Society (MSIS) criteria. Patients are diagnosed with PJI if they meet one major criterion or any 3 of the 5 minor criteria. Final status determination was adjudicated by a two-physician panel, with discrepant opinions being resolved by consultation of a third physician.

Retrospective Remnant Clinical Samples:
Sample Size: 65 MSIS positive retrospective samples evaluated, interspersed with sufficient negative specimens to maintain relative disease prevalence consistent with what was observed in the prospective study population.
Data Source: Fresh retrospective synovial fluid collections. Residual samples were anonymized and assigned new case ID numbers.
Annotation Protocol: Synovasure LFT results were compared to a status determination based on positive confirmation of three minor MSIS criteria (neutrophil %, positive culture, and WBC count).

Summary of Performance Studies (study type, sample size, AUC, MRMC, standalone performance, key results)

Prospective Clinical Study:
Study Type: Clinical Sensitivity and Specificity
Sample Size: 305 prospective synovial fluid samples. After adjudication, 57 prospective samples were identified as positive by MSIS criteria.
Standalone Performance: The Synovasure LFT achieved a sensitivity of 89.5% (95% CI: 78.5-96.1%) and specificity of 94.8% (95% CI: 91.2-97.2%) relative to MSIS PJI Diagnosis.
Key Results:

  • Sensitivity: 89.5% (95% CI: 78.5-96.0%)
  • Specificity: 94.8% (95% CI: 91.2-97.2%)
  • In samples with RBC > 1x10^6/uL excluded (288 samples):
    • Sensitivity: 94.3% (95% CI: 83.9-98.9%)
    • Specificity: 94.5% (95% CI: 90.7-97.1%)

Retrospective Remnant Clinical Samples:
Study Type: Positive Percent Agreement
Sample Size: 65 MSIS positive retrospective samples.
Key Results: The Synovasure LFT exhibited a 98.5% (95% CI: 91.7-100%) positive percent agreement with MSIS diagnosis for these retrospective specimens.

Covariate Analysis (Prospective Study, selected examples):

  • White Subjects (266 samples): Sensitivity 88.2% (76.1-95.6%), Specificity 94.0% (89.9-96.7%)
  • African American Subjects (26 samples): Sensitivity 100% (47.8-100%), Specificity 94.0% (83.9-100%)
  • Male Subjects (excluding RBC>1 x10^6/uL samples, 124 samples): Sensitivity 96.0% (79.6-99.9%), Specificity 90.9% (83.4-95.8%)
  • Female Subjects (excluding RBC>1 x10^6/uL samples, 164 samples): Sensitivity 92.9% (76.5-99.1%), Specificity 97.1% (92.6-99.2%)
  • Subjects with Infection History (excluding RBC>1 x10^9/uL samples, 85 samples): Sensitivity 96.8% (83.3-99.9%), Specificity 88.9% (77.4-95.8%)
  • Subjects with Gram Positive Culture (excluding RBC>1 x10^6/uL samples, 55 samples): Sensitivity 90.6% (75.0-98.0%), Specificity 91.3% (72.0-98.9%)

Key Metrics (Sensitivity, Specificity, PPV, NPV, etc.)

Prospective Study:

  • Sensitivity: 89.5% (95% CI: 78.5-96.0%)
  • Specificity: 94.8% (95% CI: 91.2-97.2%)

Retrospective Study:

  • Positive Percent Agreement: 98.5% (95% CI: 91.7-100%)

Predicate Device(s): If the device was cleared using the 510(k) pathway, identify the Predicate Device(s) K/DEN number used to claim substantial equivalence and list them here in a comma separated list exactly as they appear in the text. List the primary predicate first in the list.

Not Found

Reference Device(s): Identify the Reference Device(s) K/DEN number and list them here in a comma separated list exactly as they appear in the text.

Not Found

Predetermined Change Control Plan (PCCP) - All Relevant Information for the subject device only (e.g. presence / absence, what scope was granted / cleared under the PCCP, any restrictions, etc).

Not Found

§ 866.3230 Device to detect and measure non-microbial analytes to aid in the detection and identification of localized human infections.

(a)
Identification. A device to detect and measure non-microbial analytes to aid in the detection and identification of localized human infections is identified as an in vitro diagnostic device intended for the detection and qualitative measurement, quantitative measurement, or both of one or more non-microbial analytes in human clinical specimens to aid in the assessment, identification, or both of a localized microbial infection when used in conjunction with clinical signs and symptoms and other clinical and laboratory findings.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Any sample collection device used must be FDA-cleared, -approved, or -classified as 510(k) exempt (standalone or as part of a test system) for the collection of human specimens; alternatively, the sample collection device must be cleared in a premarket submission as a part of this device.
(2) The labeling required under § 809.10(b) of this chapter must include:
(i) An intended use with a detailed description of what the device detects and measures, the type of results provided to the user, the sample type, whether the measure is qualitative and/or quantitative, the clinical indications for the test use, and the specific population(s) for which the device is intended.
(ii) A detailed description of the performance characteristics of the device for all intended specimen types from the analytical and clinical studies (as applicable) required under paragraphs (b)(3)(ii) and (iii) of this section.
(iii) A detailed explanation of the interpretation of results, including acceptance criteria for evaluating the validity of individual runs (
e.g., assessment of internal and/or external quality controls, as applicable).(iv) The following limiting statements:
(A) A statement that a negative test result does not preclude the possibility of infection;
(B) A statement that the test results should be interpreted in conjunction with other clinical and laboratory data available to the clinician;
(C) A statement that consistent device performance is dependent on adequate specimen collection, transport, storage, and processing. Failure to observe proper procedures in any one of these steps can lead to incorrect results; and
(D) A statement that details any limitations associated with the samples, as appropriate (
e.g., collected on the day of admission to the intensive care unit).(3) Design verification and validation must include the following:
(i) A detailed device description, including as appropriate, all device parts; control elements incorporated into the test procedure; instrument requirements; reagents required but not provided; and the principle of device operation and test methodology, including all preanalytical methods for the processing of specimens and the methodology from obtaining a sample to the result; design of primer/probe sequences; rationale for target analyte selection; and computational path from collected raw data to reported result (
e.g., how collected raw signals are converted into a reported result).(ii) Detailed documentation of analytical studies including analytical sensitivity (Limit of Detection, Limit of Quantitation, and Limit of Blank), inclusivity, cross-reactivity, microbial interference, interfering substances, competitive inhibition, carryover/cross-contamination, specimen stability, within-lab precision, reproducibility, and linearity, as applicable.
(iii) Detailed documentation and results either from a clinical study, that includes prospective (sequentially collected) samples for each intended specimen type that are representative of the intended use populations and, when determined to be acceptable by FDA, additional characterized clinical samples; or, when determined to be acceptable by FDA, an equivalent sample set. The clinical study must compare the device performance to results obtained from an FDA-accepted reference method and/or FDA-accepted comparator method, as appropriate. Documentation from the clinical studies must include the clinical study protocol (
e.g., the predefined statistical analysis plan), clinical study report, testing results, and results of all statistical analyses.(iv) An evaluation of the level of the non-microbial analyte in asymptomatic patients with demographic characteristics (
e.g., age, racial, ethnic, and sex distribution) similar to the intended use population of the device.(v) Documentation of an appropriate end user device training program that will be offered as part of efforts to mitigate the risks of false results, failure to operate the device correctly, and failure to interpret test results correctly.
(vi) An appropriate risk mitigation strategy to ensure that the device does not prevent any other device(s) with which it is indicated for use, including incorporated device(s), from achieving their intended use (
e.g., safety and effectiveness of the functions of the indicated device(s) remain unaffected).(vii) A detailed description of the impact of any software, including software applications and hardware-based devices that incorporate software, on the device's functions.

0

EVALUATION OF AUTOMATIC CLASS III DESIGNATION FOR SYNOVASURE ALPHA DEFENSIN LATERAL FLOW TEST KIT DECISION SUMMARY

A. De Novo Number:

DEN180032

B. Purpose for Submission:

De Novo request for evaluation of automatic class III designation for the Synovasure Alpha Defensin Lateral Flow Test Kit.

C. Measurand:

Human Alpha Defensins 1-3

D. Type of Test:

Lateral flow immunoassay

E. Applicant:

CD Diagnostics, a Zimmer Biomet Subsidiary

F. Proprietary and Established Names:

Synovasure Alpha Defensin Lateral Flow Test Kit; Synovasure Alpha Defensin Lateral Flow Test Kit (5 Test); Synovasure Alpha Defensin Lateral Flow Test Kit (10 Test); Synovasure Alpha Defensin Lateral Flow Test Kit (30 Test); Synovasure Alpha Defensin Control Kit;

G. Regulatory Information:

    1. Regulation section:
      21 CFR 866.3230
    1. Classification:
      Class II

1

3. Product code(s):

QGN

    1. Panel:
      Microbiology (83)

H. Intended Use:

    1. Intended use(s):
      The Synovasure Alpha Defensin Lateral Flow Test Kit is a qualitative visually read immunochromatographic assay for the detection of human host response proteins, Alpha Defensins 1-3, in the synovial fluid of adults with a total joint replacement who are being evaluated for revision surgery. The Synovasure Alpha Defensin Lateral Flow Test Kit results are intended to be used in conjunction with other clinical and diagnostic findings as an aid in the diagnosis of periprosthetic joint infection (PJI). The Synovasure Alpha Defensin Lateral Flow Test Kit is not intended to identify the etiology or severity of a PJI.

The Synovasure Alpha Defensin Control Kit is used in the Synovasure Alpha Defensin Lateral Flow Test Kit as assayed quality control samples to monitor performance and reliability of the Synovasure Alpha Defensin Lateral Flow Test Kit.

    1. Indication(s) for use:
      Same as intended use.
    1. Special conditions for use statement(s):
      For prescription use only.

For in vitro diagnostic use only.

    1. Special instrument requirements:
      Not applicable.

I. Device Description:

The Synovasure Alpha Defensin Lateral Flow Test Kit (Synovasure LFT) is an immunoassay for the detection of alpha defensin levels in the synovial fluid of patients with a potential PJI. Antibodies specific to alpha defensin bind host alpha defensin in the synovial fluid, become immobilized on the lateral flow test strip, and are detected as a colored line due to the use of a colloidal gold reporter.

2

Synovasure Alpha Defensin Lateral Flow Test Kit contains two sub components:

    1. Synovasure Alpha Defensin Lateral Flow Test Device
    1. Synovasure Lateral Flow Sample Prep Assembly

The Synovasure Lateral Flow Sample Prep Assembly further contains

    1. One Synovasure Dilution Buffer Bottle
    1. One Sample Cup
    1. Two Microsafe Tubes

The Synovasure Alpha Defensin Lateral Flow Test Device is a cassette that includes a reagent strip. Each cassette contains a reagent strip with all the critical components for the assay.

The Synovasure Alpha Defensin Lateral Flow Test Kit is accompanied by the Synovasure Alpha Defensin Control Kit. The Synovasure Alpha Defensin Control Kit further contains

    1. Synovasure Alpha Defensin Positive Control
    1. Synovasure Alpha Defensin Negative Control
    1. Synovasure Control Reconstitution Bottle

The positive control contains 0.25 mL of 16 µg/mL alpha defensin in synthetic synovial fluid and the negative control contains 0.25 mL of synthetic synovial fluid.

Additional materials required but not provided include

  1. Timer

J. Standard/Guidance Document Referenced (if applicable):

EP05-A3, Evaluation of Precision of Quantitative Measurement Procedures; Approved Guideline—Third Edition

EP07-A2, Interference Testing in Clinical Chemistry; Approved Guideline-Second Edition

EP12-A2, User Protocol for Evaluation of Qualitative Test Performance; Approved Guideline-Second Edition

3

EP14-A3, Evaluation of Commutability of Processed Samples; Approved Guideline-Third Edition

EP25-A , Evaluation of Stability of In Vitro Diagnostic Reagents; Approved Guideline

EP28-A3c, Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Guideline-Third Edition

K. Test Principle:

Alpha defensins are antimicrobial peptides secreted by neutrophils in response to infection. The Synovasure Alpha Defensin Lateral Flow Test detects the presence of alpha defensin in synovial fluid specimens utilizing lateral flow technology. A sample of the synovial fluid is diluted and added to the lateral flow test device. The first pad in the device filters out the cellular material and the filtered sample contacts the buffering pad that contains the components for blocking and pH control. The sample then migrates to the pad containing the anti-alpha defensin antibody which is labeled with a colloidal gold conjugate. Finally, the sample mixture migrates to the which has immobilized anti-alpha defensin antibody and then to the control line that captures unbound antibody and verifies that the device flowed properly. A line present in the test zone indicates a positive result and the absence of a line in the test zone indicates a negative result.

L. Performance Characteristics (if/when applicable):

    1. Analytical performance:
    • a. Precision/Reproducibility:

The precision study was performed at three external laboratories over a minimum of 5 days with 3 operators per site. 3 runs per day, 3 reagent lots, and 18 blinded samples per run consisting of 2-4 blinded replicates of each sample. Combined results are shown in Table 1.

4

| Panel Member | % Positive | 95%
Confidence
Interval | % Negative | 95%
Confidence
Interval |
|---------------|--------------------|-------------------------------|--------------------|-------------------------------|
| Negative | 1.0% (4/403) | 0.3-2.5% | 99.0%
(399/403) | 97.5-99.7% |
| High Negative | 9.9% (40/404) | 7.2-13.2% | 90.1%
(364/404) | 86.8-92.8% |
| Cutoff | 49.9%
(202/405) | 44.9-54.9% | 50.1%
(203/405) | 45.1-55.1% |
| Low Positive | 79.9%
(321/403) | 75.4-83.5% | 20.3% (82/403) | 16.5-24.6% |
| Positive | 96.0%
(388/404) | 93.6-97.7% | 4.0% (16/404) | 2.3-6.4% |
| High Positive | 98.5%
(396/402) | 96.8-99.5% | 1.5% (6/402) | 0.5-3.2% |

Table 1: Synovasure LFT Precision of Alpha Defensin Spiked into Synthetic Synovial Fluid

The low positive sample results failed to meet an acceptance criterion of 90% reactivity. To identify a root cause for this discrepancy, a sub-analysis was performed on data stratified form each site and obtained from each operator. The sponsor noted that data obtained from Operators 2 and 3 from Site 1 exhibited significantly lower reactivities in the low positive samples (Table 2). Furthermore, it was noted that the the actual concentration of some panel members was lower than expected due to an error in the preparation of the panel.

| Panel Member | % Positive
Site 1 | 95%
Confidence
Interval | % Positive
Site 2 | 95%
Confidence
Interval | % Positive
Site 3 | 95%
Confidence
Interval |
|---------------|----------------------|-------------------------------|----------------------|-------------------------------|----------------------|-------------------------------|
| Negative | 0.7% (1/134) | 0-4.1% | 1.5%
(2/135) | 0.2-5.2% | 0.7%
(1/134) | 0.0-4.1% |
| High Negative | 0.0% (0/135) | 0-2.7% | 3.7%
(5/134) | 1.2-8.5% | 25.9%
(35/135) | 18.8-34.2% |
| Cutoff | 25.2%
(34/135) | 18.1-33.4% | 51.9%
(70/135) | 43.1-60.5% | 72.6%
(98/135) | 64.3-79.9% |
| Low Positive | 66.4%
(89/134) | 57.8-74.3% | 80.0%
(108/135) | 72.3-86.4% | 92.5%
(124/134) | 86.7-96.4% |
| Positive | 93.3%
(126/135) | 87.7-96.9% | 97.0%
(131/135) | 92.6-99.2% | 97.8%
(131/134) | 93.6-99.5% |
| High Positive | 97.8%
(132/135) | 93.6-99.5% | 99.2%
(132/133) | 95.9-100% | 98.5%
(132/134) | 94.7-99.8% |

Table 2: Precision Performance Stratified by Site

An additional analysis was performed excluding the low positive data from Operators 2 and 3 at Site 1 and the low positive sample reactivity becomes 87% (271/315). According to the probit regression obtained in the C5-C95 study, this is in close agreement with the expected reactivity (88.14%) for the actual alpha defensin concentration of the low positive panel member (10.3 ug/mL). Furthermore, the

5

positive and negative control kit includes an alpha defensin concentration near the LoD and could provide an adequate control for user test interpretation.

  • b. Linearity/assay reportable range:
    Not applicable

  • c. Traceability, Stability, Expected values (controls, calibrators, or methods):
    Stability

External Controls

To monitor the assay performance, reagent performance, and procedural errors, positive and negative external controls must be run in accordance with the guidelines or requirements of local, state, and/or federal regulations or accrediting organizations. The positive and negative controls are packaged lyophilized. Prior to use, the end user rehydrates the lyophilized pellets using the reconstitution fluid provided in the Synovasure Control Reconstitution Bottle following the instructions in the Synovasure Alpha Defensin Control Kit package insert.

Reagent Stability:

Reagent Integral Stability:

The sponsor evaluated the effect of freeze-thaw cycles on Synovasure LFT devices over time. While not reflective of the recommended storage temperatures (2-30°C) for assay components, the product may experience freezing and thawing during transport. A total of 30 Synovasure LFT kits (including the device and buffer bottle with sample cup and Microsafe tube) were stored at -20°C for one week and thawed at room temperature to evaluate performance of spiked synthetic synovial fluid positive and negative controls (N = 10). Additionally, another set of 30 Synovasure LFT kits were stored at -20°C for 24 h. thawed, and returned to -20°C for at least another 24 h three times. Performance of the Synovasure LFT against three synthetic synovial fluid quality control (QC) samples is reported below in Table 3.

6

| 3X Freeze-Thaw

Percent Positive (N)
QC1 (0 ug/mL)QC2 (4 ug/mL)QC3 (12 ug/mL)
0% (0/10)0% (0/10)90% (9/10)
RT Controls
0% (0/3)0% (0/3)100% (3/3)
1X Freeze-Thaw
Neg. ControlPos. Control
0% (0/10)100% (10/10)
RT Controls
0% (0/3)100% (3/3)

Table 3: Synovasure LFT Kit Freeze-Thaw Stability

Three lots of Synovasure LFT assay kits were subjected to real-time stability testing at both 2-8°C and 30°C over a period of either 1021. 990. or 772 days. Positive (16 ug/mL alpha defensin) and negative controls from the associated control kit were evaluated at each time point. Assay performance was evaluated by comparison to a color card unit scale with scores 90% with lower confidence bound of >85% and a specificity criterion of >90% with a lower confidence bound of >90% for combined prospective and retrospective data.

Study Demographics

A total of 386 subjects were evaluated for prospective study eligibility. 81 subjects were excluded because there was insufficient information for an MSIS diagnosis, the subject did not have a total knee or hip arthroplasty, the subject did not have revision surgery, the subject had a joint injection or synovial fluid collection recently, or there was insufficient sample volume for testing. The clinical study therefore analyzed a total of 305 prospective synovial fluid samples and 65 retrospective fresh remnant samples. The sponsor provided the demographic breakdown for prospective clinical study samples as identified in Table 13.

13

VariableValue
Age (years)
Mean64.8
STDEV9.76
Min.38
Max.92
Gender (n, %)
Male131 (43.0%)
Female174 (57.0%)
Race (n, %)
White266 (87.2%)
Asian1 (0.3%)
African American26 (8.5%)
Native American2 (0.7%)
Other10 (3.3%)
Infection History (n, %)
Yes87 (28.5%)
No218 (71.5%)
Antibiotic History (n, %)
Yes40 (13.1%)
No77 (25.2%)
Inflammatory Medications
within the last month (n, %)
Yes43 (14.1%)
No262 (85.9%)
Immunocompromised
Conditions (n, %)
Yes19 (6.2%)
No286 (93.8%)
Medical History (n, %)
Yes219 (71.8%)
No86 (28.2%)

Table 13: Prospective Clinical Study Demographics and Baseline Characteristics

External Controls

During the conduct of the clinical trial protocol, external control testing was performed once per week per operator performing lateral flow testing. The tests were conducted per kit instructions and no control failures were observed over the 74 weeks of clinical testing across all sites.

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Enrollment Inclusion/Exclusion Criteria

The prospective clinical study had the following subject inclusion criteria:

    1. Subject had a total knee and/or hip joint arthroplasty
    1. Subject was evaluated for revision surgery
  • a. Operative samples were required for full MSIS classification
    1. Subject was >22 years of age
    1. Subject had no recent injections or surgeries of the joint (within past 6 weeks)
    1. Subject had all the medical tests required to allow MSIS classification
    1. Subject signed informed consent form.

The prospective clinical study had the following subject exclusion criteria:

    1. Subject did not have a total knee and/or hip joint arthroplasty
    1. Healthy subject without medical need for aspiration
    1. Subject did not have a revision surgery
    1. Subject had a diagnostic synovial fluid specimen collection within the past 14 days
    1. Subject was 20%

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dilution by volume) (Table 15). Out of 17 samples with greater than 20% whole blood contamination, 1 was a true positive, 3 were false negatives, and 13 were true negatives. To address this risk of generating false results, a specific limitation noting the potential for false negative results in samples containing a significant amount of blood is listed in the package insert.

Table 15: Clinical Performance of Synovasure LFT in Prospective Clinical Specimens (RBC>1x106/uL excluded)

MSIS Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP501363
N3222225
Total53235288

Two false negative Synovasure LFT results from the clinical trial were identified in patients with a draining sinus tract connecting to the joint. One of these was also identified as contaminated with greater than 20% whole blood. A draining sinus should be readily observable and is also a major diagnostic criterion for PJI: therefore. the impact of this on the patient's diagnosis would be minimal.

Retrospective Remnant Clinical Samples

To supplement the testing of fresh prospectively collected specimens. the sponsor also obtained fresh retrospective synovial fluid collections to bring the total number of positive specimens tested to at least 100. The residual samples were anonymized. assigned new case ID numbers and tested. Synovasure LFT results were compared to a status determination based positive confirmation of three minor MSIS criteria (neutrophil %, positive culture, and WBC count). A total of 65 MSIS positive retrospective samples were evaluated interspersed with sufficient negative specimens to maintain relative disease prevalence consistent with what was observed in the prospective study population. The Synovasure LFT exhibited a 98.5% (95% CI: 91.7-100%) positive percent agreement with MSIS diagnosis for these retrospective specimens.

Synovasure LFT Analysis of Covariates

Performance of the Synovasure LFT in the prospective clinical study was further assessed among several covariates which could potentially impact device performance: age, gender, race, history of infection, history of inflammatory disease, use of anti-inflammatory medication. gram positive or gram negative culture isolates. type of prosthetic joint, and individual MSIS criteria. Insignificant differences in assay performance were observed based upon these variables (Table 16 - Table 32).

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MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP451358
N6202208
Total51215266
Sensitivity (95% CI): 88.2% (76.1-95.6%)
Specificity (95% CI): 94.0% (89.9-96.7%)

Table 16: Prospective Study Performance of Synovasure LFT for White Subjects

Table 17: Prospective Study Performance of Synovasure LFT for African American Subjects

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP505
N02121
Total52126
Sensitivity (95% CI): 100% (47.8-100%)
Specificity (95% CI): 94.0% (83.9-100%)
Table 18: Prospective Study Performance of Synovasure LFT for Other Races
MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP101
N01212
Total11213
Sensitivity (95% CI): 100% (2.5-100%)
Specificity (95% CI): 100% (73.5-100%)
  1. Other races include Asian, American Indian or Alaskan Native, and races identified as "Other"

Table 19: Prospective Study Performance of Synovasure LFT for Male Subjects (excluding RBC>1 x106 /uL samples)

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP24933
N19091
Total2599124
Sensitivity (95% CI): 96.0% (79.6-99.9%)
Specificity (95% CI): 90.9% (83.4-95.8%)

Table 20: Prospective Study Performance of Synovasure LFT for Female Subjects (excluding RBC>1 x106/μL samples)

MSIS PJI Diagnosis
PNTotal
SynovasureP26430
Lateral FlowN2132134

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TestTotal28136164
Sensitivity (95% CI): 92.9% (76.5-99.1%)
Specificity (95% CI): 97.1% (92.6-99.2%)

To evaluate whether prior infections impact device performance, assay results were tabulated among patients with any prior history of infection or infectious disease (e.g., sinusitis, pneumonia or other respiratory infections, urinary tract infections, the common cold, HIV, lyme disease, viral hepatitis, etc.) within the last 6 months (Table 21) and for for those without such history (Table 22).

Table 21: Prospective Study Performance of Synovasure LFT for Subjects with Infection History (excluding RBC>1 x109/μL samples)

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP30636
N14849
Total315485
Sensitivity (95% CI): 96.8% (83.3-99.9%)
Specificity (95% CI): 88.9% (77.4-95.8%)

Table 22: Prospective Study Performance of Synovasure LFT for Subjects without Infection History (excluding RBC>1 x106 /uL samples)

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP20727
N2174176
Total22181203
Sensitivity (95% CI): 90.9% (70.8-98.9%)
Specificity (95% CI): 96.1% (92.2-98.4%)

Ongoing use of antibiotics might reduce infection severity and affect the performance of the Synovasure Lateral Flow test. Assay sensitivity and specificity were evaluated among study subjects who were actively on an antibiotic regimen upon study enrollment (Table 23) and those not currently taking antibiotic medications (Table 24).

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MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP25126
Synovasure
Lateral Flow
TestN11213
Synovasure
Lateral Flow
TestTotal261339
Sensitivity (95% CI): 96.2% (83.3-99.9%)
Specificity (95% CI): 92.3% (64.0-99.8%)

Table 23: Prospective Study Performance of Synovasure LFT for Subjects with Ongoing Antibiotic Use (excluding RBC>1 x106/uL samples)

Table 24: Prospective Study Performance of Synovasure LFT for Subjects without
Ongoing Antibiotic Use (excluding RBC>1 x106/µL Samples)
MSIS PJI Diagnosis
PNTotal
SynovasureP8513
Lateral FlowN16061
TestTotal96574
Sensitivity (95% CI): 88.9% (51.8-99.7%)
Specificity (95% CI): 92.3% (83.0-97.5%)

The presence of an underlying inflammatory or autoimmune disease (e.g., rheumatoid arthritis, lupus, diabetes, multiple sclerosis, autoimmune hepatitis, psoriasis, scleroderma, sarcoidosis, etc.) was also evaluated for potential impact on Synovasure LFT performance. Study subjects with a history of any inflammatory disease at least 6 months before enrollment were analysed (Table 25) and compared to those with a medical history of no inflammatory or autoimmune disorders (Table 26).

Table 25: Prospective Study Performance of Synovasure LFT for Subjects with
Inflammatory Disease History (excluding RBC>1 x106/μL samples)
MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP12214
N15253
Total135467
Sensitivity (95% CI): 92.3% (64.0-99.8%)
Specificity (95% CI): 96.3% (87.3-99.5%)

Table 26: Prospective Study Performance of Synovasure LFT for Subjects without Inflammatory Disease History (excluding RBC>1 x109/uL samples)

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP381149
N2170172
Total40181221
Sensitivity (95% CI): 95.0% (83.1-99.4%)

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Specificity (95% CI): 93.9% (89.4-96.9%)

The performance of the Synovasure LFT was also evaluated in subjects who are currently on anti-inflammatory or autoimmune medications (e.g., steroids or immunosuppressants) or have taken such medications in the past 6 months (Table 27) and those subjects who have not taken such medications (Table 28).

Table 27: Prospective Study Performance of Synovasure LFT for Subjects Using Anti-Inflammatory Medication (excluding RBC>1 x106/µL samples)

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP10010
N13031
Total113041
Sensitivity (95% CI): 90.9% (58.7-99.8%)
Specificity (95% CI): 100% (88.4-100%)
Table 28: Prospective Study Performance of Synovasure LFT for Subjects without
Current Anti-Inflammatory Medications (excluding RBC>1 x106/μL samples)
MSIS PJI DiagnosisTotal
PN
Synovasure
Lateral Flow
TestP401353
N2192194
Total42205247
Sensitivity (95% CI): 95.2% (83.8-99.4%)
Specificity (95% CI): 93.7% (89.4-96.6%)

Since alpha defensins are host response proteins, it is possible that their expression level varies depending on the type of organism responsible for the joint infection. Performance of the Synovasure LFT was compared in study subjects who had a gram positive pathogen isolated by culture (Table 29) versus those study subjects with a gram negative pathogen isolated by culture (Table 30).

Table 29: Prospective Study Performance of Synovasure LFT for Subjects with Gram Positive Culture (excluding RBC>1 x106/uL samples)

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP29231
N32124
Total322355
Sensitivity (95% CI): 90.6% (75.0-98.0%)
Specificity (95% CI): 91.3% (72.0-98.9%)

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MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP606
N101
Total707
Sensitivity (95% CI): 85.7% (42.1-99.6%)
Specificity (95% CI): Non-estimable

Table 30: Prospective Study Performance of Synovasure LFT for Subjects with Gram Negative Culture (excluding RBC>1 x106/uL samples)

All of the data from the prospective study (including specimens with greater than 1 x106/uL RBC contamination) were also analyzed to evaluate Synovasure LFT Performance in the presence of a positive culture (Table 31), a key component of MSIS diagnostic criteria, and in samples for which no culture was positive (Table 32).

Table 31: Prospective Study Performance of Synovasure LFT for Subjects with at least one Positive Culture

MSIS PJI Diagnosis
PNTotal
Synovasure
Lateral Flow
TestP36238
N52328
Total412566

Table 32: Prospective Study Performance of Synovasure LFT for Subjects with all Negative Cultures

MSIS PJI DiagnosisTotal
PN
Synovasure
Lateral Flow
TestP151126
N1210211
Total16221237
Sensitivity (95% CI): 93.8% (69.8-99.8%)
Specificity (95% CI): 92.0% (91.3-97.5%)

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Prevalence Analysis

A detailed description of the type of infections observed during the clinical study is provided in Table 33.

Table 33: PJI Prevalence Overall and by Type of Infection for All Prospective Subjects with a Synovial Fluid and/or Tissue Culture Performed

| | Positive PJI
Diagnosis
(N, [%, 95% CI]) | Negative PJI
Diagnosis
(N, [%, 95% CI]) | Total
(N, [%, 95% CI]) |
|------------------------------------------|-----------------------------------------------|-----------------------------------------------|---------------------------|
| Subjects with Gram positive
culture | 35 (61%, 48-74%) | 24 (10%, 6-14%) | 59 (19%, 15-24) |
| Subjects with a Gram Negative
Culture | 7 (12%, 5-24%) | 1 (0%, 0-2%) | 8 (3%, 1-5%) |
| Subjects with a Fungal Culture | 1 (2%, 0-9%) | 1 (0%, 0-2%) | 2 (1%, 0-2%) |
| Subjects with any positive
culture | 41 (72%, 58-83%) | 25 (10%, 7-15%) | 66 (22%, 17-27) |
| Subjects with all negative
cultures | 16 (28%, 17-42) | 221 (90%, 85-93%) | 237 (78%, 73-83%) |
| Total subjects with culture
performed | 57 | 246 | 303 |

  • b. Clinical specificity:
    See section M.3a above.

  • c. Other clinical supportive data (when a. and b. are not applicable):
    See section M.3a above.

    1. Clinical cut-off:
      Not applicable.
    1. Expected values/Reference range:
      Not Applicable

M. Instrument Name:

Not applicable. The device does not utilize an instrument for result generation.

22

N. System Descriptions:

1. Modes of Operation:

Does the applicant's device contain the ability to transmit data to a computer, webserver, or mobile device?

Yes ___________ or No ________________________________________________________________________________________________________________________________________________________

Does the applicant's device transmit data to a computer, webserver, or mobile device using wireless transmission?

Yes ___________ or No X_____

    1. Software:
      FDA has reviewed applicant's Hazard Analysis and software development processes for this line of product types:

Yes ____________ or No _______________________________________________________________________________________________________________________________________________________

The device does not contain any software or instrument components.

    1. Specimen Identification:
      Not applicable.
    1. Specimen Sampling and Handling:
      Not applicable.
    1. Calibration:
      Not applicable.
    1. Quality Control:
      Not applicable.

O. Other Supportive Instrument Performance Characteristics Data Not Covered In The "Performance Characteristics" Section above:

None.

  • P. Proposed Labeling:

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The labeling supports the decision to grant the De Novo request for this device.

O. Identified Risks to Health and Identified Mitigations
Identified Risks to HealthMitigation Measures
Risk of false test resultsCertain device descriptions, performance
characteristics, results interpretation
information, limitations, and study details in
labeling.
Certain device description information,
demographic analysis, validation procedures,
risk mitigation strategies and end user trainings,
and studies.
Collection device specification.
Failure to correctly interpret test resultsCertain device descriptions, performance
characteristics, results interpretation
information, limitations, and study details in
labeling.
Certain demographic analysis, validation
procedures, risk mitigation strategies and end
user trainings, and studies.
Failure to correctly operate the deviceCertain device descriptions, performance
characteristics, results interpretation
information, limitations, and study details in
labeling.
Certain demographic analysis, validation
procedures, risk mitigation strategies and end
user trainings, and studies.
Collection device specification.

R. Benefit/Risk Analysis:

Summary of the Assessment of Benefit

The benefit of the assay is aiding the accurate diagnosis of prosthetic joint infection (PI). Accurate diagnosis of prosthetic joint infection can be helpful to initiate appropriate treatment for prosthetic joint infection, including, but not limited to, antibiotics and revision surgery. Appropriate treatment of PJI can lead to alleviation of symptoms associated with infection and restoration of function. Additionally, appropriate exclusion of a prosthetic joint infection will aid clinicians in deciding to retain existing hardware.

Summary of the Assessment of Risk

The risks associated with the device, when used as intended, are those related to the risk of false test results. failure to correctly interpret the test results, and failure to correctly operate the device.

The risk of a false positive test result is improper patient management, including inappropriate administration of prolonged courses of antibiotics and inappropriate

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explanting of hardware. Inappropriate administration of prolonged courses of antibiotics is associated with toxicity, allergic reactions, and adverse outcomes, including secondary infections such as C. difficile colitis. Inappropriate explanting of hardware may further obscure the anatomy of a joint, decrease function, worsen symptoms, and complicate further surgical manipulation of the joint. The risk of a false positive test is mitigated by the intended use clearly stating that the assay is intended as an adjunct to aid in the diagnosis of infection, in conjunction with other clinical and diagnostic findings.

The risk of a false negative test result is improper patient management, including inappropriate discontinuation of antibiotics or failure to treat a prosthetic joint infection with antibiotics and explanting of infected hardware. Failure to treat a prosthetic joint infection could lead to decreased function of the joint and worsen symptoms of infection. If not treated, a prosthetic joint infection could develop into a more complicated or a systemic infection, including skin and soft tissue infection, acute or chronic osteomyelitis, bacteremia, and/or sepsis. A patient who is symptomatic from a prosthetic joint infection will likely return to care, most likely delaying treatment instead of resulting in a complete failure to diagnose and treat. The risk of a false negative test is mitigated by the fact that this assay is intended as an adjunct to aid in the diagnosis of infection in conjunction with other clinical and diagnostic findings.

Failure to correctly operate the device can lead to false test results. Failure to correctly interpret test results can lead to treatment of a clinically positive patient in the same manner as a false negative test result and a clinically negative patient in the same manner as a false positive test result with the corresponding implications discussed above.

Summary of the Assessment of Benefit-Risk

General controls are insufficient to mitigate the risks associated with the device. However, the probable clinical benefits outweigh the potential risks for the proposed assay, considering the mitigations of the risks provided for in the listed special controls established for this device as well as general controls. The required special controls will help ensure that errors will be uncommon and will facilitate accurate assay implementation and interpretation of results. The clinical performance observed in the clinical trial suggests that errors will be uncommon and that the assay will provide substantial benefits to patients in the diagnosis of prosthetic joint infections and when used in conjunction with other clinical and diagnostic findings.

Patient Perspectives

This submission did not include specific information on patient perspectives for this device.

S. Conclusion

The information provided in this De Novo submission is sufficient to classify this device into class II under regulation 21 CFR 866.3230. FDA believes that the stated special controls, in combination with the applicable general controls, provide a reasonable assurance of the safety and effectiveness of the device type. The device is classified under the following:

25

Product Code(s): QGN Device Type: Device to detect and measure non-microbial analytes to aid in the detection and identification of localized human infections Class: II (special controls) Regulation: 21 CFR 866.3230

  • (a) Identification: A device to detect and measure non-microbial analytes to aid in the detection and identification of localized human infections is identified as an in vitro device intended for the detection and qualitative measurement, quantitative measurement, or both of one or more non-microbial analytes in human clinical specimens to aid in the assessment, identification, or both of a localized microbial infection when used in conjunction with clinical signs and symptoms and other clinical and laboratory findings.
  • (b) Classification: Class II (special controls). The special controls for this device are:
      1. Any sample collection device used must be FDA-cleared. -approved, or -classified as 510(k) exempt (standalone or as part of a test system) for the collection of human specimens; alternatively, the sample collection device must be cleared in a premarket submission as a part of this device.
      1. The labeling required under 21 CFR 809.10(b) must include:
      • i. An intended use with a detailed description of what the device detects and measures, the type of results provided to the user, the sample type, whether the measure is qualitative and/or quantitative, the clinical indications for the test use, and the specific population(s) for which the device is intended.
      • A detailed description of the performance characteristics of the device for all ii. intended specimen types from the analytical and clinical studies (as applicable) required under paragraphs 3(ii) and 3(iii).
      • iii. A detailed explanation of the interpretation of results, including acceptance criteria for evaluating the validity of individual runs (e.g., assessment of internal and/or external quality controls, as applicable).
      • iv. The following limiting statements:
        • A statement that a negative test result does not preclude the possibility (A) of infection:
        • A statement that the test results should be interpreted in conjunction with (B) other clinical and laboratory data available to the clinician;
        • A statement that consistent device performance is dependent on (C) adequate specimen collection, transport, storage, and processing. Failure

26

to observe proper procedures in any one of these steps can lead to incorrect results; and

  • A statement that details any limitations associated with the samples, as (D) appropriate (e.g., collected on the day of admission to the ICU).
    1. Design verification and validation must include the following:
    • i. A detailed device description, including as appropriate, all device parts; control elements incorporated into the test procedure; instrument requirements; reagents required but not provided; and the principle of device operation and test methodology, including all pre-analytical methods for the processing of specimens and the methodology from obtaining a sample to the result; design of primer/probe sequences; rationale for target analyte selection; and computational path from collected raw data to reported result (e.g., how collected raw signals are converted into a reported result).
    • ii. Detailed documentation of analytical studies including analytical sensitivity (Limit of Detection, Limit of Quantitation, and Limit of Blank), inclusivity, crossreactivity, microbial interference, interfering substances, competitive inhibition, carryover/cross-contamination, specimen stability, within-lab precision, reproducibility, and linearity, as applicable.
    • iii. Detailed documentation and results either from: a clinical study, that includes prospective (sequentially collected) samples for each intended specimen type that are representative of the intended use populations and, when determined to be acceptable by FDA, additional characterized clinical samples; or, when determined to be acceptable by FDA, an equivalent sample set. The clinical study must compare the device performance to results obtained from an FDA accepted reference method and/or FDA accepted comparator method, as appropriate. Documentation from the clinical studies must include the clinical study protocol (e.g., the predefined statistical analysis plan), clinical study report, testing results, and results of all statistical analyses.
    • iv. An evaluation of the level of the non-microbial analyte in asymptomatic patients with demographic characteristics (e.g., age, racial, ethnic, and gender distribution) similar to the intended use population of the device.
    • Documentation of an appropriate end user device training program that will be V. offered as part of efforts to mitigate the risks of false results, failure to correctly operate the device, and failure to correctly interpret test results.
    • An appropriate risk mitigation strategy to ensure that the device does not prevent vi. any other device(s) with which it is indicated for use, including incorporated device(s), from achieving their intended use (e.g., safety and effectiveness of the functions of the indicated device(s) remain unaffected).

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  • vii. A detailed description of the impact of any software, including software applications and hardware-based devices that incorporate software, on the device's functions.