(167 days)
The provided text does not contain any K/DEN numbers listed under the "Reference Device(s)" section. It explicitly states "Not Found".
No
The device description mentions a "real time curve recognition algorithm" for interpreting fluorescent signals, which is a standard signal processing technique and does not indicate the use of AI or ML. The document explicitly states "Mentions AI, DNN, or ML: Not Found".
No
This device is an in vitro diagnostic test used to detect the presence of Streptococcus pyogenes, which aids in the diagnosis of pharyngitis, rather than performing a therapeutic function.
Yes
Explanation: The "Intended Use / Indications for Use" section explicitly states, "The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a qualitative in vitro diagnostic test for the detection of...". Additionally, the "Device Description" section reiterates that it is "a rapid, automated in vitro diagnostic test".
No
The device description clearly outlines a system that includes both hardware (Liat™ Analyzer, Liat™ Tube) and software components. The software is integral to the operation of the hardware and the interpretation of results, but it is not a standalone software-only medical device.
Yes, this device is an IVD (In Vitro Diagnostic).
Here's why:
- Explicitly stated in the Intended Use/Indications for Use: The very first sentence clearly states, "The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a qualitative in vitro diagnostic test..."
- Explicitly stated in the Device Description: The first sentence of the Device Description also states, "The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a rapid, automated in vitro diagnostic test..."
- Performs testing on biological samples: The device analyzes throat swab specimens, which are biological samples.
- Provides diagnostic information: The test detects the presence of Streptococcus pyogenes DNA, which is used to aid in the diagnosis of pharyngitis.
- Intended for use in a laboratory setting: The intended user/care setting is described as "hospital, reference, or state laboratory settings," which are typical environments for IVD testing.
All of these points align with the definition of an In Vitro Diagnostic device.
N/A
Intended Use / Indications for Use
The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a qualitative in vitro diagnostic test for the detection of Streptococcus pyogenes (Group A β-hemolytic Streptococcus, Strep A) in throat swab specimens from patients with signs and symptoms of pharyngitis.
The Liat™ Strep A Assay utilizes nucleic acid purification and polymerase chain reaction (PCR) technology to detect Streptococcus pyogenes by targeting a segment of the Streptococcus pyogenes genome.
Product codes
PGX
Device Description
The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a rapid, automated in vitro diagnostic test for the qualitative detection of Streptococcus pyogenes (Group A B-hemolytic Streptococcus, Strep A) DNA in throat swab specimens in Amies medium.
The Liat™ Strep A Assay targets a well-conserved region of Strep A genome. An Internal Process Control (IPC) is also included. The IPC is present to control for adequate processing of the target bacteria through all steps of the assay process and to monitor the presence of inhibitors in the sample preparation and PCR. The sample-to-result time is ~15 minutes.
The assay utilizes a single-use disposable Liat™ Tube that holds the sample purification and PCR reagents, and hosts the sample preparation and PCR processes. The Liat™ Tube contains all required unit dose reagents pre-packed in tube segments, separated by peelable seals, in the order of reagent use.
The Liat™ Analyzer automates and integrates sample purification, nucleic acid amplification, and detection of the target sequence in biological samples. The Liat™ Analyzer performs all assay steps from clinical sample and reports assay result automatically. During the testing process, multiple sample processing actuators of the analyzer compress the Liat™ Tube to selectively release reagents from tube segments, move the sample from one segment to another, and control reaction volume, temperature, and time to conduct sample preparation, nucleic acid extraction, target enrichment, inhibitor removal, nucleic acid elution and real-time PCR. An embedded microprocessor controls and coordinates the actions of these sample processors to perform all required assay processes within the closed Liat™ Tube.
Positive and negative controls are provided in the Liat™ Strep A Assay Quality Control Kit. The positive control comprises inactivated Strep A bacteria in a dried format. The negative control comprises Amies medium.
To perform the Liat™ Strep A Assay, an operator first collects a throat swab and places the swab into Amies transport medium. The operator transfers the sample into the Liat™ Strep A Assay tube using a transfer pipette, and scans the tube barcode to identify the test and the sample barcode to code the sample ID with the assay run on the Liat™ Analyzer. The Liat™ Tube is then inserted into the Liat™ Analyzer. The analyzer performs all the test steps and outputs interpreted results (e.g. Strep A Detected, Strep A Not Detected) in ~15 minutes. A report of the interpreted results can be viewed on the Liat™ Analyzer's LCD screen, and printed directly through a USB or network connected printer. No reagent preparation or additional steps are required other than adding the sample to the Liat™ Tube. Because all the reagents are contained within the Liat™ assay tube and no sample or reagent needs to be removed from the tube, cross contamination between samples is minimized.
The results are interpreted by the Liat™ Analyzer software from measured fluorescent signals and real time curve recognition algorithm.
Mentions image processing
Not Found
Mentions AI, DNN, or ML
Not Found
Input Imaging Modality
Not Found
Anatomical Site
throat swab specimens
Indicated Patient Age Range
Not Found
Intended User / Care Setting
Not Found
Description of the training set, sample size, data source, and annotation protocol
Not Found
Description of the test set, sample size, data source, and annotation protocol
Not Found
Summary of Performance Studies
Precision/Reproducibility: A Reproducibility Study was performed to assess the total variability of the Liat™ Strep A Assay. The Liat™ assay was evaluated at 3 sites. Two operators at each of the 3 sites tested a 4 member reproducibility panel in triplicate on 5 different days, for a total of 360 runs (4 panel members × 3 replicates × 2 operators × 5 days × 3 sites). Nine (9) Liat™ Analyzers and 3 Liat™ Strep A Assay tube lots were used. The reproducibility panel comprised a negative, a high negative (C5: 0.03X LOD), a low positive (C95: 1X LOD) and a medium positive (C100: 3X LOD) Strep A sample. Total percent agreement was 99.7% for Strep A and 100% for IPC.
Detection Limit: The Limit of Detection (LOD) of the Liat™ Strep A Assay was determined by limiting dilution studies using titered bacteria of 4 Strep A strains. The bacteria were spiked into throat swab sample matrix, and then tested using the Liat™ Strep A Assay. The LOD was determined as the lowest bacterial concentration that was detected ≥95% of the time (i.e. at least 19 out of 20 replicates tested positive). The Liat™ assay detected all strains tested, with an LOD in the range of 5 - 20 CFU/mL, or 1 - 4 CFU/test.
Analytical Specificity (Reactivity): A Reactivity Study was performed to evaluate the ability of the Liat™ Strep A Assay to detect Strep A strains representing temporal and geographical diversity. In addition to those strains tested in LOD study, the Liat™ Strep A Assay was evaluated for reactivity with 5 Strep A strains at 20 - 80 CFU/mL or 4 - 16 CFU/test. The bacteria were spiked into throat swab sample matrix. and then tested using the Liat™ Strep A Assay. The assay detected all strains tested.
Analytical Specificity (Cross-reactivity): A Cross-reactivity Study was performed to evaluate the potential of the Liat™ Strep A Assay to cross-react with other microorganisms that may be present in throat swab samples. The Liat™ assay was evaluated against a panel of 72 microorganisms. Bacteria were tested at ≥10^6 CFU/mL. Viruses were tested at ≥10 TCID50/mL or the highest available concentration. The Liat Strep A Assay showed no cross reactivity with the tested microorganisms.
Interfering Microorganisms: An Interfering Microorganism Study was conducted to evaluate whether other microorganisms that may be present in throat swab samples can interfere with the detection of Strep A by the Liat™ assay. The 72 microorganisms were tested for potential interference with Strep A detection. Bacteria were tested at ≥10^6 CFU/mL, and viruses were tested at ≥10^6 TCID50/mL, or the highest available concentration, in the presence of a Strep A at concentration of 3x LOD in throat swab matrix. Results show that the presence of the tested microorganisms did not interfere with the detection of Strep A.
Interfering Substances: The Liat™ Strep A Assay was evaluated with 28 substances that may be encountered in throat swab specimens. Medically and/or physiologically relevant concentrations of potential interferents were tested in throat swab matrix in the presence and absence of Strep A at 3x LOD. Results showed that none of the substances tested interfered with the Liat™ Strep A Assay.
Carry-over/Cross-contamination: A study was conducted to demonstrate that the single-use, self-contained Liat™ assay tube reduces the risk of carry-over contamination when alternating high positive and negative samples are tested in series. High positive samples comprised of Strep A spiked into negative throat swab matrix at 3.13 × 10^4 CFU/mL, while negative samples comprised negative throat swab matrix. Eighty (80) tests were conducted on 2 Liat™ Analyzers with high positive and negative samples alternating analyzer-to-analyzer and run-to-run. All 40 high positive samples tested were correctly reported as "Strep A Detected". All 40 negative samples tested were correctly reported as "Strep A Not Detected". There was no carry-over or cross contamination observed during this study.
Clinical Sensitivity and Specificity: The Liat™ Strep A Assay was evaluated in December 2013 to April 2014 by six clinical sites representing geographically distinct regions throughout the United States. Clinical specimens (Total: 570) were collected from patients with symptom characteristics of pharyngitis. Performance characteristics of the assay were determined by comparison to culture and latex agglutination for Strep A typing. Discordant results were investigated using PCR and bi-directional sequencing based on published methods. In all cases of "Invalid", "Indeterminate", and "Assay Aborted" results (7 out of 577 total), re-test of the same specimens gave a valid result.
Key Metrics
Sensitivity: 98.3% (170/173)
Specificity: 94.2% (374/397)
Accuracy: 95.4% (544/570)
Prevalence: 30.4% (173/570)
PPV: 88.1% (170/193)
NPV: 99.2% (374/377)
Invalid rate: 1.2% (7/577)
Predicate Device(s)
Reference Device(s)
Not Found
Predetermined Change Control Plan (PCCP) - All Relevant Information
Not Found
§ 866.2680
Streptococcus spp. nucleic acid-based assay.(a)
Identification. AStreptococcus spp. nucleic acid-based assay is a qualitative in vitro diagnostic device intended to simultaneously detect and identify variousStreptococcus spp. nucleic acids extracted directly from clinical specimens. The device detects specific nucleic acid sequences for organism identification. The identification aids in the diagnosis of diseases caused by bacteria belonging to the genusStreptococcus and provides epidemiological information on these diseases. Pathogenic streptococci are associated with infections, such as sore throat, impetigo (an infection characterized by small pustules on the skin), urinary tract infections, rheumatic fever, and kidney disease.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Premarket notification submissions must include detailed device description documentation, including the device components, ancillary reagents required but not provided, and a detailed explanation of the methodology including primer/probe sequence, design, and rationale for sequence selection.
(2) Premarket notification submissions must include detailed documentation from the following analytical and clinical performance studies: Analytical sensitivity (Limit of Detection), reactivity, inclusivity, precision, reproducibility, interference, cross reactivity, carry-over, and cross contamination.
(3) Premarket notification submissions must include detailed documentation from a clinical study. The study, performed on a study population consistent with the intended use population, must compare the device performance to results obtained from well-accepted reference methods.
(4) Premarket notification submissions must include detailed documentation for device software, including, but not limited to, software applications and hardware-based devices that incorporate software.
(5) Premarket notification submissions must include database implementation methodology, construction parameters, and quality assurance protocols, as appropriate.
(6) The device labeling must include limitations regarding the need for culture confirmation of negative specimens, as appropriate.
(7) A detailed explanation of the interpretation of results and acceptance criteria must be included in the device's 21 CFR 809.10(b)(9) compliant labeling.
(8) Premarket notification submissions must include details on an end user device training program that will be offered while marketing the device, as appropriate.
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Food and Drug Administration 10903 New Hampshire Avenue Document Control Center - WO66-G609 Silver Spring, MD 20993-0002
IQUUM INC LINGJUN CHEN COO 700 NICKERSON ROAD MARLBOROUGH MA 01762-4663
November 4, 2014
Re: K141338
Trade/Device Name: Liat Strep A Assav Regulation Number: 21 CFR 866.2680 Regulation Name: Streptococcus spp. nucleic acid based assay Regulatory Class: II Product Code: PGX Dated: October 14, 2014 Received: October 15, 2014
Dear Dr. Chen:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food. Drug. and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21. Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Parts 801 and 809); medical device reporting (reporting of medical device-related adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
1
If you desire specific advice for your device on our labeling regulations (21 CFR Parts 801 and 809), please contact the Division of Industry and Consumer Education at its toll-free number (800) 638 2041 or (301) 796-7100 or at its Internet address
http://www.fda.gov/MedicalDevices/Resourcesfor You/Industry/default.htm. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to
http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.
You may obtain other general information on your responsibilities under the Act from the Division of Industry and Consumer Education at its toll-free number (800) 638-2041 or (301) 796-7100 or at its Internet address
http://www.fda.gov/MedicalDevices/ResourcesforYou/Industry/default.htm.
Sincerely yours,
Uwe Scherf - S for
Sally Hojvat, M.Sc., Ph.D. Director Division of Microbiology Devices Office of In Vitro Diagnostics and Radiological Health Center for Devices and Radiological Health
Enclosure
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Indications for Use
510(k) Number (if known) K141338
Device Name Liat™ Strep A Assay
Indications for Use (Describe)
The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a qualitative in vitro diagnostic test for the detection of Streptococus pyogenes (Group A 8-hemolytic Streptococcus, Strep A) in throat swab specimens from patients with signs and symptoms of pharyngitis.
The Liat™ Strep A Assay utilizes nucleic acid purification and polymerase chain reaction (PCR) technology to detect Streptococcus pyogenes by targeting a segment of the Streptococcus pyogenes genome.
| Type of Use (Select one or both, as applicable) | |
|---|---|
| Prescription Use (Part 21 CFR 801 Subpart D) | Over-The-Counter Use (21 CFR 801 Subpart C) |
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510(K) SUMMARY
October 27, 2014 Summary Date:
510(k) Number: K141338
Purpose for Submission:
The purpose of this submission is the evaluation of the Liat™ Strep A Assay performed on the Liat™ Analyzer for the detection of Streptococcus pyogenes.
Measurand:
The Liat™ Strep A Assay is a rapid, automated in vitro diagnostic test for qualitative detection of S. pyogenes (Group A Streptococcus) from throat swab specimens.
Type of Test:
Nucleic acid assay for qualitative detection of Strep A from throat swab specimens including nucleic acid isolation and real-time PCR amplification using the Liat™ Analyzer.
Applicant:
IQuum, Inc. 700 Nickerson Road Marlborough, MA 01752 Tel: 508-970-0099 Fax: 508-970-0119
Contact: Lingjun Chen Title: Vice President, POC Operational Development Tel: 508-970-0099 ext. 116 Email: lingjun(@iquum.com
Proprietary and Established Names:
Liat™ Strep A Assay
Regulatory Information:
Regulation section:
21 CFR 866.2690, Streptococcus spp. nucleic acid based assay
Classification:
Class II
Product code:
PGX
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Panel:
Microbiology (83)
Intended Use:
Intended use(s):
The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a qualitative in vitro diagnostic test for the detection of Streptococcus pyogenes (Group A ß-hemolytic Streptococcus) in throat swab specimens from patients with signs and symptoms of pharyngitis.
The Liat™ Strep A Assay utilizes nucleic acid purification and polymerase chain reaction (PCR) technology to detect Streptococcus pyogenes by targeting a segment of the Streptococcus pyogenes genome.
Indication(s) for use: Same as Intended Use Special conditions for use statement(s):
For prescription use only
Special instrument requirements:
Requires the Liat™ Analyzer
Device Description:
The Liat™ Strep A Assay, performed on the Liat™ Analyzer, is a rapid, automated in vitro diagnostic test for the qualitative detection of Streptococcus pyogenes (Group A B-hemolytic Streptococcus, Strep A) DNA in throat swab specimens in Amies medium.
The Liat™ Strep A Assay targets a well-conserved region of Strep A genome. An Internal Process Control (IPC) is also included. The IPC is present to control for adequate processing of the target bacteria through all steps of the assay process and to monitor the presence of inhibitors in the sample preparation and PCR. The sample-to-result time is ~15 minutes.
The assay utilizes a single-use disposable Liat™ Tube that holds the sample purification and PCR reagents, and hosts the sample preparation and PCR processes. The Liat™ Tube contains all required unit dose reagents pre-packed in tube segments, separated by peelable seals, in the order of reagent use.
The Liat™ Analyzer automates and integrates sample purification, nucleic acid amplification, and detection of the target sequence in biological samples. The Liat™ Analyzer performs all assay steps from clinical sample and reports assay result automatically. During the testing process, multiple sample processing actuators of the analyzer compress the Liat™ Tube to selectively release reagents from tube segments, move the sample from one segment to another, and control reaction volume, temperature, and time to conduct sample preparation, nucleic acid extraction, target enrichment, inhibitor removal, nucleic acid elution and real-time PCR. An
5
embedded microprocessor controls and coordinates the actions of these sample processors to perform all required assay processes within the closed Liat™ Tube.
Positive and negative controls are provided in the Liat™ Strep A Assay Quality Control Kit. The positive control comprises inactivated Strep A bacteria in a dried format. The negative control comprises Amies medium.
To perform the Liat™ Strep A Assay, an operator first collects a throat swab and places the swab into Amies transport medium. The operator transfers the sample into the Liat™ Strep A Assay tube using a transfer pipette, and scans the tube barcode to identify the test and the sample barcode to code the sample ID with the assay run on the Liat™ Analyzer. The Liat™ Tube is then inserted into the Liat™ Analyzer. The analyzer performs all the test steps and outputs interpreted results (e.g. Strep A Detected, Strep A Not Detected) in ~15 minutes. A report of the interpreted results can be viewed on the Liat™ Analyzer's LCD screen, and printed directly through a USB or network connected printer. No reagent preparation or additional steps are required other than adding the sample to the Liat™ Tube. Because all the reagents are contained within the Liat™ assay tube and no sample or reagent needs to be removed from the tube, crosscontamination between samples is minimized.
The results are interpreted by the Liat™ Analyzer software from measured fluorescent signals and real time curve recognition algorithm. All possible final test results are described below.
| Strep A | IPC | |||||
|---|---|---|---|---|---|---|
| Report Results | PCR Result | Curve Pattern | PCR Result | Curve Pattern | Interpretation | |
| 1 | Strep A Not Detected | — | + | OK | Negative test for Strep A | |
| (no Strep A DNA detected) | ||||||
| 2 | Strep A Detected | + | OK | ± | Positive test for Strep A | |
| (Strep A DNA present) | ||||||
| 3 | Strep A Indeterminate. | |||||
| Repeat Assay. | + | Abn | ± | Presence or absence of Strep | ||
| A cannot be determined. | ||||||
| Repeat assay with same | ||||||
| sample or, if possible, new | ||||||
| sample. | ||||||
| 4 | Assay Invalid. Repeat | |||||
| Assay | — | + | Abn | Presence or absence of Strep | ||
| A cannot be determined. | ||||||
| Repeat assay with same | ||||||
| sample or, if possible, new | ||||||
| sample. | ||||||
| 5 | Assay Aborted | [N/A] | [N/A] | [N/A] | [N/A] | Presence or absence of Strep |
| A cannot be determined. | ||||||
| Repeat assay with same | ||||||
| sample or, if possible, new | ||||||
| sample. |
Interpretation of Results from the Liat™ Analyzer
Note: Abn = Abnormal
If the test result is "Indeterminate" or "Invalid", repeat the assay with the same patient specimen, or if possible, collect a new specimen from the patient and repeat the assay using the new
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specimen. Specimens that have repeat "Indeterminate" or "Invalid" results should be sent to a laboratory for confirmatory testing.
If an assay is aborted due to run error, or if an assay is aborted by user, repeat the test with the same sample or, if possible, a new sample. Contact IQuum Technical Support if repeat "Errors" are reported.
Substantial Equivalence Information:
Predicate device name(s):
Quidel Lyra™ Direct Strep Test
Predicate 510(k) number(s):
Comparison with predicate:
| Similarities | ||
|---|---|---|
| Item Name | Liat™ Strep A | Lyra™ Direct Strep |
| Intended Use | The Liat™ Strep A Assay, performed | |
| on the Liat™ Analyzer, is a qualitative | ||
| in vitro diagnostic test for the detection | ||
| of Streptococcus pyogenes (Group A β- | ||
| hemolytic Streptococcus ) in throat swab | ||
| specimens from patients with signs and | ||
| symptoms of pharyngitis. |
The Liat Strep A Assay utilizes nucleic
acid purification and polymerase chain
reaction (PCR) technology to detect
Streptococcus pyogenes by targeting a
segment of the Streptococcus pyogenes
genome. | The Lyra™ Direct Strep Assay is a
Real-Time PCR in vitro diagnostic test
for the qualitative detection and
differentiation of Group A β-hemolytic
Streptococcus ( Streptococcus pyogenes )
and pyogenic Group C and G β-
hemolytic Streptococcus nucleic acids
isolated from throat swab specimens
obtained from patients with signs and
symptoms of pharyngitis, such as sore
throat. The assay does not differentiate
between pyogenic Groups C and G β-
hemolytic Streptococcus .
All negative test results should be
confirmed by bacterial culture, because
negative results do not preclude Group
A, C or G Strep infection and should not
be used as the sole basis for treatment.
The assay is intended for use in
hospital, reference, or state laboratory
settings. The device is not intended for
point-of-care use. |
| Regulation | 21 CFR 866.2690 | (same) |
| Product Code | PGX | (same) |
| Assay Target | Streptococcus A | Streptococcus A, C/G |
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| Similarities | ||
|---|---|---|
| Item Name | LiatTM Strep A | LyraTM Direct Strep |
| Sample Type | Throat swab | (same) |
| Internal Control | Yes | Yes |
| Strep A Target | Conserved sequence within the genome | |
| of S. pyogenes | Conserved regions within the genomes | |
| of group A streptococci and group C/G | ||
| streptococci. | ||
| Assay Method | PCR for detecting the presence / | |
| absence of bacterial DNA in clinical | ||
| specimens | (same) | |
| Detection | ||
| Technique | Different reporter dyes for target and | |
| Internal Control | (same) | |
| Assay Result | Qualitative | (same) |
| Differences | ||
|---|---|---|
| Item Name | Liat™ Strep A | Lyra™ Direct Strep |
| Extraction | ||
| Method | Automated silica-magnetic bead-based nucleic acid extraction and purification | Manual heat lysis |
| Equipment | ||
| Required | Liat™ Analyzer | • ABI 7500 Fast Thermocycler |
| • Plate centrifuge for 96 well plate | ||
| • Heat block | ||
| • Thermometer | ||
| • Timer | ||
| • Micropipette | ||
| Automation | Yes: integrated computer controlled sample processing and PCR amplification/detection | No: manual sample processing and PCR set-up |
| Reagents / Kit | ||
| Components | • Unitized Liat™ Strep A Assay Tube | |
| • Transfer pipette | • Unitized Process Buffer for heat lysis | |
| • Bulk PCR Master Mix | ||
| • Bulk Rehydration Solution for Master Mix | ||
| Reagent Format | • Unitized ready for use | |
| • Manual reagent manipulation NOT required | • Bulk reagents | |
| • Manual pipetting required | ||
| Result | ||
| Interpretation | Automated | Manual |
| Time-to-result | ~15 minutes | ~70 minutes |
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Test Principle:
The Liat™ Strep A Assay uses an established nucleic acid test chemistry and assay protocol for bacterial DNA detection. The sample preparation methodology is based on chaotropic agentbased lysis and silica magnetic bead-based nucleic acid purification. First, the throat swab sample in Amies medium is mixed with an internal process control (IPC) comprising a chemically-inactivated bacterium. Chaotropic and proteolytic reagent then disrupts the three dimensional structure in macromolecules such as proteins and nucleic acids in the sample, and denatures them. Second, nucleic acids are isolated from the lysate through binding to the surface of silica magnetic beads in the presence of a chaotropic salt, which removes water from hydrated molecules in solution. Third, the beads are separated from the lysate using a magnetic field, and the lysate is removed. Fourth, the beads with captured nucleic acids are washed to remove possible inhibitors in the sample. Finally, the captured nucleic acids are then eluted under lowsalt conditions into a small volume of elution buffer.
Target amplification and detection uses TaqMan probe-based real-time PCR. The Strep A primer and probe set is designed for the detection of a conserved sequence within the genomes of Strep A bacteria. An IPC primer and probe set is also included to amplify the target region of the IPC bacterium.
Eluted bacterial DNA undergoes PCR where the reaction mixture is repeatedly heated to denature the nucleic acid and cooled to allow annealing of primers and extension of annealed primers by DNA polymerase to logarithmically amplify a specific region of the DNA. Duallabeled fluorogenic hydrolysis (TagMan) probes anneal to specific target sequences located between the binding regions of forward and reverse primers. During the extension phase of the PCR cycle, the 5' nuclease activity of polymerase degrades the probes, causing the reporter dyes to separate from the quenchers, thus generating fluorescent signals. Fluorescence intensities are monitored at each PCR cycle.
The Liat™ Analyzer automatically interprets the results from measured fluorescent signals. Embedded calculation algorithms determine the PCR cycle threshold (Ct) and evaluate the Ct and fluorescence endpoint against the valid range to generate a positive or negative PCR result. Additionally, pattern recognition algorithms inspect the PCR curves to determine if the curve pattern is within specification or abnormal.
All these sample preparation, real-time PCR amplification, and result interpretation processes are conducted in a closed Liat™ Tube in ~15 minutes.
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Performance Characteristics:
Analytical performance:
Precision/Reproducibility:
A Reproducibility Study was performed to assess the total variability of the Liat™ Strep A Assay across operators, study sites, testing days, Liat™ Analyzers, and Liat™ assay tube lots. The Liat™ assay was evaluated at 3 sites. Two operators at each of the 3 sites tested a 4 member reproducibility panel in triplicate on 5 different days, for a total of 360 runs (4 panel members × 3 replicates × 2 operators × 5 days × 3 sites). Nine (9) Liat™ Analyzers and 3 Liat™ Strep A Assay tube lots were used. The reproducibility panel comprised a negative, a high negative (C5: 0.03X LOD), a low positive (C95: 1X LOD) and a medium positive (C100: 3X LOD) Strep A sample. For the negative and high negative samples, the expected result was negative; for the low positive and medium positive samples the expected result was positive.
The tables below show the reproducibility results for Strep A and the Internal Process Control (IPC). Total percent agreement was 99.7% for Strep A and 100% for IPC.
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| Strep A Reproducibility Results | |
|---|---|
| --------------------------------- | -- |
| Site | 1 | 2 | 3 | Total | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sample | Agreement | Ct Avg | Ct %CV | Amp Avg | Amp %CV | Agreement | Ct Avg | Ct %CV | Amp Avg | Amp %CV | Agreement | Ct Avg | Ct %CV | Amp Avg | Amp %CV | Agreement | Ct Avg | Ct %CV | Amp Avg | Amp %CV | 95% CI |
| Neg. | 30/30 | - | - | - | - | 30/30 | - | - | - | - | 30/30 | - | - | - | - | 90/90 (100%) | - | - | - | - | 95.9% - 100.0% |
| C5 | 30/30 | - | - | - | - | 30/30 | - | - | - | - | 30/30 | - | - | - | - | 90/90 (100%) | - | - | - | - | 95.9% - 100.0% |
| C95 | 29/30 | 29.4 | 2% | 1.8 | 29% | 30/30 | 29.8 | 4% | 1.5 | 44% | 30/30 | 29.2 | 3% | 1.8 | 32% | 89/90 (99%) | 29.5 | 3% | 1.7 | 35% | 94.0% - 99.8% |
| C100 | 30/30 | 27.2 | 2% | 3.2 | 10% | 30/30 | 27.9 | 2% | 2.8 | 14% | 30/30 | 26.8 | 2% | 3.2 | 8% | 90/90 (100%) | 27.3 | 3% | 3.0 | 12% | 95.9% - 100.0% |
| Total Agreement | 119 / 120 (99.2%) | 120 / 120 (100%) | 120 / 120 (100%) | 359 / 360 (99.7%) | 98.4%- 100.0% |
Amp = Endpoint fluorescence value
IPC Reproducibility Results
| Site | 1 | 2 | 3 | Total | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sample | Agreement | Ct | Amp | Agreement | Ct | Amp | Agreement | Ct | Amp | Agreement | Ct | Amp | 95% CI | ||||||||
| Avg | %CV | Avg | %CV | Avg | %CV | Avg | %CV | Avg | %CV | Avg | %CV | Avg | %CV | Avg | %CV | ||||||
| Neg. | 30/30 | 29.0 | 2% | 2.9 | 13% | 30/30 | 29.0 | 2% | 2.9 | 12% | 30/30 | 29.1 | 2% | 2.8 | 12% | 90/90 | |||||
| (100%) | 29.0 | 2% | 2.9 | 13% | 95.9% - | ||||||||||||||||
| 100.0% | |||||||||||||||||||||
| C5 | 30/30 | 28.8 | 2% | 3.0 | 13% | 30/30 | 29.1 | 2% | 2.9 | 15% | 30/30 | 29.1 | 2% | 2.7 | 16% | 90/90 | |||||
| (100%) | 29.0 | 2% | 2.9 | 15% | 95.9% - | ||||||||||||||||
| 100.0% | |||||||||||||||||||||
| C95 | 30/30 | 28.9 | 2% | 3.0 | 11% | 30/30 | 28.8 | 2% | 2.9 | 10% | 30/30 | 29.1 | 1% | 2.6 | 10% | 90/90 | |||||
| (100%) | 28.9 | 2% | 2.8 | 12% | 95.9% - | ||||||||||||||||
| 100.0% | |||||||||||||||||||||
| C100 | 30/30 | 28.5 | 2% | 2.7 | 12% | 30/30 | 28.8 | 2% | 2.7 | 11% | 30/30 | 28.7 | 2% | 2.2 | 16% | 90/90 | |||||
| (100%) | 28.7 | 2% | 2.5 | 15% | 95.9% - | ||||||||||||||||
| 100.0% | |||||||||||||||||||||
| Total | |||||||||||||||||||||
| Agreement | 120 / 120 (100%) | 120 / 120 (100%) | 120 / 120 (100%) | 360 / 360 (100%) | 98.9- | ||||||||||||||||
| 100.0% |
Amp = Endpoint fluorescence value
11
Controls:
The Liat Strep A Assay has 3 controls: (1) internal process control, (2) positive control and (3) negative control.
Internal Process Control
The internal process control (IPC) comprises an inactivated bacterium that is pre-packed in each Liat™ tube. When conducting an assay, the IPC is first mixed with sample and then goes through all the test processes to monitor both the sample processing and PCR performance. The IPC DNA is detected in a separate channel by IPC specific primers and probe. If IPC target Ct and fluorescence endpoint are not above a minimum value and Strep A is not detected, the assay run report indicates "Assay Invalid. Repeat test" to avoid false negative results due to excessive sample inhibition or system operation outside the normal range.
Positive Control
The positive control is provided in the Liat™ Strep A Assay QC Kit. The positive control comprises inactivated Strep A bacteria in a dried format. The target level for the positive control is designed to be close to the LOD of the assay.
To use the positive control, an operator transfers the Amies medium contained in the Dilution Amies tube into the positive control tube using a transfer pipette to rehydrate and mix the dried positive control, and then transfers the entire mixture into the Liat™ Tube. The Liat™ Tube is then run on a Liat™ Analyzer according to the Package Insert.
The positive control is required to be run during the "Add Liat™ Tube Lot' process, in which the Liat™ Tube lot and end user site procedures are checked at the end user site. Additional positive control runs may be performed by the end-user to confirm the performance of a Liat™ Analyzer and a Liat™ Tube lot through detection of S. pyogenes target DNA, or as required by the end user's quality control standards.
Negative Control
The negative control is provided in the Liat™ Strep A Assay QC Kit. The negative control comprises Amies medium. The solution is provided in unit dose quantity and labeled as Dilution Amies.
To use the negative control, an operator transfers the Amies media directly into the Liat™ Tube using a transfer pipette and runs the assay following the Package Insert.
The negative control is required to be run during the "Add Liat™ Tube Lot' process, in which potential contamination and end user site procedures are checked at the end user site. Additional negative control runs may be performed by the end-user to check if there is contamination resulting in a false positive result, or as required by the end user's quality control standards.
12
Detection Limit:
The Limit of Detection (LOD) of the Liat™ Strep A Assay was determined by limiting dilution studies using titered bacteria of 4 Strep A strains. The bacteria were spiked into throat swab sample matrix, and then tested using the Liat™ Strep A Assay. The LOD was determined as the lowest bacterial concentration that was detected ≥95% of the time (i.e. at least 19 out of 20 replicates tested positive). The Liat™ assay detected all strains tested, with an LOD in the range of 5 - 20 CFU/mL, or 1 - 4 CFU/test.
| LOD | ||||||
|---|---|---|---|---|---|---|
| Strain | CFU/mL | CFU/test | ||||
| ATCC BAA-946 | 5 | 1 | ||||
| ATCC 12370 | 10 | 2 | ||||
| ATCC BAA-1066 | 10 | 2 | ||||
| ATCC 700294 | 20 | ব |
Analytical Specificity (reactivity):
A Reactivity Study was performed to evaluate the ability of the Liat™ Strep A Assay to detect Strep A strains representing temporal and geographical diversity. In addition to those strains tested in LOD study, the Liat™ Strep A Assay was evaluated for reactivity with 5 Strep A strains at 20 - 80 CFU/mL or 4 - 16 CFU/test. The bacteria were spiked into throat swab sample matrix. and then tested using the Liat™ Strep A Assay. The assay detected all strains tested.
| Strain | Test Concentration | Strep A Result | |
|---|---|---|---|
| CFU/mL | CFU/test | ||
| ATCC 700497 | 20 | 4 | + |
| ATCC 700949 | 20 | 4 | + |
| ATCC 700499 | 40 | 8 | + |
| ATCC 21548 | 40 | 8 | + |
| ATCC 10403 | 80 | 16 | + |
Analytical Specificity (Cross-reactivity):
A Cross-reactivity Study was performed to evaluate the potential of the Liat™ Strep A Assay to cross-react with other microorganisms that may be present in throat swab samples. The Liat™ assay was evaluated against a panel of 72 microorganisms. Bacteria were tested at ≥10° CFU/mL. Viruses were tested at ≥10 TCID