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510(k) Data Aggregation
(619 days)
WOUNDCHEK Bacterial Status (WCBS) is an in vitro diagnostic chromatographic test for the qualitative detection of bacterial protease activity directly from wound fluid samples collected with a swab. The WCBS test is intended for use in adult patients as an aid in assessing the risk for non-healing of chronic venous, diabetic foot, and pressure ulcers associated with wounds where there are no signs of wound infection and where patients are asymptomatic for clinical signs of infection. The test is intended for use with chronic wounds that are between 21 days and < 6 months of age and chronic wounds that are > 6 months of age that are < 1cm² in size.
This test is indicated for use solely by health care professionals whose clinical practice primarily or routinely involves the assessment and treatment of chronic wounds. WCBS results are intended for use in conjunction with the assessment of other known risk factors for wound healing that significantly contribute to the assessment of risk for nonhealing chronic wounds such as wound age, wound size, and vascular status.
WOUNDCHEK Bacterial Status (WCBS) is a lateral flow assay that qualitatively detects bacterial protease activity in chronic wound fluid. Wound fluid is collected by rolling a swab over the cleansed wound surface until it is saturated. The swab is then incubated in the assay reagent which contains a substrate that can be cleaved by bacterial proteases and human neutrophil elastase (HNE) and an HNE inhibitor. The WCBS test card is used to detect cleavage products of the substrate. It consists of biotinylated bovine serum albumin (BSA) (Test Line (T)), and a control system protein, (Control line (C)), on a nitrocellulose membrane support. Neutravidin, which is conjugated to visualizing particles, binds the biotinylated end of a synthetic peptide and the biotinylated BSA test line. The test result is based on the presence or absence of a pink-to-purple colored Test Line (T) which means bacterial protease activity was detected. A negative test result is defined by the absence of a Test Line (T) which means bacterial protease activity was not detected. If the control line (C) is not present, then the test result is invalid. The device is intended for use on venous leg ulcers (VLU), diabetic foot ulcers (DFU) and pressure ulcers (PU).
A control kit, consisting of negative and positive swabs, is also available for WOUNDCHEK Bacterial Status.
Here's an analysis of the acceptance criteria and the study that proves the WOUNDCHEK Bacterial Status device meets these criteria, based on the provided text:
Acceptance Criteria and Device Performance
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria Category | Specific Criteria | Reported Device Performance and Evidence |
|---|---|---|
| Precision | >95% agreement with expected results for moderate positive, low positive, and true negative panel members. Acceptable variability for high negative panel member. No significant differences in detection rate by site, operator, or day. | Met.Results from a three-site, three-operator study (total 9 operators) showed: - Moderate Positive: 98.5% (133/135) agreement- Low Positive: 95.6% (129/135) agreement- True Negative: 97.8% (132/135) agreementThe high negative panel member had 93.3% (126/135) agreement, acknowledged as variable but acceptable given its nature. No significant differences by site, operator, or day were reported. |
| Sample Stability | Testing of all positive and negative swabs for various storage conditions (up to 9 hours at 2-8°C and 30°C) generated expected results. | Met.Ten positive and negative swabs were tested for each storage condition (0.5, 1, 1.5, 2, 4, 6, 9 hours at 2-8°C and 30°C). All generated expected results. Interpretations were made by two blinded operators, with a total of (b)(4) determinations per condition. Daily controls met expectations. |
| Detection Limit (LOD) | LOD defined as the level of bacterial protease activity generating a positive result ~95% of the time (C95). C5 level also identified. | Met.Preliminary and confirmed LODs (C95, C5, C50) were established for individual proteases (V8, GelE, ZapA, LasB) and a pooled mix of these proteases, consistent with the objective of defining these detection levels. (Specific mU/test values are redacted but are reported as being established). |
| Cross-reactivity - Human Proteases | Positive swabs must produce a positive result in the presence of any host protease. Negative swabs must produce a negative result in the presence of any host protease. | Met.The study identified specific concentrations of human proteases (e.g., MMP-13, MMP-9, HNE, Plasmin) at which no interference was observed with WCBS performance for both positive and negative samples. If initial levels showed interference, dilutions were tested until criteria were met. |
| Interference - Microbial | Positive swabs (with analyte) must produce a positive result in the presence of tested microorganisms. Negative swabs must produce a negative result in the presence of tested microorganisms. | Met.The study determined specific levels of various fungi, mold, and viruses (e.g., Candida species, Aspergillus fumigatus, Herpes Simplex viruses) at which no interference was observed. If initial levels showed interference with stock solutions, log dilutions were tested until criteria were met. |
| Interference - Healthy Skin Flora | Implied: Device should ideally not react to normal skin flora unless these flora are indicative of bacterial protease activity leading to non-healing. However, the study identified that performance is affected by normal skin flora. This led to a labeling mitigation. | Met (with mitigation).Out of (b)(4) apparently healthy skin swab samples, 20 were positive by both operators, and an additional 4 by one operator, totaling 44 false positives out of 102 readings. While the device is affected, this finding is acknowledged as expected due to skin flora secreting proteases. The mitigation is a prominent instruction in the IFU: "Do not swab intact skin." |
| Interfering Substances | Positive swabs must produce a positive result in the presence of the interfering substance. Negative swabs must produce a negative result in the presence of the interfering substance. | Met.The study identified specific concentrations for a wide range of wound-related substances (e.g., acetic acid, silver dressings, Manuka honey, mupirocin, blood, various antibiotics, skin substitutes, iodine, antifungals) at which no interference was observed. If a substance failed at the initial level, it was diluted twofold until criteria were met. |
| Clinical Performance (Risk Assessment for Non-Healing) | Provide Positive Likelihood Ratio (PLR) and Negative Likelihood Ratio (NLR) for indication. | Met (with caveats).For the intended use population (wounds < 6 months old or ≥ 6 months old and < 1 cm²): - PLR = 2.06 (95% CI = 1.25 - 3.41)- NLR = 0.69 (95% CI = 0.54 - 0.88)A positive WCBS result resulted in a 16.6% increased risk of non-healing, and a negative result a 9.4% decreased risk. The study acknowledges limitations in establishing a clear correlation with healing due to its observational design and lack of control for numerous clinical factors or interventions. |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size (Clinical Study - Evaluable): 147 unique wound fluid samples from 139 unique subjects. (Initial enrollment was 350 wounds, reduced due to various exclusions, including 66 wounds from a subpopulation not supported by the claims).
- Data Provenance: Prospective observational study conducted in 2016 at seven (7) sites in the U.S.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications
- Number of Experts: The clinical healing status (healed or not healed) was "assessed by the treating clinician." The text does not specify a number of experts or their explicit qualifications beyond being "treating clinicians" at the study sites. This implies that the clinical decision of "healed" or "not healed" served as the primary ground truth, based on their medical judgment and defined criteria.
- Qualifications: "Treating clinician" with an implied expertise in wound care, as the studies involved "health care professionals whose clinical practice primarily or routinely involves the assessment and treatment of chronic wounds."
4. Adjudication Method for the Test Set
- Clinical Study: Not explicitly stated for the "healing status" ground truth. It was "assessed by the treating clinician." This suggests a single clinician's assessment rather than a multi-reader adjudication process for the final outcome.
- Analytical Studies (e.g., Stability, Cross-reactivity, Interference): Results were typically interpreted by "two operators (each blinded to each other's results)" for a total of 10 or (b)(4) determinations. "Any discrepant results between the operators for a given sample type was clarified by a third operator." This indicates a 2+1 adjudication method.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
- No, an MRMC comparative effectiveness study was not done. The clinical study was an observational study comparing the device's results to the clinical healing status over time. It did not involve a direct comparison of human readers with and without AI assistance or a comparison of improvement in human reader performance. Its purpose was to evaluate the device's performance as an aid in assessing risk for non-healing, not to measure human reader effectiveness.
6. Standalone (Algorithm Only) Performance
- Yes, a standalone performance was done. The entire clinical study (L.3.a) describes the performance of the WOUNDCHEK Bacterial Status (WCBS) device in isolation against the clinical healing status. The WCBS is a lateral flow assay and does not involve AI or a "human-in-the-loop" for its immediate result generation from the swab. The results (PLR, NLR) directly reflect the device's diagnostic capability.
7. Type of Ground Truth Used (Clinical Study)
- Outcomes Data/Expert Clinical Assessment: The ground truth for the clinical study was the "clinical healing status of the wounds," defined as "complete wound closure" (skin re-epithelialization without drainage or dressing requirements) assessed by the treating clinician within a time frame of up to 12 weeks. This is effectively an outcome-based ground truth determined by expert clinical observation.
8. Sample Size for the Training Set
- Not Applicable / Not Provided for Device Training: The WOUNDCHEK Bacterial Status is described as a lateral flow chromatographic assay. This type of in vitro diagnostic device does not typically involve "training data" in the sense of machine learning algorithms. Its design and cutoff are established through analytical studies (e.g., LOD, specificity, cross-reactivity) using predefined panels and controls, not a "training set" of patient data. The provided document details analytical verification and clinical validation.
9. How Ground Truth for the Training Set Was Established
- Not Applicable: As mentioned above, this device does not use a "training set" in the machine learning context. The "ground truth" for its analytical performance validation was established through controlled laboratory experiments using known concentrations of bacterial proteases, human proteases, microorganisms, and interfering substances. The "ground truth" for the clinical validation was the objective observation of wound healing by treating clinicians.
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