(27 days)
The Alere™ PBP2a Test is a qualitative, in vitro immunochromatographic assay for the detection of penicillin-binding protein 2a (PBP2a) in isolates identified as Staphylococcus aureus, as an aid in detecting methicillin-resistant Staphylococcus aureus (MRSA). The Alere™ PBP2a Test is not intended to diagnose MRSA nor to guide or monitor treatment for MRSA infections.
The Alere™ PBP2a Test is a rapid immunochromatographic membrane assay that uses highly sensitive monoclonal antibodies to detect the PBP2a protein directly from bacterial isolates. These antibodies and a control antibody are immobilized onto a nitrocellulose membrane as two distinct lines and combined with a sample pad, a blue conjugate pad, and an absorption pad to form a test strip. Isolates are sampled directly from the culture plate and eluted into an assay tube containing Reagent 2 is then added and the dipstick is placed in the assay tube. Results are read visually at 5 minutes.
Acceptance Criteria and Study Details for Alere™ PBP2a Test
1. Table of Acceptance Criteria and Reported Device Performance
The provided document does not explicitly state "acceptance criteria" in a quantitative manner (e.g., "Sensitivity must be >= 95%"). However, the clinical performance study aims to demonstrate substantial equivalence, implying that the observed performance (Sensitivity and Specificity compared to the reference method) was deemed acceptable for market clearance. Based on the "Clinical Performance" section, the performance of the device was evaluated against cefoxitin (30 ug) disk diffusion.
| Metric (Implicit Acceptance Criteria) | Device Performance (Tryptic Soy Agar with 5% sheep blood) | Device Performance (Columbia Agar with 5% sheep blood) | Device Performance (Mueller Hinton with 1 µg oxacillin induction) |
|---|---|---|---|
| Sensitivity | 98.1% (95% C.I. 95.2-99.3%) | 99.0% (95% C.I. 96.6-99.7%) | 99.5% (95% C.I. 97.4-99.9%) |
| Specificity | 98.8% (95% C.I. 96.5-99.6%) | 98.8% (95% C.I. 96.5-99.6%) | 98.8% (95% C.I. 96.5-99.6%) |
| Reproducibility | 97.3% agreement with expected results (580/596) - Overall for all sites | 97.3% agreement with expected results (580/596) - Overall for all sites | 97.3% agreement with expected results (580/596) - Overall for all sites |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Test Set: A total of 457 S. aureus samples were evaluated in the clinical performance study.
- Data Provenance:
- Country of Origin: The clinical performance study was conducted at "three geographically-diverse laboratories." The document explicitly mentions "a collection of strains from Department of Infectious Disease Epidemiology of the Imperial College in London, England" for the analytical performance (analytical reactivity and specificity), which suggests that at least some data or strains originated from outside the US. The main clinical study likely included US sites given the FDA submission, but this is not explicitly stated.
- Retrospective or Prospective: Not explicitly stated. The wording "A total of 457 S. aureus samples were evaluated" does not indicate whether these were prospectively collected or retrospectively analyzed isolates.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications
The document does not specify the number of experts or their qualifications used to establish the ground truth for the test set.
4. Adjudication Method for the Test Set
The document does not specify any adjudication method used for the test set.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not conducted. The study compares the device's performance directly to a reference method (cefoxitin disk diffusion), not the performance of human readers with or without AI assistance.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done
Yes, the study describes the standalone (algorithm only) performance of the device. The Alere™ PBP2a Test is a rapid immunochromatographic membrane assay where results are "read visually at 5 minutes." The performance metrics (Sensitivity and Specificity) are for the device's ability to detect PBP2a compared to the reference method. While a human visually reads the result, the performance assessed is of the diagnostic test itself, not a human interpreting images/data that the device produces.
7. The Type of Ground Truth Used
The ground truth used for the clinical performance study was established by cefoxitin (30 ug) disk diffusion, interpreted according to CLSI (Clinical and Laboratory Standards Institute) standards. This is a recognized laboratory method for determining methicillin resistance in Staphylococcus aureus.
8. The Sample Size for the Training Set
The document does not explicitly state a dedicated "training set" size. The "Analytical Reactivity and Specificity" section mentions testing 162 strains of MRSA and 112 strains of MSSA with expected results to demonstrate analytical performance. While these strains might have informed the development of the device, they are presented as part of an analytical validation rather than a distinct "training set" in the context of machine learning model development. The device described (immunochromatographic assay) is not a machine learning algorithm that requires a traditional training set.
9. How the Ground Truth for the Training Set was Established
As mentioned above, there isn't a "training set" in the machine learning sense. For the strains used in analytical testing (162 MRSA and 112 MSSA), the ground truth (whether they were MRSA or MSSA) was established based on their classification from their source (NARSA, ATCC, and Imperial College collection). These are well-characterized strains with established resistance profiles.
§ 866.1640 Antimicrobial susceptibility test powder.
(a)
Identification. An antimicrobial susceptibility test powder is a device that consists of an antimicrobial drug powder packaged in vials in specified amounts and intended for use in clinical laboratories for determining in vitro susceptibility of bacterial pathogens to these therapeutic agents. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).