(52 days)
IDI-MRSA™ assay is a qualitative in vitro diagnostic test for the direct detection of nasal colonization by methicillin-resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test performed on the Smart Cycler® instrument with a nasal swab specimen from patients at risk for colonization, utilizes polymerase chain reaction (PCR) for the amplification of MRSA DNA and fluorogenic target-specific hybridization probes for the detection of the amplified DNA.
IDI-MRSA is not intended to diagnose MRSA infections nor to guide or monitor treatment for Concomitant cultures are necessary only to recover organisms for MRSA infections. epidemiological typing or for further susceptibility testing.
A nasal specimen is collected and transported to the laboratory using the Copan Venturi Transystem®. For testing, the swab is placed in sample preparation buffer. The specimen is concentrated and lysed. An aliquot of the lysate is added to PCR reagents which contain the MRSA-specific primers used to amplify the genetic target [a sequence near the insertion site of Staphylococcal Cassette Chromosome mec (SCCmec)], if present. The assay also includes an internal control (IC) used to detect PCR inhibitory specimens and to confirm the integrity of assay reagents in negative specimens. Amplified targets are detected with hybridization probes labeled with quenched fluorophores (molecular beacons). The amplification, the detection of fluorescence and the interpretation of signals are done automatically by the Smart Cycler® instrument. The whole processed takes about 60 to 75 minutes, depending on the number of specimens processed. This is in addition to specimen preparation which takes about 15 minutes. If appropriate, culture media can be inoculated during specimen preparation or up to 24 hours after its preparation.
Here's a breakdown of the acceptance criteria and study information for the Infectio Diagnostic Inc. IDI-MRSA™ assay, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The submission describes a Special 510(k) for modifications to an already cleared device. Therefore, the "acceptance criteria" are primarily established against the performance of the original, cleared formulation of the IDI-MRSA™ assay. The reported device performance indicates equivalence to the original.
| Parameter | Acceptance Criteria (inferred from "Equivalent to original formulation" and "Meets claims") | Reported Device Performance |
|---|---|---|
| Validation of cut-off | Equivalent to original formulation | Equivalent to original formulation |
| Verification of amplified products | Nucleic acids equivalent to their theoretical sizes (as per original) | Estimated number of nucleic acids equivalent to their theoretical sizes |
| Limit of detection | Equivalent to original formulation | Equivalent to original formulation |
| Analytical sensitivity towards different MREJ polymorphic groups | Equivalent to original formulation | Equivalent to original formulation |
| Validation of analytical specificity | Equivalent to original formulation | Equivalent to original formulation |
| Potentially interfering substances | Equivalent to original formulation | Equivalent to original formulation |
| Performance with clinical specimens (Sensitivity) | Meets claims (of original formulation) | Sensitivity meets claims |
| Performance with clinical specimens (Specificity) | Meets claims (of original formulation) | Specificity meets claims |
| Performance with clinical specimens (Rate of unresolved specimens) | Equivalent to original formulation | Rate of unresolved specimens equivalent to original formulation |
| Performance with clinical specimens (Results agreement with original) | >96% agreement with original formulation | Results agreement with original formulation >96% |
| Reproducibility | Meets claims (of original formulation) | Meets claims |
2. Sample Size Used for the Test Set and Data Provenance
The document does not explicitly state the specific sample size used for the test set of clinical specimens. It only mentions "Performance with clinical specimens" and provides results for sensitivity, specificity, unresolved specimens, and agreement with the original formulation.
The data provenance is not explicitly stated regarding country of origin or whether it was retrospective or prospective. However, given it's a Special 510(k) for modifications, it's highly probable the clinical specimen testing involved comparing the modified assay's performance against the original assay on a set of existing (retrospective) and/or newly collected (prospective) clinical samples.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
This information is not provided in the document. For an in vitro diagnostic test like this, the "ground truth" for clinical specimens would typically be established by established microbiological culture methods, often interpreted by clinical microbiologists or infectious disease specialists. However, the document does not detail this process or the number/qualifications of experts involved.
4. Adjudication Method for the Test Set
This information is not provided in the document. Given the nature of a PCR-based assay, adjudication for "ground truth" in the context of clinical specimens usually involves standard microbiological culture results, not expert consensus on the device's output itself.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance
A Multi-Reader Multi-Case (MRMC) comparative effectiveness study is not applicable to this device. The IDI-MRSA™ assay is a standalone in vitro diagnostic test that provides a qualitative result (detection of MRSA DNA). There is no "human reader" interpreting the output in the same way as, for example, a radiologist interprets an imaging scan. Therefore, there's no concept of human readers improving with or without "AI assistance" in this context.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done
Yes, a standalone performance study was implicitly done. The IDI-MRSA™ assay is a fully automated system from detection of fluorescence to interpretation of signals by the Smart Cycler® instrument. The comparison study evaluated the modified assay's direct output (detection of MRSA DNA) against the original formulation. The assay itself performs the "algorithm" for positive/negative determination.
7. The Type of Ground Truth Used
For the "Performance with clinical specimens," the ground truth is implicitly microbiological culture results, which is considered the gold standard for detecting Staphylococcus aureus and determining methicillin resistance. The document states: "Concomitant cultures are necessary only to recover organisms for epidemiological typing or for further susceptibility testing," which suggests culture is the comparator, though not explicitly called the "ground truth" for the performance metrics.
8. The Sample Size for the Training Set
The document does not specify a separate "training set" or its sample size. For an IVD like this, analytical validation and optimization might involve various bacterial strains and spiked samples (which could be considered part of a development/training phase), but a distinct "training set" in the machine learning sense is not described. The studies primarily focus on validating the modified assay against the original cleared assay's performance characteristics.
9. How the Ground Truth for the Training Set was Established
As no explicit "training set" is described, the method for establishing its ground truth is not provided. However, for analytical parameters like Limit of Detection, Analytical Sensitivity, and Specificity, the ground truth would be established by carefully characterized bacterial isolates, known concentrations of target DNA, and well-identified non-target organisms.
§ 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).