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Alere i Strep A 2 is a rapid, instrument-based, molecular in vitro diagnostic test utilizing isothermal nucleic acid amplification technology for the qualitative detection of Streptococcus pyogenes, Group A Streptococcus bacterial nucleic acid in throat swab specimens obtained from patients with signs and symptoms of pharyngitis. It is intended to aid in the rapid diagnosis of Group A Streptococcus bacterial infections.

Alere™ i Strep A 2 is a rapid, instrument-based isothermal test for the qualitative detection of Streptococus pyogenes Group A Strep from throat swab specimens. The Alere™ i Strep A 2 System utilizes isothermal nucleic acid amplification technology and is comprised of:

• . Sample Receiver - single use, disposable containing the elution buffer
• Test Base – single use, disposable comprising two sealed reaction tubes, each containing a lyophilized pellet
• Transfer Cartridge single use, disposable for transfer of the eluted sample to the Test Base, and ●
• . Alere™ i Instrument – repeat use reader

The reaction tubes in the Test Base contain the reagents required for Streptococcus pyogenes Group A Strep bacterial lysis and the subsequent amplification of the target nucleic acid and an internal control. Alere™ i Strep A 2 utilizes a pair of templates (similar to primers) for the specific amplification of DNA from Streptococcus pyggenes, Group A Strep and fluorescently labeled molecular beacons designed to specifically identify the amplified nucleic acid targets. Alere™ i Strep A 2 is performed within the confinement of the Test Base, and no other part of the Alere™ i Instrument has contact with the sample during the amplification process. This reduces the risk of instrument contamination and sample carry-over between measurements.

To perform the assay, the Sample Receiver and Test Base are inserted into the Alere™ i Instrument. The sample is added to the Sample Receiver and transfer Cartridge to the Test Base, resuspending the lyophilized pellets contained within the Test Base and initiating bacterial lysis and target amplification. Heating, mixing and detection by fluorescence is provided by the instrument, with results automatically reported.

Results are displayed by the Alere™ i Instrument and are also stored in an on-board archive and are assigned to a sample ID that has been entered into the Alere™ i Instrument by the operator, and the date/time the test was performed. Data can be retrieved and downloaded by the operator at any time after testing. An external Alere™ Universal Printer can be attached via USB to the Alere™ i Instrument to print test results.

Here's a summary of the acceptance criteria and study details for the Alere™ i Strep A 2 device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The FDA clearance document doesn't explicitly state all "acceptance criteria" as clear numerical thresholds for performance metrics. However, it presents the clinical performance of the device against a comparator method (bacterial culture), and these reported values implicitly demonstrate that the device met the necessary performance expectations for clearance.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size (Clinical Study): 981 evaluable throat swab specimens.
• Data Provenance: Multi-center, prospective clinical study conducted at nine (9) US trial sites in 2017.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications

• The document states that the Alere™ i Strep A 2 performance was evaluated "in comparison to bacterial culture." Bacterial culture is typically performed in a laboratory by trained microbiologists using established protocols. The document does not specify the number of experts, nor their specific qualifications (e.g., years of experience), but implies standard laboratory practices for culture results.
• For discrepancies, a "laboratory developed real-time PCR assay" was used for confirmation. This also implies expert analysis within a laboratory setting, but specific expert details are not provided.

4. Adjudication Method for the Test Set

• The primary ground truth for the clinical study was bacterial culture. In cases of discordance between Alere™ i Strep A 2 and bacterial culture, a "laboratory developed real-time PCR assay" was used for further investigation:
  • 38 of 52 samples positive by Alere™ i Strep A 2 and negative by bacterial culture were positive by PCR.
  • 1 of 3 samples negative by Alere™ i Strep A 2 and positive by bacterial culture was negative by PCR.
• This suggests an implicit adjudication based on a tertiary, highly sensitive method (PCR) for resolving some discrepancies.

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. This device is an in-vitro diagnostic (IVD) molecular test, not an imaging or diagnostic assistant used by human readers in the traditional sense. The output is an automated positive/negative result.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

• Yes, the clinical performance study directly reflects the standalone performance of the device (Alere™ i Strep A 2) without human interpretation affecting the result. The device is "instrument-based" and provides "automated" results. The operator's role is to perform the assay steps, but the diagnostic determination is made by the instrument/algorithm.

7. The Type of Ground Truth Used

• The primary ground truth used for the clinical performance study was bacterial culture of throat swab specimens.
• For discordant results, a laboratory-developed real-time PCR assay was used as a confirmatory method.

8. The Sample Size for the Training Set

• The document does not provide information regarding a specific training set size. For IVD devices, especially molecular diagnostic kits, the "training" (development and optimization) process typically involves internal analytical studies rather than a distinct, prospectively collected "training set" of clinical samples with established ground truth in the same way an AI/ML algorithm might. Clinical studies are primarily for validation.

9. How the Ground Truth for the Training Set Was Established

• As a molecular diagnostic test, the "ground truth" for its development (analogous to a training set for AI) would primarily rely on well-characterized clinical samples and reference strains with known Streptococcus pyogenes status confirmed by methods like culture and sequencing during the assay development and optimization phases. However, the document does not detail this. The provided clinical study serves as the primary validation of the device against bacterial culture as the ground truth.

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