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The CorDx Tyfast COVID- 19 Ag Rapid Test is a visually read lateral flow immunoassay device intended for the rapid, qualitative detection of SARS-CoV-2 virus nucleocapsid protein antigen directly in anterior nasal swab specimens from individuals with signs and symptoms of COVID-19.

This test is for non-prescription home use by individuals aged 14 years or older testing themselves, or adults testing individuals aged 2 years or older.

The CorDx Tyfast COVID- 19 Ag Rapid Test does not differentiate between SARS-CoV and SARS-CoV-2.

All negative results are presumptive. Symptomatic individuals with an initial negative test result must be re-tested once between 48 and 72 hours after the first test using an antigen test or a molecular test for SARS-CoV-2. Negative results do not preclude SARS-CoV-2 infections or other pathogens and should not be used as the sole basis for treatment. Positive results do not rule out co-infection with other respiratory pathogens.

This test is not a substitute for visits to a healthcare provider or appropriate follow-up and should not be used to determine any treatments without provider supervision. Individuals who test negative and experience continued or worsening COVID-19 like symptoms, such as fever, cough and/or shortness of breath, should seek follow up care from their healthcare provider.

The performance characteristics for SARS-CoV-2 were established from September, 2023, to December, 2023, when SARS-CoV-2 Omicron was dominant. Test accuracy may change as new SARS-CoV-2 viruses emerge. Additional testing with a lab-based molecular test (e.g., PCR) should be considered in situations where a new virus or variant is suspected.

The CorDx Tyfast COVID-19 Ag Rapid Test is intended for non-prescription self-use and/or as applicable an adult lay user testing another person 2 years of age or older in a nonlaboratory setting.

The CorDx Tyfast COVID-19 Ag Rapid Test is a rapid, immunochromatographic membrane assay that uses highly sensitive monoclonal antibodies to detect nucleocapsid protein from SARS-CoV-2 from anterior nasal swab specimens. This test does not differentiate between SARS-CoV and SARS-CoV-2. The test kit includes the: test cassette, swab, tube with sample processing solution, tube holder (back of the box) and the Quick Reference Instructions (QRI).

The test strip enclosed in a cassette housing is comprised of the following components: sample pad, reagent pad, reaction membrane, and absorbing pad. The reagent pad contains colloidal-gold conjugated with a monoclonal antibody against the nucleocapsid protein of SARS-CoV-2; the reaction membrane contains the secondary antibody for the nucleocapsid protein of SARS-CoV-2. The whole strip is fixed inside a plastic cassette.

When the sample extract is added into the sample well, conjugates dried onto the reagent pad are dissolved and migrate along with the sample. If SARS-CoV-2 nucleocapsid antigen is present in the sample, a complex formed between the anti-SARS-2 conjugate and the viral antigen will be captured by the specific anti-SARS-2 monoclonal antibody coated on the test line region (T). Absence of the test line (T) suggests a negative result. To serve as a procedural control, a red line will always appear in the control line region (C) indicating that proper volume of sample has been added and membrane wicking has occurred.

The CorDx Tyfast COVID-19 Ag Rapid Test is a qualitative lateral flow immunoassay intended for the rapid detection of SARS-CoV-2 virus nucleocapsid protein antigen in anterior nasal swab specimens from individuals with signs and symptoms of COVID-19. It is designed for non-prescription home use by individuals aged 14 years or older testing themselves, or adults testing individuals aged 2 years or older.

1. Acceptance Criteria and Reported Device Performance

The acceptance criteria for the device performance are based on the Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) compared to a highly sensitive 510(k)-cleared SARS-CoV-2 RT-PCR assay.

2. Sample Sizes and Data Provenance

• Test Set Sample Size: 740 individuals were enrolled in the study, with 693 evaluable subjects.
  • True Positives: 101 subjects
  • True Negatives: 572 subjects
  • Discordant Results (Test Negative, Comparator Positive): 17 subjects
  • Discordant Results (Test Positive, Comparator Negative): 3 subjects
• Data Provenance: The clinical study was prospective, conducted from September 2023 to December 2023 at four (4) sites throughout the United States. This indicates the data is prospective and from the USA.
• Training Set Sample Size: The document does not provide specific details on the training set sample size for any machine learning components, as this is a visually read lateral flow immunoassay and not explicitly an AI/ML device in the context of the provided text. The "Precision Study by Lots" used 60 replicates for each of 3 lots (180 total) for negative, 2xLoD, and 4xLoD samples to assess analytical precision and consistency.

3. Number of Experts and Qualifications for Ground Truth

The document does not explicitly state the number of experts or their specific qualifications (e.g., radiologist with 10 years experience) used to establish ground truth. However, the ground truth was established by a "highly sensitive 510(k)-cleared SARS-CoV-2 RT-PCR assay," which is considered the gold standard for SARS-CoV-2 detection. Therefore, the expertise lies in the validated performance of the comparator RT-PCR assay and its operation in a clinical laboratory setting.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method for discordant results in the clinical study beyond simply identifying the discordant cases. The final ground truth was determined by the RT-PCR assay, implying that the RT-PCR result was considered definitive for the purpose of performance calculation.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

A MRMC comparative effectiveness study was not conducted. This device is a visually read rapid antigen test, and the study design focused on the device's performance against a gold standard molecular assay, not on human reader improvement with or without AI assistance.

6. Standalone Performance (Algorithm Only)

Standalone performance (algorithm only) was not explicitly conducted or reported, as this device is a visually read lateral flow immunoassay. Its performance is inherent in its design and the user's interpretation, rather than an independent algorithm.

7. Type of Ground Truth Used

The primary ground truth used for the clinical performance evaluation was a highly sensitive 510(k)-cleared SARS-CoV-2 RT-PCR assay. This is a molecular diagnostic method, considered a definitive reference standard for SARS-CoV-2 infection.

8. Sample Size for the Training Set

As this is a visually read rapid antigen test and not an AI/ML diagnostic system in the conventional sense, a 'training set' for an algorithm is not applicable in the way it would be for an image-based AI system. The analytical performance evaluations would involve internal validation data. For instance, the "Precision Study by Lots" utilized 180 samples in total across three lots for each concentration (negative, 2xLoD, 4xLoD) to demonstrate analytical consistency.

9. How Ground Truth for the Training Set Was Established

Given that this is not an AI/ML device with a distinct 'training set' for an algorithm, the concept of establishing ground truth for a training set in that context is not applicable. For internal analytical studies (like LoD, inclusivity, cross-reactivity, and precision), ground truth was established through:

• Spiking known concentrations of SARS-CoV-2 virus: For LoD and inclusivity studies, UV-inactivated or heat-inactivated SARS-CoV-2 virus (USA-WA1/2020 isolate or specific variants) at defined TCID50/mL or IU/mL concentrations were spiked into negative nasal wash or swab matrix.
• Testing against known common respiratory pathogens/substances: For cross-reactivity and interference studies, known concentrations of various microorganisms or endogenous/exogenous substances were used, both with and without spiked SARS-CoV-2 (at 3x LoD), to assess their impact on test results.
• Use of WHO International Standard: For LoD determination, the WHO International Standard for SARS-CoV-2 Antigen (NIBSC 21/368) was used to ensure traceability.

These methods establish the "ground truth" for the analytical performance characteristics of the device during its development and validation.

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