(90 days)
The ACON® Strep A Twist Rapid Test Device is a rapid chromatographic immunoassay for the qualitative detection of Strep A antigen from throat swab specimens to aid in the diagnosis of Group A Streptococcal infection. This test is indicated for professional and point of care use only.
The ACON® Strep A Twist Rapid Test Device is a qualitative, lateral flow immunochromatographic assay for the detection of Strep A antigen from a throat swab. The test is a heterogeneous, sandwich immunoassay, based on the principle of antigen-antibody immunochemistry, which uses a mixture of polyclonal antibodies to reliably produce a visually discernible colored line in the test region if Strep A antigen is present at a concentration of roughly 2.5 x 102 organisms per swab or greater.
Here's a breakdown of the acceptance criteria and the study proving the device meets them, based on the provided text:
Acceptance Criteria and Device Performance
| Acceptance Criteria (from predicate device comparison) | Reported Device Performance (ACON Strep A Twist Rapid Test Device) |
|---|---|
| Intended Use: Rapid chromatographic immunoassay for qualitative detection of Strep A antigens from throat swab specimens to aid in diagnosis of Group A Streptococcal infection. | Meets: "a rapid chromatographic immunoassay for the qualitative detection of Strep A antigen from throat swab specimens to aid in the diagnosis of Group A Streptococcal infection." |
| Indications for Use: Professional & point of care use. | Meets: "professional and point of care use only." |
| Intended Specimen: Throat Swab | Meets: "from throat swab specimens" |
| Endpoint: Colored Lines | Meets: Device produces "a visually discernible colored line" |
| Methodology: Membrane Particle Assay | Meets: "qualitative, lateral flow immunochromatographic assay" (which is a type of membrane particle assay) |
| Extraction Time: 1 minute | Meets: "1 minute" |
| Test Time: 5 minutes | Meets: "5 minutes" |
| Organism detection: Strep A specific | Meets: "Strep A specific" (demonstrated through specificity study) |
| Sensitivity (compared to culture): Not explicitly stated as a numerical acceptance criterion, but clinical accuracy is evaluated against it. | 90% (86-94% 95% CI) |
| Specificity (compared to culture): Not explicitly stated as a numerical acceptance criterion, but clinical accuracy is evaluated against it. | 94% (92-96% 95% CI) |
| Overall Agreement (compared to culture): Not explicitly stated as a numerical acceptance criterion, but clinical accuracy is evaluated against it. | 93% (91-95% 95% CI) |
| Negative Agreement (compared to predicate): Not explicitly stated as a numerical acceptance criterion, but clinical accuracy is evaluated against it. | 100% (99-100% 95% CI) |
| Positive Agreement (compared to predicate): Not explicitly stated as a numerical acceptance criterion, but clinical accuracy is evaluated against it. | 94% (89-97% 95% CI) |
| Overall Agreement (compared to predicate): Not explicitly stated as a numerical acceptance criterion, but clinical accuracy is evaluated against it. | 98% (97-99% 95% CI) |
| Cross-reactivity: No cross-reactivity with common respiratory pathogens | Meets: "None of the organism demonstrated any cross-reactivity in the test." (20 organisms tested) |
| Interference: No interference from common oral/throat medications or substances. | Meets: "No interference to an expected negative or positive result was observed" (9 substances tested, plus whole blood and mucin) |
| Intra and Inter-assay Variability: Expected results >99% of the time. | Meets: "expected results >99% of the time" |
| Lot-to-Lot Variability: Highly reproducible. | Meets: "highly reproducible" |
| Minimum detectable level: Roughly 2.5 x 10^2 organisms per swab or greater. | Meets: "roughly 2.5 x 10^2 organisms per swab or greater." (also stated in sensitivity study that 7 strains showed ~10^0 and 2 strains showed ~10^1 organisms per swab, within the general magnitude) |
Study Information:
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Sample size used for the test set and the data provenance:
- Sample Size: 758 patient specimens.
- Data Provenance: Multi-center clinical evaluation. The country of origin is not explicitly stated, but the sponsor is located in San Diego, California, suggesting a US-based study. It is a retrospective study, as specimens were collected from "patients presenting with signs and symptoms of pharyngitis."
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Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- The ground truth (Strep A confirmed culture technique) is a laboratory method, not established by human experts in the way a radiologist reads images. Therefore, the concept of "number of experts" and "qualifications of experts" does not directly apply to the primary ground truth methodology used for the clinical accuracy study.
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Adjudication method for the test set:
- Not specified. The study directly compared the ACON® Strep A Twist Rapid Test Device to a "commercially available Strep A test device" (QuickVue In-Line One-Step Strep A) and to "the customary Strep A confirmed culture technique." There is no mention of an adjudication process between different readers or interpretation of the index device.
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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:
- No, an MRMC comparative effectiveness study involving human readers with and without AI assistance was not done. This device is a rapid diagnostic test for direct visualization of colored lines, not an AI-assisted interpretation device. The "multi-center" evaluation refers to where samples were collected, not to multiple human readers interpreting cases.
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If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Yes, the performance data presented (Sensitivity, Specificity, Agreement) for the ACON® Strep A Twist Rapid Test Device are standalone performance metrics. While a human reads the colored lines, the device itself generates the result indicating presence or absence of Strep A. There isn't an "algorithm" per se in the way AI would be considered, but rather a biochemical reaction. The "standalone" here refers to the device's inherent ability to detect the antigen, which is then interpreted by a user.
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The type of ground truth used:
- Primary Ground Truth: Strep A confirmed culture technique. Culture is widely considered the gold standard for diagnosing Group A Streptococcal infection.
- Secondary Comparison: Another commercially available Strep A test device (Quidel QuickVue In-Line One-Step Strep A) was used for agreement comparison.
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The sample size for the training set:
- The provided document does not explicitly mention a separate "training set" for the device's development. This is common for immunochromatographic assays where the device design and antibody selection are based on scientific principles rather than machine learning training data. The "Sensitivity" section mentions evaluating 9 different strains of Strep A to determine minimum detectable levels, which could be considered part of the R&D/optimization phase, but not a formal "training set" in the AI sense.
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How the ground truth for the training set was established:
- As no formal training set is identified in the document (in the context of machine learning), the establishment of ground truth for a training set is not applicable. The development of the device's capabilities would have relied on laboratory testing against known concentrations of Strep A antigens and strains.
§ 866.3740
Streptococcus spp. serological reagents.(a)
Identification. Streptococcus spp. serological reagents are devices that consist of antigens and antisera (excluding streptococcal exoenzyme reagents made from enzymes secreted by streptococci) used in serological tests to identifyStreptococcus spp. from cultured isolates derived from clinical specimens. The identification aids in the diagnosis of diseases caused by bacteria belonging to the genusStreptococcus and provides epidemiological information on these diseases. Pathogenic streptococci are associated with infections, such as sore throat, impetigo (an infection characterized by small pustules on the skin), urinary tract infections, rheumatic fever, and kidney disease.(b)
Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to § 866.9.