(93 days)
The Wondfo Strep A Rapid Test is a chromatographic immunoassay for the qualitative detection of Strep A antigen from throat swab specimens from symptomatic patients to aid in the diagnosis of Group A Streptococcal Infection. All negative test results should be confirmed by bacterial culture because negative results do not preclude Group A Strep infection and should not be used as the sole basis for treatment. The test is intended for professional and laboratory use, only.
For in vitro diagnostic use For prescription Use only
Wondfo One Step Strep A Swab Test is a qualitative, lateral flow immunoassay for the detection of Strep A carbohydrate antigen directly from a throat swab sample. To perform the test. Reagent 1 (R 1) is added to the extraction tube which is coated with a mixture of conjugate antibodies and a lytic enzyme extraction reagent.
The lytic enzyme is mixed with colloidal gold conjugated to rabbit anti-Strep A and a second colloidal gold control conjugate antibody. The reagents are dried onto the bottom of an extraction tube forming a red spot. The extraction/conjugate pellet is re-suspended with RI and the throat swab is added to the extraction tube. The Strep A antigen is extracted from the sample and the swab is removed. The test strip is immediately placed in the extracted sample.
If Group A Streptococcus is present in the sample, it will react with the anti-Strep A antibody conjugated to the gold particle. The complex will then be bound by the anti-Strep A capture antibody and a visible red test line will appear, indicating a positive result. To serve as an onboard procedural control, the blue line observed at the control site prior to running the assay will turn red, indicating that the test has been performed properly. If Strep A antigen is not present, or present at very low levels, only a red control line will appear. If the red control line does not appear, or remains blue, the test result is invalid.
Acceptance Criteria and Study for Wondfo One Step Strep A Swab Test
This document outlines the acceptance criteria and the performance study for the Wondfo One Step Strep A Swab Test, a chromatographic immunoassay for the qualitative detection of Strep A antigen.
1. Table of Acceptance Criteria and Reported Device Performance
| Parameter | Acceptance Criteria (Stated or Implied) | Reported Device Performance |
|---|---|---|
| Clinical Sensitivity (All Ages) | - Implied to be clinically acceptable (compared to predicate device's 96.2%) | 95% (95% CI: 88%-98%) |
| Clinical Specificity (All Ages) | - Implied to be clinically acceptable (compared to predicate device's 98.7%) | 98% (95% CI: 96%-99%) |
| Precision (C95 Concentration) | 95.0% detection at C95 concentration | Overall Detection: 95.0% (171/180) |
| Precision (Moderate Positive) | 100% detection | Overall Detection: 100% (180/180) |
| Precision (True Negative) | 0% detection (no false positives) | Overall Detection: 0% (0/180) |
| Analytical Sensitivity (Cut-off) | Defined as the concentration at 95% detection | 1.5 x 10^5 organisms/mL (95.2% detection) |
| Interference | No false positives or false negatives observed with tested substances at specified concentrations | No false positive or false negative results shown at tested concentrations |
| Analytical Specificity (Cross-reactivity) | No cross-reactivity with tested organisms at 1x10^8 organisms/mL | No cross-reactivity found for listed organisms |
2. Sample Size Used for the Test Set and Data Provenance
- Test Set (Clinical Study): A total of 349 throat swabs were collected.
- 101 culture-positive specimens.
- 248 culture-negative specimens.
- Data Provenance: The document does not explicitly state the country of origin. The study appears to be prospective, as samples were "collected from patients exhibiting symptoms of pharyngitis" and then tested by both culture and the Wondfo device.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
- The ground truth for the clinical study was established by bacterial culture on sheep blood agar plates. It is a laboratory-based method of detecting bacterial presence, not based on expert interpretation of images or observations.
- Therefore, the concept of "number of experts" and "qualifications of those experts" in the traditional sense of medical image interpretation (e.g., radiologists) is not applicable here. The culture results are considered the objective ground truth.
4. Adjudication Method for the Test Set
- The ground truth was established by bacterial culture. This is an objective laboratory method, and thus, an adjudication method for reconciling differing results between experts is not applicable. The culture result is a definitive positive or negative.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
- No, a MRMC comparative effectiveness study was not explicitly done. This study assesses the performance of a diagnostic device (rapid test) against a gold standard (bacterial culture), not how human readers improve with or without AI assistance.
- The document does not mention any AI component or human-in-the-loop assistance in the context of improving human reader performance.
6. Standalone Performance Study
- Yes, a standalone study was done. The entire clinical performance section (Section 10.3) details the performance of the Wondfo One Step Strep A Swab Test as an algorithm/device only, without human-in-the-loop performance being a variable. The rapid test results were directly compared to the bacterial culture results.
7. Type of Ground Truth Used
- The primary ground truth used for the clinical study was bacterial culture.
- For the analytical performance studies (precision, cut-off, interference, specificity), the ground truth was established using known concentrations of inactivated Streptococcus pyogenes or other specified organisms/substances.
8. Sample Size for the Training Set
- The document does not provide information on a specific training set or its sample size. This is a rapid diagnostic test, not a machine learning algorithm that typically requires a distinct training phase. All listed performance characteristics studies (analytical and clinical) appear to be validation or test sets for the finished device.
9. How the Ground Truth for the Training Set Was Established
- As a training set is not explicitly mentioned for a machine learning model, the method for establishing its ground truth is not applicable in this context. The established ground truth for the analytical and clinical studies were bacterial culture and known concentrations of organisms/substances.
§ 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.