(57 days)
The Binax NOW™ Legionella Urinary Antigen Test is a rapid immunochromatographic assay for the qualitative detection of Legionella pneumophila serogroup 1 antigen (L. pneumophila serogroup 1 antigen) in human urine as an adjunct to culture for the presumptive diagnosis of Legionnaires' Disease. It is intended for in vitro diagnostic use.
The Binax NOW™ Legionella Urinary Antigen Test is an immunochromatographic membrane assay to detect Legionella pneumophila serogroup 1 antigen in human urine. A test strip, containing gold-conjugated and immobilized anti-Legionella pneumophila serogroup 1 antibodies, and a swab well are mounted on opposite sides of a cardboard, book-shaped hinged test device. A dacron swab is dipped into the urine to be tested and then inserted into the swab well. A single reagent is added to the swab well from a dropper bottle before closing the test device. Soluble antigen captured by immobilized anti-Legionella pneumophila serogroup 1 antibody reacts to bind the visualizing gold-conjugate. There are no transferring steps, the sample is contained, and results are available within 15 minutes.
Here's a breakdown of the acceptance criteria and study information for the Binax NOW™ Legionella Urinary Antigen Test, based on the provided text:
Acceptance Criteria and Reported Device Performance
| Criteria | Acceptance Threshold (Implicit) | Reported Device Performance (Binax NOW™) | Predicate Device Performance (Binax Legionella Urinary Antigen EIA) |
|---|---|---|---|
| Sensitivity | Not explicitly stated | 97% | 95% |
| Specificity | Not explicitly stated | 98% | 94% |
| Cross-Reactivity | Not explicitly stated | 98% specificity (against 200 non-Legionella pneumonia and UTI samples) | Not explicitly stated (compared against the same 200 samples) |
| Reproducibility | Not explicitly stated | 100% (360 samples correctly interpreted) | Not applicable (study performed on NOW™ test) |
| Quality Control | Not explicitly stated | 100% of 90 devices correctly interpreted (positive, negative, or invalid) | Not applicable (study performed on NOW™ test) |
Note: The acceptance thresholds are implicit as the submission focuses on demonstrating substantial equivalence to the predicate device. The performance of the NOW™ test is presented as being comparable or superior to the predicate device.
Study Details
2. Sample size used for the test set and the data provenance:
* Sample Size: 300 well-characterized frozen urine specimens were used for sensitivity and specificity determination. An additional 200 urine samples with other bacterial/fungal pneumonia or urinary tract infections were used for cross-reactivity testing. A separate 106 presumed negative urine specimens were also tested for specificity. For reproducibility, a panel of 360 coded specimens (negative, low, moderate, and high positive swabs) was used.
* Data Provenance: The specimens were "well characterized frozen urine specimens." The location of the main sensitivity and specificity testing was The University of Indiana. No country of origin is explicitly stated, but given the US submitter and testing location, it's highly likely to be US-based. The samples appear to be retrospective as they are "well characterized frozen urine specimens."
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
* The document does not specify the number of experts or their qualifications used to establish the ground truth. It states that "Specimens were considered true positives when the presence of infection was confirmed by culture, RIA, DFA or IFA." This implies reliance on established laboratory methods rather than direct expert consensus on each case.
4. Adjudication method for the test set:
* The document does not explicitly state an adjudication method (like 2+1 or 3+1). Ground truth was established by laboratory confirmation (culture, RIA, DFA, or IFA) for true positives. For reproducibility, it was a blind study where individuals from diverse educational backgrounds performed testing across different days. The correctness of interpretation refers to agreement with the known status of the coded specimens.
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:
* No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done, nor is there any mention of AI assistance. This device is an immunochromatographic assay, not an AI-powered diagnostic tool. The performance is for the device itself.
6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:
* Yes, this study represents a standalone performance evaluation of the Binax NOW™ Legionella Urinary Antigen Test. The test produces visually interpreted results, but the performance metrics (sensitivity, specificity) are based on the device's output compared to a "clinical diagnosis" (ground truth), not on a human interpreting the device's output and then being compared to another human or an AI. The reproducibility study directly assesses the device's consistency of output.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
* The ground truth for true positives was established by laboratory confirmation (culture, RIA, DFA or IFA) of Legionella pneumophila infection, coupled with a "Clinical Diagnosis." For other aspects like cross-reactivity and general specificity, it relied on "presumed negative" status or confirmation of other bacterial/fungal pneumonia or urinary tract infections.
8. The sample size for the training set:
* The document does not mention a training set. This is a point-of-care immunoassay, not a machine learning model, so the concept of a training set as used in AI/ML is not applicable here.
9. How the ground truth for the training set was established:
* Not applicable, as there is no training set mentioned for this type of device.
§ 866.3300
Haemophilus spp. serological reagents.(a)
Identification. Haemophilus spp. serological reagents are devices that consist of antigens and antisera, including antisera conjugated with a fluorescent dye, that are used in serological tests to identifyHaemophilus spp. directly from clinical specimens or tissue culture isolates derived from clinical specimens. The identification aids in the diagnosis of diseases caused by bacteria belonging to the genusHaemophilus and provides epidemiological information on diseases cause by these microorganisms. Diseases most often caused byHaemophilus spp. include pneumonia, pharyngitis, sinusitis, vaginitis, chancroid venereal disease, and a contagious form of conjunctivitis (inflammation of eyelid membranes).(b)
Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to § 866.9.