(485 days)
The BD MAX™ GBS Assay as implemented on the BD MAX™ System is a qualitative in vitro diagnostic test designed to detect Group B Streptococcus (GBS) DNA in Lim Broth cultures after incubation for greater than or equal to (>)18 hours, obtained from vaginal and rectal swab specimens from antepartum pregnant women. The test incorporates automated DNA extraction to isolate the target nucleic acid from the specimen and real-time polymerase chain reaction (PCR) to detect a 124 bp region of the cfb gene sequence of the Streptococcus agalactiae chromosome. Results from the BD MAX GBS Assay can be used as an aid in determining colonization status in antepartum women.
The BD MAX™ GBS Assay does not provide susceptibility results. Cultured isolates are necessary for performing susceptibility testing as recommended for penicillin-allergic women. Subculture to solid media for additional testing when indicated.
The BD MAX™ GBS Assay as implemented on the BD MAX™ System is a qualitative in vitro diagnostic test designed to detect Group B Streptococcus (GBS) DNA in Lim Broth cultures after incubation for greater than or equal to (>)18 hours, obtained from vaginal and rectal swab specimens from antepartum pregnant women. The test incorporates automated DNA extraction to isolate the target nucleic acid from the specimen and real-time polymerase chain reaction (PCR) to detect a 124 bp region of the cfb gene sequence of the Streptococcus agalactiae chromosome. Results from the BD MAX GBS Assay can be used as an aid in determining colonization status in antepartum women.
The BD MAX™ GBS Assay does not provide susceptibility results. Cultured isolates are necessary for performing susceptibility testing as recommended for penicillin-allergic women. Subculture to solid media for additional testing when indicated.
BD MAX™ GBS Assay Acceptance Criteria and Study Summary
1. Acceptance Criteria and Reported Device Performance
The provided document does not explicitly state pre-defined acceptance criteria for the clinical performance study. However, the study results, specifically the lower bounds of the 95% Confidence Intervals for Sensitivity and Specificity, are typically used to infer acceptable performance for diagnostic devices. Based on the "Total (95% CI)" row in Table 3:
| Metric | Implied Acceptance Criteria (based on 95% CI Lower Bound) | Reported Device Performance (Total) |
|---|---|---|
| Sensitivity | ≥ 90.0 % | 95.0 % (133/140) |
| Specificity | ≥ 94.7 % | 96.7 % (446/461) |
Note: The document only provides the overall sensitivity and specificity, not separate performance metrics for different GBS concentrations (e.g., moderate positive, low positive).
2. Sample Size and Data Provenance
- Test Set Sample Size: 601 compliant clinical specimens were included in the statistical analysis.
- Data Provenance:
- Country of Origin: United States. Specimens were collected and sent to laboratories at three separate metropolitan locations in the U.S.
- Retrospective or Prospective: Prospective investigational study.
3. Number of Experts and their Qualifications
The document does not explicitly state the number of experts used to establish the ground truth for the test set or their specific qualifications (e.g., radiologist with 10 years of experience). However, it implies that standard laboratory personnel, experienced in microbiology and culture-based diagnostics, would have performed the reference method. The "Clinical Performance" section mentions: "Swabs were sent for culture-based analysis to be performed by laboratories at three separate metropolitan locations in the U.S." and describes the steps involved in culture and identification.
4. Adjudication Method
The document does not describe a formal adjudication method for the test set results. The reference method (culture-based analysis) served as the direct comparator.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly mentioned or performed. This study focuses on the standalone performance of the BD MAX GBS Assay against a reference culture method, not on human reader improvement with or without AI assistance.
6. Standalone Performance (Algorithm Only)
Yes, a standalone performance study was done. The entire "Clinical Performance" section describes the performance of the BD MAX GBS Assay (the algorithm/device) compared to the reference culture method without human intervention in the result interpretation from the BD MAX system. The BD MAX™ GBS Assay streamlines and simplifies the testing process by eliminating the need for operator intervention from the time the sample is placed onto the BD MAX System until results are available.
7. Type of Ground Truth Used
The ground truth used was expert concensus (culture-based analysis) following CDC recommendations. This involved:
- Incubation of vaginal and rectal swab specimens in selective Lim Broth medium.
- Subculture to sheep blood agar plate and incubation.
- Gram staining and catalase production testing for GBS-suggestive colonies.
- Confirmatory methods: latex agglutination for beta-hemolytic GBS and CAMP reaction for gamma-hemolytic GBS.
8. Sample Size for the Training Set
The document does not specify a separate "training set" or its sample size. This type of diagnostic assay development typically involves initial analytical validation (e.g., LoD, precision, variants, specificity) using spiked or characterized samples, followed by clinical validation on independent patient samples. The information provided focuses on the clinical validation and analytical performance characteristics.
9. How the Ground Truth for the Training Set was Established
Given that a training set is not explicitly mentioned, the method for establishing its ground truth is also not detailed. However, for the analytical studies (e.g., Limit of Detection, Microbial Variants, Analytical Specificity), ground truth was established by:
- Using pooled clinical negative samples spiked with known concentrations of GBS culture.
- Testing specific GBS serotypes with known concentrations.
- Testing specific non-target organisms (viable organisms and genomic DNA) with known characteristics.
§ 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.