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The AccuProbe Group B Streptococcus Culture Identification Test is a rapid DNA probe test which utilizes the technique of nucleic acid hybridization for the identification of Group B Streptococcus isolated from culture.

The new indication for use covered in this 510(k) is for culture identification of Group B Streptococcus from vaginal and/or anorectal swab specimens collected from pregnant women at 35 to 37 weeks gestation, and cultured in Lim broth for 18 to 24 hours.

The ACCUPROBE Group B Streptococcus Culture Identification Test is a rapid DNA probe test which is based on the detection of ribosomal RNA sequences that are unique to Streptococcus agalactiae. Nucleic acid hybridization tests are based on the ability of complementary nucleic acid strands to specifically align and associate to form stable double-stranded complexes. The ACCUPROBE test uses a single-stranded DNA probe with a chemiluminescent label that is complementary to the ribosomal RNA of the target organism. After the ribosomal RNA is released from the organism, the labeled DNA probe combines with the target organism's ribosomal RNA to form a double-stranded DNA:RNA hybrid. The Selection reagent allows for the differentiation of non-hybridized and hybridized probe. The labeled DNA:RNA hybrids are measured in the Gen-Probe luminometer. A positive result is a luminometer reading equal to or greater than the cut-off. A value below this result is a negative result.

Here's a breakdown of the acceptance criteria and study details for the Gen-Probe ACCUPROBE Group B Streptococcus Culture Identification Test, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state quantitative acceptance criteria in terms of minimum sensitivity or specificity values that were required for approval. However, the performance data is presented against the "traditional culture methods" as the reference standard. The "Results Following Resolution of Discrepants" represent the final, most accurate performance after re-examination, and are therefore used for the reported device performance.

Note: The phrasing "substantially equivalent to other commercially available products" for the original device (and implicitly for this new indication) suggests that meeting performance levels comparable to predicate devices was the unstated acceptance criterion. The high sensitivity and specificity demonstrated are consistent with such an implicit criterion.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set:
  • Initial Determination Total: 1633 specimens (300 Pos/Pos + 18 Pos/Neg + 25 Neg/Pos + 1290 Neg/Neg)
  • Post-Resolution Total: 1633 specimens (316 Pos/Pos + 2 Pos/Neg + 8 Neg/Pos + 1307 Neg/Neg) - The total number of samples remains the same, only the classification changed after resolution.
• Data Provenance: The study was conducted across four clinical sites. The country of origin is not explicitly stated, but the submission is to the U.S. FDA, implying the data is likely from the United States. The study appears to be prospective in nature, as it involved developing a "clinical protocol" for specimen collection and processing, and tested against "traditional culture methods."

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

• Number of Experts: Not specified.
• Qualifications of Experts: Not specified.
  • The ground truth was established by "traditional culture methods" which included:
    • Culture on sheep blood agar and Lim broth
    • Subculture from Lim broth to sheep blood agar
    • Colony identification methods: CAMP test, PathoDx test, and the ACCUPROBE Group B Streptococcus test (this is confusing as the device itself is also listed as an identification method to establish ground truth, though it's likely referring to a conventional version or as confirmation).
  • While specific expert qualifications (e.g., "microbiologist with X years of experience") are not given, the reliance on established laboratory culture and identification techniques implies that trained laboratory personnel or microbiologists performed these tasks.

4. Adjudication Method for the Test Set

The study used an adjudication method for discrepant results.

• Method: "ACCUPROBE assays with discrepant results were repeated, and culture was either repeated from the swab pledget or re-examined to determine whether correct identification of Group B colonies had been made."
• This suggests a re-evaluation process for cases where the ACCUPROBE result did not match the initial culture result. It's a form of "resolution of discrepants" rather than a specific n-rater adjudication scheme (like 2+1, 3+1). The re-examination acted as the adjudicator.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

• No, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly described.
  • This study evaluated the standalone performance of the ACCUPROBE device compared to culture methods. It did not involve comparing human readers' performance with and without AI assistance. The device is an in-vitro diagnostic test, not an AI-assisted diagnostic tool for human interpretation.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

• Yes, a standalone performance study was done.
  • The ACCUPROBE Group B Streptococcus Culture Identification Test is a "rapid DNA probe test" that produces a "luminometer reading equal to or greater than the cut-off" for a positive result. This indicates an objective, automated reading by the Gen-Probe luminometer without human interpretation, making it a standalone device performance evaluation. The "Results Following Resolution of Discrepants" table clearly represents the standalone performance of the device against the established ground truth.

7. The Type of Ground Truth Used

• The ground truth used was expert consensus / established laboratory methods (culture and biochemical/immunological tests).
  • The "traditional culture methods" are considered the reference standard for identifying Group B Streptococcus from culture. These methods included sheep blood agar, Lim broth, CAMP test, and PathoDx test. The re-examination of discrepant results further refined this ground truth.

8. The Sample Size for the Training Set

• The document does not specify a separate training set or its sample size.
  • This type of DNA probe test is likely developed and optimized based on known genetic sequences and biochemical properties of the target organism (Streptococcus agalactiae) and non-target organisms. The document describes the "within run" and "between-run precision" studies, which are part of device characterization but not typically a "training set" in the machine learning sense. The clinical studies are presented as performance evaluation, not for training.

9. How the Ground Truth for the Training Set Was Established

• Since no separate "training set" is identified or discussed, the method for establishing its ground truth is not applicable based on the provided text.
  • The development of the probe itself would have relied on established scientific knowledge of Streptococcus agalactiae ribosomal RNA sequences, which would have been confirmed through molecular biology techniques and culture in a research and development phase prior to these clinical validation studies.

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