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The Solana® GBS assay is a qualitative in vitro diagnostic test for detection of Group B Streptococcus in either LIM or Carrot enrichment broth cultures of vaginal/rectal swabs from antepartum women following 18 to 24 hours of incubation. The Solana® GBS Assay utilizes helicase-dependent amplification (HDA) of the Thiolase (atoB) gene sequence. The Solana® GBS Assay is intended for use only with the Solana® Instrument.

The Solana® GBS Assay does not provide susceptibility results. Culture isolates are needed for performing susceptibility testing as recommended for penicillin-allergic women.

The Solana GBS Assay amplifies and detects GBS DNA isolated from enrichment broth cultures of vaginal/rectal swabs from antepartum women following 18 to 24 hours of incubation.

The assay consists of two (2) major steps: 1) specimen preparation, and 2) amplification and detection of target sequence specific to GBS using isothermal Helicase-Dependent Amplification (HDA) in the presence of target-specific fluorescence probe.

Patient specimen is transferred to a Process Buffer tube, subjected to heat treatment at 95 ± 2°C for 5 minutes and mixed. The processed sample is transferred to a Reaction Tube and mixed. The Reaction Tube contains lyophilized HDA reagents, dNTPs, primers and probes. Once rehydrated with the processed sample, the Reaction Tube is placed in Solana for amplification and detection of specific target sequences. In Solana, the GBS target sequence is amplified by GBS specific primers and detected by a GBS specific fluorescence probe included in the Reaction Tube. A competitive process control (PRC) is included in the Process Tube to monitor sample processing, for the presence of inhibitory substances in clinical samples, reagent or device failure. The PRC target is amplified by specific primers and detected by a PRC specific fluorescence probe.

The target and PRC probes are labeled with a quencher on one end and a fluorophore (FAM or ROX, respectively) on the other end. In addition, the target and PRC probes carry a ribonucleic acid. Upon annealing to GBS or PRC amplicons, the fluorescence probes are cleaved by RNaseH2 and the fluorescence signal increases due to physical separation of fluorophore from quencher. Solana measures and interprets the fluorescent signal, using on-board method-specific algorithms. Solana will then report the test results to the user on its display screen, and it can print out the results using the attached printer.

Here's a breakdown of the acceptance criteria and study details for the Solana GBS Assay, based on the provided text:

Acceptance Criteria and Device Performance

The provided document defines the analytical and clinical performance characteristics of the Solana GBS Assay. While explicit "acceptance criteria" are not presented as a direct table of pass/fail thresholds before the study, the "Comparison with predicate" section (Table 4) and the "Clinical studies" section (Table 13) present the performance of the predicate device and the new device, respectively. The implication is that the new device's performance needs to be comparable or superior to the predicate for substantial equivalence.

Here's a table summarizing the reported device performance, with the predicate performance included for comparison where available:

Table: Acceptance Criteria (Implied) and Reported Device Performance

Study Details

1. Sample Size Used for the Test Set and Data Provenance:

   • Test Set Sample Size: 753 specimens were collected for the clinical study. One specimen was invalid, resulting in 752 specimens analyzed.
     • 403 specimens used LIM broth.
     • 350 specimens used Carrot broth.
   • Data Provenance: Prospective study. Specimens were collected from four distinct geographical sites across the United States.

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

   • The document states that specimens were tested by "bacterial culture" to establish ground truth.
   • The specific number of experts and their qualifications (e.g., radiologist with 10 years of experience) are not specified in the provided text. The ground truth for this in vitro diagnostic device is standard laboratory bacterial culture, which is typically considered the gold standard for GBS detection. Expert adjudication as would be seen in an imaging study is not applicable here.

3. Adjudication Method for the Test Set:

   • Not applicable in the context of this in vitro diagnostic bacterial culture-based study. The ground truth was established by bacterial culture. For samples where the Solana GBS Assay was positive but bacterial culture was negative (False Positives), these were further tested by "an additional FDA-cleared molecular test" (19 of 23 instances were confirmed positive by this molecular test). This serves as a form of adjudication or further investigation for discordant results.

4. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done:

   • No, an MRMC comparative effectiveness study was not done. This type of study is typically performed for AI-assisted diagnostic tools that involve human interpretation (e.g., radiologists reading images with AI-aid). The Solana GBS Assay is an automated in vitro diagnostic device, not an AI assistance tool for human readers.

5. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done:

   • Yes, the primary performance evaluation (clinical study) is a standalone performance assessment of the Solana GBS Assay compared to bacterial culture. The device "measures and interprets the fluorescent signal, using on-board method-specific algorithms" and "then reports the test results to the user on its display screen." There is no human interpretation component in the device's determination of positive/negative results.

6. The Type of Ground Truth Used:

   • Bacterial Culture was used as the primary ground truth for clinical sensitivity and specificity.
   • For discordant results (Solana Positive/Culture Negative), an additional FDA-cleared molecular test was used to further confirm positive status.

7. The Sample Size for the Training Set:

   • The document does not explicitly state the sample size used for the training set. The performance characteristics listed (LOD, reproducibility, analytical specificity, clinical performance) are derived from the validation studies of the device. For in vitro diagnostic molecular assays like this, the "training" (development) of the assay's parameters (e.g., primer design, probe chemistry, HDA conditions, detection algorithms) is an internal process, but the specific datasets used for that initial development are not typically disclosed in a 510(k) summary for these types of devices. The clinical and analytical studies described serve as the test set for regulatory submission.

8. How the Ground Truth for the Training Set was Established:

   • As the training set size is not explicitly mentioned, the method for establishing its ground truth is also not described in the document. However, for developing such assays, ground truth for training would typically involve well-characterized bacterial cultures (known positive and negative strains at various concentrations) and potentially clinical samples with established culture results, similar to how the ground truth for the validation test set was established.

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