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IDI-Strep B™ assay is a qualitative in vitro diagnostic test for the rapid detection of Group B streptococcus (GBS) DNA in vaginal/rectal specimens from prepartum or intrapartum women. The test performed on the Smart Cycler® automated analyzer utilizes polymerase chain reaction (PCR) for the amplification of a cfb gene sequence of GBS recovered from clinical samples and fluorogenic target-specific hybridization for the detection of the amplified DNA.

IDI-Strep B™ assay can be used to establish GBS colonisation status of prepartum and intrapartum women.

IDI-Strep B™ assay is a qualitative in vitro diagnostic test for the rapid detection of Group B streptococcus (GBS) in vaginal/rectal specimens from intrapartum maternity patients. The test performed on the Smart Cycler® automated analyzer utilizes polymerase chain reaction (PCR) for the amplification of GBS DNA recovered from clinical samples and fluorogenic target-specific hybridization for the detection of the amplified GBS DNA.

IDI-Strep B™ assay can be used as the sole diagnostic information at the time of delivery for establishing GBS colonisation status of intrapartum maternity patients.

Test Description: GBS collected from a vaginal/rectal swab is resuspended in sample preparation buffer. A sample is added to the lysing tube containing glass beads. The proprietary procedure is based on a combination of chemical and physical (glass beads) action and takes less than 10 minutes. A sample of the lysate solution is then added to the tube containing the PCR master mix which has the GBS-specific primers used to amplify the GBS ofb gene, if present, and the internal control (IC) template. Finally, 25 µi is transferred to the reaction tube which is placed in the Smart Cycler® assay.

Amplified target DNA is detected with hybridization probes labeled with quenched fluorophores, i.e. molecular beacons. Different fluorophores are used for the GBS amplicon and for the detection of the IC amplicon. Their detection is independent of one another. Amplification of the internal control monitors for inhibitors potentially introduced with the clinical specimen and, in negative specimens, confirms the integrity of assay reagents. The interpretation of the data collected by the Smart Cycler® is made entirely by the diagnostic software of the Smart Cycler® instrument.

The amount of fluorescence at any given cycle, or following cycling, depends on the amount of specific amplicon present at that time. The Smart Cvcler® instrument monitors simultaneously the fluorescence emitted by each beacon, interprets all data and at the end of the cycling program provides a final result. The operation of the Smart Cycler® instrument is based on the proprietary microprocessor-controlled I-CORE® (Intelligent Cooling/Heating Optical Reaction) module. Each Smart Cycler® processing block contains 16 independently controlled, programmable I-Core® modules, each with one reaction site. Thermally optimized proprietary reaction tubes combined with the design of the I-CORE® modules allow very rapid temperature cycling and rapid amplification. Up to 6 Smart Cycler® processing blocks can be daisy-chained together, allowing simultaneous analysis of 96 discrete samples.

Here's an analysis of the provided text regarding the IDI-Strep B™ assay, addressing the requested information:

Acceptance Criteria and Device Performance Study for IDI-Strep B™ Assay

The IDI-Strep B™ assay is a qualitative in vitro diagnostic test for the rapid detection of Group B streptococcus (GBS) DNA in vaginal/rectal specimens from intrapartum maternity patients. Its performance was evaluated against a broth culture technique in a multi-center study.

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria. However, for diagnostic tests, performance metrics like sensitivity, specificity, and predictive values are typically assessed for substantial equivalence. The reported overall study results demonstrate the device's performance against the reference method.

Note: While specific "acceptance criteria" for these percentages are not explicitly listed, the FDA's decision to grant substantial equivalence implies that these results were deemed acceptable for the intended use and in comparison to the predicate device.

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

• Sample Size for Test Set: 803 vaginal/rectal swab specimens.
• Data Provenance: The study was a multi-center study with samples collected from intrapartum maternity patients. The locations of the investigational sites are mentioned as JGH, Montreal; MWH, Pittsburgh; ACH, Calgary; WCH, Milwaukee; and WHT, Houston. This indicates data from both Canada and the United States. The study was likely prospective, as samples were "collected from intrapartum maternity patients" and then evaluated.

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

The ground truth was established using a "broth culture technique." The document does not specify the number of experts involved in performing or interpreting the broth culture results, nor does it specify their qualifications. It simply refers to "broth culture" as the comparator method.

4. Adjudication Method for the Test Set

The document does not describe an explicit adjudication method for the test set. The comparison is made directly between the IDI-Strep B™ assay results and the broth culture results. Discrepancies were investigated post-hoc (e.g., initial culture negatives found to be positive upon investigation, retesting of invalid controls), but a formal, pre-defined adjudication process for conflicting results between the two methods is not detailed.

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

No, an MRMC comparative effectiveness study was not done. This study evaluates the performance of a diagnostic assay (IDI-Strep B™) compared to a laboratory reference method (broth culture) to detect the presence of GBS. It does not involve human readers interpreting images or data alongside and without AI assistance.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

The IDI-Strep B™ assay, being a PCR-based diagnostic test, inherently operates in a standalone mode (algorithm-only). The text states: "The interpretation of the data collected by the Smart Cycler® is made entirely by the diagnostic software of the Smart Cycler® instrument." This confirms that the device's performance is independent of human interpretation for the final result.

7. The Type of Ground Truth Used

The ground truth used was broth culture, which is a laboratory-based method for identifying and growing microorganisms. In this context, it serves as the reference standard for confirming the presence or absence of GBS.

8. The Sample Size for the Training Set

The document does not specify a separate training set size or methodology. The provided study describes the clinical validation of the device, implying that the 803 specimens were used as a test set against the reference standard. For a molecular diagnostic assay like this, "training" often refers to the internal development and optimization process, which is not typically detailed in 510(k) summaries in terms of distinct sample sizes. The Smart Cycler® software's interpretation is based on predefined algorithms rather than a machine learning model that would require an external training set from this specific clinical trial data.

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

As no specific "training set" is described in the context of this regulatory submission (which focuses on clinical validation), the ground truth establishment method for a training set is not applicable from the provided text. The device's internal algorithms would have been developed using known positive and negative controls and characterized samples during its engineering phase, but this is not the subject of this clinical performance study.

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