(77 days)
The QuantStudio™ Dx Real-Time PCR Instrument with QuantStudio™ Dx Software is intended to perform fluorescence-based PCR to provide detection of FDA cleared and approved nucleic acid sequences in human-derived specimens. The QuantStudio™ Dx Real-Time PCR Instrument with QuantStudio™ Dx Software is intended for in vitro diagnostic use by trained laboratory technologists in combination with nucleic acid reagent kits/tests manufactured and labeled for diagnostic purposes on this instrument.
The QuantStudio™ Dx Real-Time PCR Instrument is a bench top Real-Time PCR instrument that uses fluorescent-based polymerase chain reaction (PCR) reagents to provide qualitative or quantitative detection of target nucleic acid sequences (targets) using real-time analysis.
The QuantStudio™ Dx Real-Time PCR Instrument system includes the following components:
- QuantStudio™ Dx Real-Time PCR instrument with embedded graphical user . interface (eGUI) Touchscreen
- Thermal Block, also referred to as the sample block, with associated Heated Cover . and Plate Adaptor
- Calibration and verification materials for instrument qualification .
- . Computer workstation with a monitor, keyboard and mouse
- QuantStudio™ Dx instrument software .
Here's an analysis of the provided text to extract information about the acceptance criteria and the study demonstrating the device meets them:
K123955: QuantStudio™ Dx Real-Time PCR Instrument
This submission concerns the QuantStudio™ Dx Real-Time PCR Instrument, which is a benchtop real-time PCR instrument intended for in vitro diagnostic use to detect FDA-cleared and approved nucleic acid sequences in human-derived specimens. The performance data presented focuses on its use with the Quidel® Molecular Real-Time PCR Direct C. difficile Tox A/B Assay.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are implicitly derived from the "Precision/Reproducibility" and "Detection Limit" sections, and then more explicitly in the "Comparison Studies" section through performance metrics like sensitivity and specificity against a reference method (Tissue Culture Cytotoxicity Assay and Enhanced Toxigenic Culture).
Implicit Acceptance Criteria (Analytical Performance):
| Performance Metric | Acceptance Criteria (Implicit) | Reported Device Performance (QuantStudio™ Dx with Quidel C. difficile Assay) |
|---|---|---|
| Precision (Within-Lab Repeatability) | Consistent detection rates across different LoD levels and operators; low %CV for Ct values. (Generally, 100% detection for 2X LoD and above, and high detection for 0.3X LoD) | 5X LoD: 100% Detection, Avg Ct: 16.51, STDEV: 0.42, %CV: 2.6% |
| 2X LoD: 100% Detection, Avg Ct: 17.70, STDEV: 0.76, %CV: 4.3% | ||
| 0.3X LoD: 88% Detection, Avg Ct: 21.13, STDEV: 1.37, %CV: 6.5% | ||
| Negative: 0% Detection | ||
| Reproducibility (Multi-Site) | Consistent detection rates and low %CV for Ct values across multiple sites, operators, and days. (Generally, 100% detection for 2X LoD and above, and high detection for 0.3X LoD) | High Negative 0.3x LoD: 38/90 positive across 3 sites (individual site results: 8/30, 15/30, 15/30); AVE Ct %CV range: 1.3-5.0 |
| Low Positive 2x LoD: 90/90 positive across 3 sites; AVE Ct %CV range: 0.8-5.9 | ||
| Med Positive 5x LoD: 90/90 positive across 3 sites; AVE Ct %CV range: 0.4-4.2 | ||
| Negative Specimen: 0/90 positive | ||
| Negative Control: 0/90 positive | ||
| Positive Control: 90/90 positive; AVE Ct %CV range: 0.1-0.6 | ||
| Detection Limit (LoD) | Defined as the lowest concentration at which 95% of all replicates tested positive. | Final assay LoD: 4.2E-01 CFU/assay (based on ATCC BAA-1870 and ATCC BAA-1872 strains, where 95% positivity was observed) |
Explicit Acceptance Criteria (Clinical Performance against Reference Method):
| Performance Metric | Acceptance Criteria (Implicit - based on comparison study to predicate/reference) | Reported Device Performance (QuantStudio™ Dx with Quidel C. difficile Assay) |
|---|---|---|
| Sensitivity (vs. Tissue Culture Cytotoxicity Assay) | High sensitivity (specific numerical target not provided, but typically >90% for diagnostic assays) | 93.3% (95% CI: 86.9% - 96.7%) |
| Specificity (vs. Tissue Culture Cytotoxicity Assay) | High specificity (specific numerical target not provided, but typically >90% for diagnostic assays) | 93.4% (95% CI: 91.3% - 95.0%) |
| Sensitivity (vs. Enhanced Toxigenic Culture) | High sensitivity | 87.3% (95% CI: 81.1% - 91.6%) |
| Specificity (vs. Enhanced Toxigenic Culture) | High specificity | 98.7% (95% CI: 97.5% - 99.4%) |
2. Sample Size and Data Provenance for the Test Set
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Analytical Test Set (Precision/Reproducibility):
- Precision: A "blinded four-member panel consisting of C. difficile positive and negative sample" tested over 12 days by 2 operators, twice a day, using a single assay lot. The total number of tests for each panel member would be 48 (2 operators * 2 times/day * 12 days). For example, 0.3x LoD shows 88% detection, implying 42 positive results out of 48 total tests.
- Reproducibility: A "blinded and randomized study panel" tested at three (3) test sites. Each site tested the panel for five (5) days in triplicate on each instrument, by two operators. Each operator ran the panel once a day. This means for each panel member, at each site, there were 30 tests (2 operators * 5 days * 3 replicates). Total tests for each panel member across all three sites would be 90 (30 tests/site * 3 sites).
- Data Provenance: Not explicitly stated for analytical studies, but given the manufacturer's location and the mention of Quidel, it's likely primarily US-based or an international corporate R&D setting. The study is prospective in nature, designed specifically for this validation.
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Clinical Test Set (Comparison Studies):
- Sample Size: 792 samples initially collected. 788 specimens were used for the Tissue Culture Cytotoxicity Assay comparison, and 791 specimens were used for the Enhanced Toxigenic Culture comparison (due to removed invalid/indeterminate results).
- Data Provenance: Prospective study conducted from August to November 2012. Samples were "collected from patients suspected of having Clostridium difficile-associated disease (CDAD) at four (4) distinct geographical sites across the United States."
3. Number of Experts and Qualifications for Ground Truth
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Analytical Studies: Ground truth for analytical studies (precision, reproducibility, LoD) is typically based on known concentrations of the target analyte (like C. difficile strains in CFU/mL) prepared in a laboratory setting. No external "experts" are typically involved in establishing this ground truth beyond the scientific personnel designing and executing the standard preparations and dilutions.
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Clinical Studies:
- Tissue Culture Cytotoxicity Assay: This is a laboratory-based reference method for detecting C. difficile toxin. The "experts" involved would be the laboratory personnel performing and interpreting this gold standard assay. Their qualifications are not specified but would typically involve trained medical technologists or microbiologists.
- Enhanced Toxigenic Culture: This is another laboratory-based reference method. Similar to the cytotoxicity assay, the "experts" would be trained laboratory personnel. Their qualifications are not specified.
- The document does not mention a panel of experts for consensus reading of raw data or images. The ground truth relies on established laboratory methodologies.
4. Adjudication Method for the Test Set
The document does not describe an adjudication method involving multiple human readers for the test set.
- For the analytical studies, results are based on direct output from the instrument (detection yes/no, Ct values) against predetermined concentrations, so no adjudication is required.
- For the clinical comparison studies, the "ground truth" (reference standard) is provided by the Tissue Culture Cytotoxicity Assay and Enhanced Toxigenic Culture. Discordant results between the Quidel Molecular Direct C. difficile Assay on the QuantStudio™ Dx and these reference methods were further investigated by testing with an "FDA-cleared molecular device." This serves as a form of secondary adjudication or reconciliation for discordant results but does not involve human readers adjudicating an algorithm's output. For example:
- For the Cytotoxicity comparison, 45 Quidel Positive/Tissue Culture Negative were re-tested with an FDA-cleared molecular device: 35 positive, 9 negative.
- 7 Quidel Negative/Tissue Culture Positive were re-tested with an FDA-cleared molecular device: 2 positive, 5 negative.
- Similar reconciliation was done for the Enhanced Toxigenic Culture comparison.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This study focuses on the standalone performance of the instrument with a specific diagnostic assay, and its concordance with established reference laboratory methods. There is no mention of human readers evaluating cases with and without AI assistance.
6. Standalone (Algorithm Only) Performance
Yes, the studies presented demonstrate standalone performance of the QuantStudio™ Dx Real-Time PCR Instrument (in conjunction with the Quidel Molecular Direct C. difficile Assay). The data provided (detection rates, Ct values, sensitivity, specificity) represent the performance of the instrument/assay system without direct human-in-the-loop intervention for result interpretation beyond running the assay and reviewing its output.
7. Type of Ground Truth Used
- Analytical Studies (Precision, Reproducibility, LoD): Known concentrations of specific C. difficile strains (e.g., ATCC BAA-1870 and ATCC BAA-1872) diluted in a negative fecal matrix. This is a form of analytical (spiked) ground truth.
- Clinical Studies (Comparison Studies):
- Tissue Culture Cytotoxicity Assay: An established laboratory method for detecting C. difficile toxin.
- Enhanced Toxigenic Culture: An established laboratory method for detecting toxigenic C. difficile.
- For discordant results, an "FDA-cleared molecular device" was used for reconciliation.
These are all forms of reference standard (laboratory-based) ground truth.
8. Sample Size for the Training Set
The document does not provide information on a training set sample size. The submission describes the performance validation of the instrument when used with a specific diagnostic assay, rather than the development and training of a machine learning algorithm. PCR instruments perform predefined biochemical reactions and detect fluorescence signals based on set parameters, they do not typically undergo "training" in the machine learning sense.
9. How the Ground Truth for the Training Set was Established
Since there is no mention of a training set for a machine learning algorithm, there is no information provided on how ground truth was established for a training set. The instrument's operation is based on established PCR principles and specified assay parameters.
§ 862.2570 Instrumentation for clinical multiplex test systems.
(a)
Identification. Instrumentation for clinical multiplex test systems is a device intended to measure and sort multiple signals generated by an assay from a clinical sample. This instrumentation is used with a specific assay to measure multiple similar analytes that establish a single indicator to aid in diagnosis. Such instrumentation may be compatible with more than one specific assay. The device includes a signal reader unit, and may also integrate reagent handling, hybridization, washing, dedicated instrument control, and other hardware components, as well as raw data storage mechanisms, data acquisition software, and software to process detected signals.(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 the limitations in § 862.9. The special control is FDA's guidance document entitled “Class II Special Controls Guidance Document: Instrumentation for Clinical Multiplex Test Systems.” See § 862.1(d) for the availability of this guidance document.