(90 days)
The DiaSorin Molecular Simplexa™ HSV 1 & 2 Direct assay is intended for use on the LIAISON® MDX instrument for the qualitative detection and differentiation of herpes simplex virus (HSV-2) DNA present in mucocutaneous and cutaneous lesion swabs from patients with signs and symptoms of HSV-1 or HSV-2 infection. This test is an aid in the differential diagnosis of HSV-1 and HSV-2 infections.
The assay is not intended for use as a screening test for the presence of HSV-2 in blood or blood products. The assay is for professional use only.
Simplexa™ HSV 1 & 2 Positive Control Pack MOL2160
The Simplexa™ HSV 1 & 2 Positive Control Pack is intended to be used as a control with the Simplexa™HSV 1 & 2 Direct kit.
This control is not intended for use with other assays or systems.
The Simplexa™ HSV 1 & 2 Direct assay system is a real-time PCR that enables the direct amplification, detection and differentiation of HSV-1 and/or HSV-2 DNA from unprocessed cutaneous and mucocutaneous lesion swab specimens without nucleic acid extraction. The system consists of the Simplexa™ HSV 1 & 2 Direct assay, the LIAISON® MDX (with LIAISON® MDX Studio Software), the Direct Amplification Disc and associated accessories.
In the Simplexa™ HSV 1 & 2 Direct assay, bi-functional fluorescent probe-primers are used together with corresponding reverse primers to amplify HSV-1, HSV-2 and internal control targets. Well conserved regions of the HSV-1 and HSV-2 DNA polymerase genes are targeted to identify HSV-1 and HSV-2 DNA respectively in the specimen. An internal control is used to detect PCR failure and/or inhibition.
Here's a breakdown of the acceptance criteria and study information for the Simplexa™ HSV 1 & 2 Direct device, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state pre-defined acceptance criteria (e.g., "PPA must be ≥ 95%"). Instead, it presents the "Clinical Agreement" results from validation studies and implies that these figures demonstrate acceptable performance for clearance. Therefore, the "acceptance criteria" listed below are inferred from the reported performance, representing the observed outcomes deemed sufficient for the device to be considered substantially equivalent.
| Metric (Target) | Acceptance Criteria (Implied from Performance) | HSV-1 Cutaneous Swabs Reported Performance | HSV-1 Mucocutaneous Swabs Reported Performance | HSV-2 Cutaneous Swabs Reported Performance | HSV-2 Mucocutaneous Swabs Reported Performance |
|---|---|---|---|---|---|
| Positive Percent Agreement (PPA) - Prospective | N/A (Observed: 97.0% - 100.0%) | 100.0% (30/30) | |||
| (95% CI: 88.7%-100.0%) | 98.2% (162/165) | ||||
| (95% CI: 94.4%-99.6%) | 97.0% (32/33) | ||||
| (95% CI: 84.4%-99.5%) | 99.5% (193/194) | ||||
| (95% CI: 97.1%-100.0%) | |||||
| Negative Percent Agreement (NPA) - Prospective | N/A (Observed: 96.3% - 97.9%) | 96.3% (182/189) | |||
| (95% CI: 92.6%-98.5%) | 97.5% (703/721) | ||||
| (95% CI: 96.1%-98.4%) | 97.9% (182/186) | ||||
| (95% CI: 94.6%-99.2%) | 96.7% (669/692) | ||||
| (95% CI: 95.1%-97.8%) | |||||
| Positive Percent Agreement (PPA) - Retrospective | N/A (Observed: 100.0%) | 100.0% (26/26) | |||
| (95% CI: 87.1%-100.0%) | 100.0% (32/32) | ||||
| (95% CI: 89.3%-100.0%) | 100.0% (29/29) | ||||
| (95% CI: 88.3%-100.0%) | 100.0% (22/22) | ||||
| (95% CI: 85.1%-100.0%) | |||||
| Negative Percent Agreement (NPA) - Retrospective | N/A (Observed: 98.9% - 100.0%) | 98.9% (91/92) | |||
| (95% CI: 94.1%-99.8%) | 99.1% (113/114) | ||||
| (95% CI: 95.2%-100.0%) | 100.0% (89/89) | ||||
| (95% CI: 95.9%-100.0%) | 100.0% (124/124) | ||||
| (95% CI: 97.0%-100.0%) |
Note on "Acceptance Criteria": The document provides the study results directly. For diagnostics, these agreement percentages are typically compared against pre-specified acceptance criteria. The absence of explicit acceptance criteria in the provided text implies that the reported performance was considered adequate for FDA clearance.
2. Sample Size Used for the Test Set and Data Provenance
- Prospective Study 1 (K150962 data, re-used):
- Original Collected: 718 samples
- Evaluated: 696 samples (after removals for various reasons like not tested, invalid results, internal control failure, wrong sample type, insufficient volume, control issues, non-enrollable)
- Data Provenance: From 6 geographically diverse locations, prospectively collected from May 28, 2014, through December 4, 2014.
- Prospective Study 2 (K173798 data):
- Original Collected: 514 samples
- Evaluated:
- 511 samples for Simplexa™ HSV 1 & 2 Direct
- 512 samples for culture method
- 510 samples for bi-directional sequencing method (after removals for EC505 codes, insufficient volume, daily control issues, non-enrollable)
- Data Provenance: From 4 geographically diverse sites, prospectively collected from July 24, 2017, through October 11, 2017.
- Retrospective Study:
- Evaluated: 174 Cutaneous HSV-1 swabs, 174 Mucocutaneous HSV-2 swabs, and 17 samples from unknown locations.
- Data Provenance: Retrospectively collected from June 6, 2011, to May 17, 2014, and February 21, 2017, through July 17, 2017.
All clinical samples were cutaneous and mucocutaneous lesion swabs from patients with signs and symptoms of HSV-1 or HSV-2 infection.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not specify the number or qualifications of experts for establishing ground truth. The ground truth was established using a "composite comparator algorithm" rather than expert opinion alone.
4. Adjudication Method for the Test Set
The ground truth was established using a composite comparator algorithm based on a "2 out of 3 rule":
- Components: Culture, bi-directional sequencing, and an FDA-cleared NAAT (Nucleic Acid Amplification Test).
- Method: Any sample yielding a positive result by either sequencing or culture was then tested on an FDA-cleared NAAT. A "2 out of 3 rule" (implying agreement between at least two of the three methods) was used to determine the final composite results.
- Note: For culture, HSV-2 was tested first. If positive for HSV-2, no further culture testing was done (meaning dual positives could not be identified by culture alone).
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No, an MRMC comparative effectiveness study was not explicitly done. The study focuses on evaluating the device's performance against a composite reference method, not on human reader performance with or without AI assistance. The device is a molecular diagnostic assay, not an AI-assisted diagnostic tool for human readers.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the studies presented are for the standalone performance of the Simplexa™ HSV 1 & 2 Direct assay, which is a real-time PCR system. This system performs direct amplification, detection, and differentiation of HSV-1 and HSV-2 DNA from unprocessed swab specimens, without requiring human interpretation of results beyond reading the instrument's output. The "algorithm" here refers to the PCR assay's mechanics and the LIAISON® MDX instrument's software for detection.
7. The Type of Ground Truth Used
The ground truth for the clinical studies was a composite comparator algorithm consisting of:
- Cell culture
- Bi-directional sequencing
- An FDA-cleared NAAT
This is considered a robust method for establishing ground truth in molecular diagnostics, combining phenotypic (culture) and genotypic (sequencing, NAAT) evidence.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of machine learning, as this is a molecular diagnostic assay cleared through substantial equivalence, not an AI/ML-based device requiring separate training and test sets in that sense. The analytical studies (reproducibility, LoD, cross-reactivity, interference) use contrived samples and defined panels. The "clinical agreement" uses the prospective and retrospective patient samples as the validation/test sets to demonstrate performance against the composite reference standard.
9. How the Ground Truth for the Training Set Was Established
As stated above, no "training set" in the AI/ML context is described. For the analytical studies, the "ground truth" (e.g., presence/absence and concentration of a virus, presence of cross-reactants/interferents) was established by using:
- Quantified stocks of HSV-1 and HSV-2 (for Limit of Detection, Analytical Reactivity).
- Known concentrations of various microorganisms and substances (for Cross-Reactivity and Interference studies).
- Contrived sample pools with known viral loads (for Reproducibility and Competitive Interference).
§ 866.3309 Herpes virus nucleic acid-based cutaneous and mucocutaneous lesion panel.
(a)
Identification. A herpes virus nucleic acid-based cutaneous and mucocutaneous lesion panel is a qualitative in vitro diagnostic device intended for the simultaneous detection and differentiation of different herpes viruses in cutaneous and mucocutaneous lesion samples from symptomatic patients suspected of Herpetic infections. Negative results do not preclude infection and should not be used as the sole basis for treatment or other patient management decisions. The assay is not intended for use in cerebrospinal fluid samples.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Premarket notification submissions must include detailed documentation for the device description, including the device components, ancillary reagents required but not provided, and a detailed explanation of the methodology including primer design and selection.
(2) Premarket notification submissions must include detailed documentation from the following analytical and clinical performance studies: Analytical sensitivity (Limit of Detection), reactivity, inclusivity, precision, reproducibility, interference, cross reactivity, carry-over, and cross contamination.
(3) Premarket notification submissions must include detailed documentation of a clinical study using lesion samples in which Herpes Simplex Virus 1, Herpes Simplex Virus 2, or Varicella Zoster Virus DNA detection was requested. The study must compare the device performance to an appropriate well established reference method.
(4) A detailed explanation of the interpretation of results and acceptance criteria must be included in the device's 21 CFR 809.10(b)(9) compliant labeling.
(5) The device labeling must include a limitation statement that reads: “The device is not intended for use with cerebrospinal fluid or to aid in the diagnosis of HSV or VZV infections of the central nervous system (CNS).”
(6) Premarket notification submissions must include quality assurance protocols and a detailed documentation for device software, including, but not limited to, standalone software applications and hardware-based devices that incorporate software.
(7) The risk management activities performed as part of the manufacturer's 21 CFR 820.30 design controls must document an appropriate end user device training program that will be offered as part of efforts to mitigate the risk of failure to correctly operate the instrument.