(160 days)
Light Diagnostics SimulFluor® HSV1/2 Immunofluorescence Assay is a direct immunofluorescence test intended for the detection and identification of herpes simplex virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2) following amplification in cell culture or by direct examination of clinical specimens prepared by cytocentrifugation. Specimens found to be negative on direct specimen examination should be tested by cell culture.
For in vitro diagnostic use.
Light Diagnostics SimulFluor® HSV 1/2 Immunofluorescence Assay utilizes a single reagent for the simultaneous detection and identification of HSV-1 and HSV-2. The SimulFluor® HSV 1/2 Reagent consists of two components; the primary component specific for HSV-1 will bind to the glycoprotein C and a capsid-associated protein in HSV-1 infected cells, while the secondary component, specific for HSV-2, will bind to the glycoprotein G in HSV-2 infected cells. Unbound reagent is removed by rinsing with phosphate-buffered saline (PBS). Illumination with ultraviolet light allows visualization of the antigenantibody complexes by fluorescence microscopy. When an FITC filter set is used, HSV-1- infected cells will exhibit apple-green fluorescence and HSV-2infected cells will exhibit yellow-gold fluorescence. The uninfected cells will stain a dull red due to the presence of Evans blue in the SimulFluor® HSV 1/2 reagent.
A blend of monoclonal antibodies directed against HSV-1 and HSV-2 is used in the Light Diagnostics SimulFluor® HSV 1/2 reagent. The use of monoclonal antibodies ensures increased specificity of reagent and reduces the risk of nonspecific background or interference.
This document describes the acceptance criteria and study details for the Light Diagnostics SimulFluor® HSV1/2 Immunofluorescence Assay.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are implied by the comparison to predicate devices and the confidence intervals reported for sensitivity, specificity, and percent agreement, indicating that the device's performance should be comparable to or ideally exceed these established methods. The "Clinical Study: Site 1" and "Clinical Study: Site 2" sections provide the reported device performance. Given the type of device (an immunofluorescence assay comparing to similar assays), the primary performance metrics are sensitivity, specificity, and percent agreement.
| Performance Metric | Acceptance Criteria (Implied) | Reported Device Performance (Site 1 - Direct Specimen vs. Culture) | Reported Device Performance (Site 1 - vs. Comparative Device) | Reported Device Performance (Site 2 - Shell Vials vs. Comparative Device) | Reported Device Performance (Site 2 - Culture Plates vs. Comparative Device) |
|---|---|---|---|---|---|
| HSV-1 Detection | High sensitivity, specificity, and agreement compared to predicate. | Sensitivity: 89.5% (17/19), Specificity: 100% (128/128), Agreement: 98.6% | Percent Agreement: 100% | Percent Agreement: 96% | Percent Agreement: 100% |
| HSV-2 Detection | High sensitivity, specificity, and agreement compared to predicate. | Sensitivity: 92.6% (25/27), Specificity: 100% (120/120), Agreement: 98.6% | Percent Agreement: 100% | Percent Agreement: 100% | Percent Agreement: 100% |
Note on Acceptance Criteria: The document does not explicitly state numerical acceptance criteria in a dedicated section. Instead, the "Conclusions drawn from evaluations" section states that the device's performance characteristics "were shown to be substantially equivalent to those of Bartels HSV Typing Test and the DPC PathoDx® Herpes Typing kit." Therefore, the reported performance metrics (sensitivity, specificity, and percent agreement with tight confidence intervals) meeting or exceeding those of the predicate devices are the implicit acceptance criteria.
2. Sample Size Used for the Test Set and Data Provenance
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Clinical Study: Site 1
- Test Set Sample Size: 191 specimens were submitted. After exclusions (40 insufficient cells, 1 contaminated culture, 3 VZV positive), the evaluable sample size for direct specimen testing was 147 (19+128 for HSV-1, 27+120 for HSV-2). For comparison against a comparative device, 33 HSV-1 and 29 HSV-2 isolates were identified by both reagents.
- Data Provenance: North-central United States, retrospective (specimens "were submitted" indicating existing samples).
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Clinical Study: Site 2
- Test Set Sample Size:
- Shell vials: 214 specimens. 24 HSV-1 and 37 HSV-2 isolates were detected.
- Culture plates: 227 specimens. 32 HSV-1 and 46 HSV-2 isolates were detected.
- Data Provenance: Southwestern United States, retrospective (specimens "were submitted" indicating existing samples).
- Test Set Sample Size:
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 used to establish the ground truth. It refers to "clinical virology laboratory" and "reference laboratory" and implies standard laboratory procedures for culture confirmation.
4. Adjudication Method for the Test Set
The document does not describe an adjudication method for reconciling disagreements. For Site 1, the "culture confirmation" was used as the reference against which the direct specimen testing was compared. For the comparison against predicate devices, it appears a straightforward comparison of results was performed.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve With AI vs Without AI Assistance
This section is not applicable as the described device is an immunofluorescence assay for detecting viruses, not an AI-assisted diagnostic tool interpreted by human readers. It's a laboratory test where a technician observes fluorescence, not a system that improves human diagnostic performance via AI.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
This section is not applicable. The device is an immunofluorescence assay that requires manual preparation, staining, and microscopic observation by a trained laboratory technician. It is not an automated algorithm.
7. The Type of Ground Truth Used (Expert Consensus, Pathology, Outcomes Data, etc.)
The ground truth used was cell culture (viral culture), which is a gold standard for detecting and identifying HSV-1 and HSV-2. In Site 1, "culture confirmation" was used. In Site 2, "standard cultures" and "spin-amplified shell vials" were used as reference methods.
8. The Sample Size for the Training Set
The document does not explicitly describe a separate "training set" for the clinical evaluation. The non-clinical evaluation section mentions that antibodies were "characterized for their ability to detect HSV types 1 and 2" using "reference viral strains and clinical isolates," but this is more akin to initial assay development and validation rather than a distinct training set for an algorithm.
9. How the Ground Truth for the Training Set Was Established
Given the absence of an explicit "training set" as understood for machine learning algorithms, this question is not applicable in the context of this immunofluorescence assay submission. The "characterization" of the antibodies relied on testing with "reference viral strains and clinical isolates" whose identities would have been established through standard virological methods.
§ 866.3305 Herpes simplex virus serological assays.
(a)
Identification. Herpes simplex virus serological assays are devices that consist of antigens and antisera used in various serological tests to identify antibodies to herpes simplex virus in serum. Additionally, some of the assays consist of herpes simplex virus antisera conjugated with a fluorescent dye (immunofluorescent assays) used to identify herpes simplex virus directly from clinical specimens or tissue culture isolates derived from clinical specimens. The identification aids in the diagnosis of diseases caused by herpes simplex viruses and provides epidemiological information on these diseases. Herpes simplex viral infections range from common and mild lesions of the skin and mucous membranes to a severe form of encephalitis (inflammation of the brain). Neonatal herpes virus infections range from a mild infection to a severe generalized disease with a fatal outcome.(b)
Classification. Class II (special controls). The device is classified as class II (special controls). The special control for the device is FDA's revised guidance document entitled “Class II Special Controls Guidance Document: Herpes Simplex Virus Types 1 and 2 Serological Assays.” For availability of the guidance revised document, see § 866.1(e).