(303 days)
The Light Diagnostics™ HSV 1/2 Typing DFA Kit is an in vitro diagnostic test for the qualitative detection and identification of herpes simplex virus type 1 and/or type 2 in direct specimens from patients with vesicular lesions and symptoms consistent with herpes infection and for culture confirmation by immunofluorescence. Negative results do not preclude an infection and should not be used as the sole basis for diagnosis, treatment or other management decisions. Specimens found negative on direct specimen detection should be confirmed by culture.
For In Vitro Diagnostic Use.
Light Diagnostics™ HSV 1/2 Typing DFA Kit is a qualitative test that uses specific typing reagents and FITC filter fluorescence microscope to detect and differentiate herpes simplex viruses 1 and 2 in direct specimens from symptomatic patients with lesions and in specimens amplified by cell culture. The kit consists of HSV-1 Typing Reagent vial, HSV-2 Typing Reagent vial, two HSV Control Slides, Phosphate-Buffered Saline packet; Tween 20/Sodium Azide Solution (100X) vial, and Mounting Fluid vial. The kit utilizes specific reagents for the detection and identification of HSV-1 and HSV-2, therefore two cell spots on slides of specimens are required to identify the type of HSV. The HSV-1 Typing Reagent consists of two fluorescein-labeled monoclonal antibodies specific for HSV-1 glycoprotein C and ICP35 respectively. The HSV-2 Typing Reagent consists of two fluorescein-labeled monoclonal antibodies that specifically bind HSV-2 polypeptides. In Western blots these appear as two major bands with molecular weights of between 110-120 kD and between 78-82 kD and are consistent with the monoclonal antibodies recognizing epitopes within glycoprotein G of HSV-2. The typing reagents will bind to HSV-1 or HSV-2 infected cells fixed on microscope slides specifically. Separate cell spots on slides should be prepared for use with each reagent. Unbound reagent is removed by rinsing with phosphate-buffered saline (PBS). Illumination with ultraviolet light allows visualization of the antigen-antibody complexes by fluorescence microscopy. HSV-infected cells will exhibit apple-green fluorescence with the specific reagent while cells stain a dull red due to the presence of Evans blue in the typing reagents. The controls contained in this kit are acetone fixed slides with one well containing HSV-1 infected cells, one well containing HSV-2 infected cells, and one well containing uninfected cells to verify functioning of reagents, culture methodology and functioning of the microscope.
Here's a summary of the acceptance criteria and the study that proves the device meets them, 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., "Sensitivity must be >= X%"). Instead, it presents the performance characteristics found and concludes that they demonstrate substantial equivalence to the predicate device. The comparison studies were performed against "Culture Confirmation with HSV typing reagent," which served as the reference standard.
| Performance Metric | Acceptance Criteria (Implicit - based on predicate equivalence) | Reported Device Performance (Light Diagnostics™ HSV 1/2 Typing DFA Kit) |
|---|---|---|
| Direct Specimen Testing | ||
| HSV-1 Sensitivity | Comparable to predicate device/culture | 84% (87/104) (95% CI: 75-90%) |
| HSV-1 Specificity | Comparable to predicate device/culture | 99% (331/334) (95% CI: 97-99%) |
| HSV-2 Sensitivity | Comparable to predicate device/culture | 85% (57/67) (95% CI: 75-92%) |
| HSV-2 Specificity | Comparable to predicate device/culture | 99% (367/369) (95% CI: 98-99%) |
| Culture Testing (Amplified Specimens) | ||
| HSV-1 Sensitivity | Comparable to predicate device/culture | 100% (105/105) (95% CI: 97-100%) |
| HSV-1 Specificity | Comparable to predicate device/culture | 100% (71/71) (95% CI: 95-100%) |
| HSV-2 Sensitivity | Comparable to predicate device/culture | 100% (70/70) (95% CI: 97-100%) |
| HSV-2 Specificity | Comparable to predicate device/culture | 100% (106/106) (95% CI: 97-100%) |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Direct Specimen Testing:
- Total collected: 454 specimens
- Excluded for HSV-1 direct analysis due to insufficient cells: 16 specimens
- Excluded for HSV-2 direct analysis due to insufficient cells: 18 specimens
- Culture results not recorded for: 3 specimens
- Effective Sample Size (HSV-1 Direct): 438 specimens (454 - 16)
- Effective Sample Size (HSV-2 Direct): 436 specimens (454 - 18)
- Sample Size for Culture Testing (Amplified Specimens):
- Total: 176 specimens (from the initial 454 specimens that grew on culture)
- Data Provenance: Clinical specimens were collected from three sites in the United States: 258 samples from the Eastern region and 196 from the Southeastern region. The study explicitly states it was a "Clinical Evaluation" using "specimens collected from three sites from symptomatic patients with lesions," indicating a prospective collection of real-world patient samples.
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 involved in establishing the ground truth. It states that "Culture Confirmation with HSV typing reagent" was used as the reference standard. For direct specimen analysis, fluorescence microscopy was used to examine slides stained with the Light Diagnostics™ kit and a reference HSV typing reagent. For cell culture, observers would typically assess cytopathic effect (CPE) for the presence of HSV. The interpretation of these methods would usually be performed by trained laboratory personnel or clinical microbiologists, but no specific details on their number or qualifications are provided.
4. Adjudication Method for the Test Set
The document does not describe a formal adjudication method (e.g., 2+1, 3+1). The reference standard for comparison was "Culture Confirmation with HSV typing reagent." It implies a direct comparison of the investigational device's results against this established reference, rather than a multi-reader adjudication process for the ground truth itself.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly described. The study focuses on evaluating the performance of the device against a predicate or reference method (cell culture with HSV typing reagent) rather than assessing human reader improvement with or without AI assistance. The device itself is an immunofluorescence assay kit, not an AI-based system.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, in a sense, a standalone performance was done. The Light Diagnostics™ HSV 1/2 Typing DFA Kit is an in vitro diagnostic test kit. Its "performance" is measured by its ability to detect and differentiate HSV-1 and HSV-2 antigens in patient samples via immunofluorescence without human "interpretation assistance" beyond standard laboratory procedures (e.g., slide reading under a microscope). The results presented (sensitivity and specificity) represent the performance of the kit itself when compared to the reference standard. There is no AI algorithm involved.
7. The Type of Ground Truth Used
The primary ground truth used was molecular/biological confirmation via cell culture (with HSV typing reagent). For direct specimen testing, the device's results were compared to "culture isolation." For culture testing (amplified specimens), the device's performance was compared against a "Predicate HSV typing reagent" used on culture-amplified specimens. This implies that the presence or absence and typing of HSV were determined by cell culture methods and confirmed with a reference HSV typing reagent.
8. The Sample Size for the Training Set
The document does not describe a "training set" in the context of machine learning or AI. This is a traditional in vitro diagnostic device, and thus, the concept of a training set for an algorithm is not applicable. The non-clinical evaluations involving reference strains and clinical isolates (e.g., 8 HSV-1 isolates, 7 HSV-2 isolates, other viruses, bacteria, and cell lines) served as an internal validation and specificity check (see "Non-clinical evaluation" section), rather than a training set for an algorithm.
9. How the Ground Truth for the Training Set Was Established
As there is no "training set" in the AI sense, this question is not applicable. For the non-clinical evaluation, the ground truth was established by using known reference strains (e.g., ATCC VR733/735 for HSV-1, ATCC VR734 for HSV-2) and "previously typed clinical isolates," indicating these were characterized and verified prior to being used in the specificity assessment.
§ 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).