(268 days)
The Diagnostic Hybrids, Inc. D3 DFA Herpes Simplex Virus Identification and Typing Kit is intended for use in the qualitative detection and typing of human herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) in cell cultures by immunofluorescence using fluoresceinated monoclonal antibodies (MAbs). Negative results do not rule out an infection and should not be used as the sole basis for diagnosis, treatment or other management decisions. Performance using direct specimen testing has not been evaluated.
The Diagnostic Hybrids, Inc. D3 DFA Herpes Simplex Virus Identification and Typing Kit uses two separate blends of HSV Type-1 (HSV-1) and HSV Type-2 (HSV-2) antigen-specific murine MAbs that are directly labeled with fluorescein for the rapid detection and typing of HSV. The reagents can specifically detect and type either HSV-1 or HSV-2. The HSV-1 MAbs were developed using HSV-1(f) cell lysate as immunogen - one MAb has been determined to be directed against HSV-1 glycoprotein C1; the antigen to the other is undetermined. The HSV-2 MAbs were developed using a HSV-2 recombinant glycoprotein G as immunogen.
Kit Components:
• HSV-1 DFA Reagent - One dropper bottle containing a blend of two fluorescein labeled murine monoclonal antibodies directed against HSV-1 specific glycoproteins. The HSV-1 MAbs were developed using HSV-1(f) cell Ivsate as immunogen - one MAb has been determined to be directed against HSV-1 glycoprotein C1, the antigen to the other is undetermined. The buffered, stabilized, aqueous solution contains Evan's Blue as a counter-stain and 0.1% sodium azide as preservative.
• HSV-2 DFA Reagent - One dropper bottle containing a blend of two fluorescein labeled murine monoclonal antibodies directed against HSV-2 specific glycoproteins. The HSV-2 MAbs were developed using a HSV-2 recombinant glycoprotein G immunogen. The buffered, stabilized, aqueous solution contains Evan's Blue as a counter-stain and 0.1% sodium azide as preservative
• HSV-1/HSV-2 Antigen Control Slides - Individually packaged control slides containing wells with cell culture derived positive and negative control cells. Each slide consists of four wells containing acetone fixed cells; two wells of noninfected cells and one well each of HSV-1 infected cells and HSV-2 infected cells. Each slide is intended to be stained only one time.
• PBS Concentrate - A 40X concentrate consisting of 4% sodium azide in phosphate buffered saline (after dilution to 1X in water, the concentration of sodium azide in the solution is 0.1%).
• Mounting Fluid - an aqueous, buffered, stabilized solution of glycerol and 0.1% sodium azide.
The cells to be tested, on a slide prepared from a tube culture or on a monolayer of cells cultured in a multi-well plate or a coverslip in a shell vial, are fixed in acetone. The HSV-1 DFA Reagent or HSV-2 DFA Reagent is added to the cells to detect the presence of HSV specific viral antigens. After incubating for 15 to 30 minutes at 35° to 37°C, the stained cells are washed with the supplied Phosphate Buffered Saline (PBS). To prepare the slide for examination, a drop of the supplied Mounting Medium is added to the stained cells and a coverslip is placed on the slide. To prepare the centrifuge enhanced cell cultures for examination, a drop of Mounting Fluid is placed on a clean microscope slide. The coverslip is removed from the shell vial and placed on to the Mountina Fluid.
For multi-well plates, monolayers are fixed with an 80% aqueous acetone solution. The HSV DFA Reagent is added to the cells to detect the presence of any HSV specific viral antigens. After incubating for 15 to 30 minutes at 35° to 37°C, the stained cells are washed with the supplied Phosphate Buffered Saline (PBS). Mounting Fluid is added to each well to cover the monolayers.
The slides or wells are examined using a fluorescence microscope equipped with the correct filter combination for FITC at a magnification of 100-400X. Virus infected cells will be stained with bright apple-green fluorescence while uninfected cells will contain no apple-green fluorescence but will fluoresce red by the Evan's Blue counterstain which is included in the HSV DFA Reagent.
If no fluorescent cells are found, report result as, "No herpes simplex virus detected."
If fluorescent cells are found in the HSV-1 DFA Reagent stained monolayer, report result as "Herpes simplex virus type 1 isolated by cell culture". If fluorescent cells are found in the HSV-2 DFA Reagent stained monolaver, report result as "Herpes simplex virus type 2 isolated by cell culture." If fluorescent cells are found in both the HSV-1 and HSV-2 stained wells, the results should be reported as "Herpes simplex virus types 1 and 2 isolated by cell culture".
Included in the kit are HSV-1/HSV-2 Antigen Control Slides. A Control Slide is intended to function as an indicator that the kit reagents are working properly in the test. [The slides are prepared with wells of HSV-1 infected cells, HSV-2 infected cells, and uninfected cells.] Positive and negative controls must demonstrate appropriate staining characteristics for specimen results to be valid. Controls may also aid in the interpretation of test results.
It is recommended that cell culture positive (infected with known HSV isolate) and negative (uninfected cells) controls be run with each assay to provide a means to ensure adequate performance of the cell culture system used. If control cultures fail to perform correctly, results are considered invalid.
Here's a breakdown of the acceptance criteria and study details for the DIAGNOSTIC HYBRIDS, INC. D3 DFA HERPES SIMPLEX VIRUS IDENTIFICATION KIT, based on the provided 510(k) summary:
Acceptance Criteria and Reported Device Performance
The acceptance criteria for this device are implied by the reported performance metrics, specifically the Positive Percent Agreement (PPA) and Negative Percent Agreement (NPA) with comparison devices. While explicit thresholds for "acceptance" are not stated, the high agreement percentages achieved indicate sufficient performance for regulatory clearance.
| Performance Metric | Acceptance Criteria (Implied) | Reported Device Performance (HSV-1) | Reported Device Performance (HSV-2) |
|---|---|---|---|
| Positive Percent Agreement (PPA) | High agreement with predicate | 98.6% (92.7% - 100% CI) | 100% (95.3% - 100% CI) |
| Negative Percent Agreement (NPA) | High agreement with predicate | 100% (98.9% - 100% CI) | 99.7% (98.3% - 100% CI) |
| Analytical Specificity (Cross-Reactivity) | No cross-reactivity with non-HSV microorganisms | No cross-reactivity observed for 59 virus strains, 17 host cell types, 27 bacterial cultures, 1 yeast, and 1 protozoan (except S. aureus with distinguishable punctate staining). | No cross-reactivity observed for 59 virus strains, 17 host cell types, 27 bacterial cultures, 1 yeast, and 1 protozoan (except S. aureus with distinguishable punctate staining). |
Study Details
2. Sample Size and Data Provenance
- Test Set Sample Size: 398 specimens (out of 401 prospectively collected, 3 were excluded due to bacterial contamination).
- Data Provenance: Prospectively collected specimens at three different laboratories. The country of origin is not explicitly stated but implied to be the US given the submission to the FDA.
3. Number of Experts and Qualifications for Ground Truth
The document does not explicitly state the number of experts used to establish the ground truth or their specific qualifications (e.g., radiologist with X years of experience). Instead, the "ground truth" for the clinical study was established by "currently marketed HSV identification kits ('Comparison Devices')". This implies that these comparison devices, which are already cleared and established in clinical practice, served as the reference standard.
4. Adjudication Method
The document does not describe an adjudication method for the test set. The comparison was directly between the D3 DFA HSV ID & Typing Kit and the "Comparison Devices." Discrepancies are simply reported as either the D3 DFA kit being positive and the comparison negative, or vice versa, contributing to the PPA and NPA calculations.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
There is no mention of a Multi-Reader Multi-Case (MRMC) comparative effectiveness study being performed. The study focuses on comparing the new device's performance against existing, marketed identification kits, not on the improvement of human readers with AI assistance. The device is a diagnostic kit, not an AI-assisted interpretation tool for human readers.
6. Standalone Performance Study
Yes, a standalone performance study was done. The entire clinical performance section evaluates the algorithm (kit) only, without human-in-the-loop performance being a variable. The results are reported based on the kit's ability to detect and type HSV-1 and HSV-2 compared to predicate devices.
7. Type of Ground Truth Used
The ground truth used for the clinical performance study was based on diagnostic results from "currently marketed HSV identification kits ('Comparison Devices')". This can be considered a form of reference standard test result.
8. Sample Size for the Training Set
The document does not specify a separate training set or its sample size. The focus is on the performance evaluation of the final device against a clinical test set. The "development" of the monoclonal antibodies involved using HSV-1(f) cell lysate andHSV-2 recombinant glycoprotein G as immunogens, which would be part of the initial development and optimization phase, but not a distinct "training set" in the context of an AI/algorithm.
9. How the Ground Truth for the Training Set was Established
As no specific training set is mentioned in the context of machine learning, the concept of ground truth for a training set is not directly applicable here. The development of the reagents involved using specific antigens (HSV-1(f) cell lysate and HSV-2 recombinant glycoprotein G) to generate type-specific monoclonal antibodies. The analytical specificity (cross-reactivity) was evaluated using known ATCC reference strains, various other microorganisms, and cell types, which served to confirm the expected reactivity and non-reactivity of the reagents during development and validation.
§ 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).