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510(k) Data Aggregation
(123 days)
The Focus Diagnostics Plexus™ HerpeSelect® HSV 1 and 2 IgG (with software) is intended for qualitatively detecting the presence or absence of human IgG antibodies to HSV-1 and HSV-2 in human sera. The test is indicated for pregnant women and sexually active adults, as an aid for presumptively diagnosing HSV-1 and HSV-2 infection. The predictive value of a positive or negative result depends on the population's prevalence and the pretest likelihood of HSV-1 and HSV-2 infection. The test is not intended for donor screening or for self-testing. The performance of this assay has not been established for use in a pediatric population, for neonatal screening, for testing of immunocompromised patients, for use by a point of care facility or for use with automated equipment.
The Focus Diagnostics Plexus™ HerpeSelect® HSV 1 and 2 IgG (with software) is a multiplexed immunoassay for qualitatively detecting and differentiating human IgG antibodies to HSV-2. Test principle is identical to the predicate device.
Here's an analysis of the acceptance criteria and the study that proves the device meets them, based on the provided text:
Device: Plexus™ HerpeSelect® HSV 1 and 2 IgG (with software)
1. Table of Acceptance Criteria and Reported Device Performance
The document doesn't explicitly state "acceptance criteria" in a quantitative manner for all performance aspects. However, the "Summary of Previous Studies for Plexus™ HerpeSelect® HSV 1 and 2 IgG (manual calculation)" table on page 2 provides clear performance metrics that can be interpreted as the device meeting expected performance for a similar predicate device.
For the purpose of this analysis, I will synthesize "acceptance criteria" from the described study results, assuming that the reported performance met the internal and regulatory expectations for market clearance.
| Acceptance Criteria (Inferred from Study Results) | Reported Device Performance (Plexus™ HerpeSelect® HSV 1 and 2 IgG) |
|---|---|
| Agreement with Plexus Software vs. Manual Calculation | |
| HSV-1 Index Agreement | 100% (95% CI: 0.977 - 1.00) for HSV-1 Positives (n=161)100% (95% CI: 0.398 - 1.00) for HSV-1 Equivocal (n=4)100% (95% CI: 0.973 - 1.00) for HSV-1 Negatives (n=134) |
| HSV-2 Index Agreement | 100% (95% CI: 0.974 - 1.00) for HSV-2 Positives (n=139)100% (95% CI: 0.590 - 1.00) for HSV-2 Equivocal (n=7)100% (95% CI: 0.976 - 1.00) for HSV-2 Negatives (n=153) |
| Performance in Indicated Populations | |
| Pregnant Women HSV-1 Specificity | 96.5% (95%CI 92.5-98.7%) |
| Pregnant Women HSV-1 Sensitivity | 92.2% (95%CI 86.1-96.2%) |
| Pregnant Women HSV-2 Specificity | 94.3% (95%CI 88.5-97.7%) |
| Pregnant Women HSV-2 Sensitivity | 95.5% (95%CI 91.2-98.0%) |
| Sexually Active Adults HSV-1 Specificity | 91.0% (95%CI 85.4-95.0%) |
| Sexually Active Adults HSV-1 Sensitivity | 96.5% (95%CI 92.0-98.9%) |
| Sexually Active Adults HSV-2 Specificity | 96.3% (95%CI 90.9-99.0%) |
| Sexually Active Adults HSV-2 Sensitivity | 97.4% (95%CI 93.9-99.1%) |
| Agreement with CDC HSV/CMV Panel | |
| Agreement with HSV-1 Positives | 100% (54/54), 95%CI 89.1-100% (for HSV-1 Positive only), 95%CI 84.6-100% (for Dual Positive) |
| Agreement with HSV-2 Positives | 100% (36/36), 95%CI 76.8-100% (for HSV-2 Positive only), 95%CI 84.6-100% (for Dual Positive) |
| Agreement with Negatives | 100% (32/32), 95%CI 89.1-100% (for Dual Negative) |
| Performance in Low Prevalence Population | |
| Low Prevalence HSV-1 Agreement with Negatives | 97.9% (46/47), 95%CI 88.7-99.9% |
| Low Prevalence HSV-2 Agreement with Negatives | 100% (71/71), 95%CI 94.9-100% |
| Cross-reactivity | |
| HSV-1 Cross-reactivity: CMV, EBV, VZV combined | 0-5% observed (e.g., 5.0% for CMV, 3.0% for VZV, 3.1% for EBV, for samples that were HSV-1 ELISA dual negative but positive for other viruses). Specifically, for dual negatives: One out of 37 samples was HSV-1 equivocal/positive, which was triple positive for CMV, VZV, EBV. |
| HSV-2 Cross-reactivity: CMV, EBV, VZV combined | 0-3% observed (e.g., 0.0% for CMV, 2.9% for VZV, 3.2% for EBV, for samples that were HSV-2 ELISA dual negative but positive for other viruses). Specifically, for dual negatives: One out of 37 samples was HSV-2 equivocal/positive, which was positive for VZV and EBV. |
| Reproducibility | |
| %CV of Positives (Inter/Intra-assay, Inter-Lab) | ≤10% for most positive samples, with some acceptable variations (e.g., Sample 9 HSV-1 Inter-assay %CV was 10.3%, Sample 3 HSV-1 Inter-assay %CV was 14.9%, HSV-2 Sample 3 Inter-assay %CV was 28.3%) |
| Inter-Lot %CV | Generally <15% for most positive samples, with higher CVs for very low index samples (e.g., Sample 3 HSV-1 Inter-Lot %CV was 17.0%, Sample 3 HSV-2 Inter-Lot %CV was 50.9%, Sample 10 HSV-1 Inter-Lot %CV was 50.6%) |
2. Sample Sizes and Data Provenance for Test Sets
-
Software Validation Test Set (Agreement between Plexus Software and Manual Calculation):
- Sample Size: n = 600 total (161 HSV-1 Pos, 4 HSV-1 Eqv, 134 HSV-1 Neg, 1 invalid; 139 HSV-2 Pos, 7 HSV-2 Eqv, 153 HSV-2 Neg, 1 invalid).
- Data Provenance: Not explicitly stated regarding country of origin, but described as "Testing was done at two external sites and one internal site." This suggests multiple US-based labs. The study describes it as confirming internal and external consistency rather than a primary clinical validation. It is retrospective since it compares software calculations to existing manual calculations.
-
Clinical Studies Test Sets (Sensitivity and Specificity):
- Sexually Active Adults: n = 300 (150 from Focus Diagnostics, 150 from an external investigator). Sera were "sequentially submitted to the laboratory, archived, and masked."
- Data Provenance: Sera were collected in the Pacific Northwestern United States. One external site was a clinical laboratory in Southern California. Retrospective (archived).
- Pregnant Women: n = 300 (150 from Focus Diagnostics, 150 from an external investigator). Sera were "sequentially submitted to the laboratory, archived, and masked."
- Data Provenance: Sera were collected in the Pacific Northwestern United States. The external investigator was a University laboratory in Northern California. Retrospective (archived).
- CDC HSV/CMV Panel: n = 100 samples (consisting of 50 unique sera with duplicates).
- Data Provenance: Obtained from the CDC. This is a characterized, masked reference panel. Retrospective.
- Low Prevalence Population: n = 77. Sera were "sequentially selected, archived and masked."
- Data Provenance: Sera from patients aged 18-19, submitted to a clinical laboratory in Southern California from states "having a history of low sexually transmitted disease prevalence." Retrospective (archived).
- Cross-reactivity: n = 51 (37 HSV ELISA dual negative, 14 HSV ELISA mixed sero-reactivity).
- Data Provenance: Not explicitly stated, likely internal/archived samples. Retrospective.
- Reproducibility (Inter-laboratory, Inter/Intra-assay, Inter-Lot): Not specified sample provenance for the 11 tested samples, likely contrived or well-characterized internal samples.
- Sexually Active Adults: n = 300 (150 from Focus Diagnostics, 150 from an external investigator). Sera were "sequentially submitted to the laboratory, archived, and masked."
3. Number of Experts and Qualifications for Ground Truth
The document does not describe the use of "experts" to establish ground truth in the traditional sense of medical image interpretation (e.g., radiologists reviewing images). Instead, the ground truth for the serological assays is established by a reference method.
- Reference Method: The primary "gold-standard reference method" used for calculating sensitivity and specificity was the Focus Diagnostics HerpeSelect 1 and 2 Immunoblot IgG. This is a laboratory-based serological test, not one that relies on human expert interpretation of an image or clinical case.
- CDC Panel: The CDC panel itself is a "masked, characterized serum panel" where results (HSV-1, HSV-2, dual positive/negative) are pre-determined by CDC using their own established methods.
Therefore, the concept of "number of experts" and their "qualifications" as typically applied to devices requiring human interpretation (e.g., radiology AI) is not directly applicable here. The ground truth relies on the established accuracy and reliability of the predicate immunoblot assay and the CDC's characterization of their panel.
4. Adjudication Method for the Test Set
Adjudication, in the context of resolving discrepancies between multiple readers or between a device and a reader, is not applicable in this study design.
- The ground truth is established by a single reference method (Immunoblot IgG or CDC's characterization). The new device's results are compared directly to this established ground truth.
- For the "Agreement between Index Calculated with Plexus Software and Index Calculated Manually" study, it's a direct comparison of numerical results. Deviations would be identified as non-agreement, not adjudicated by experts.
5. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study
No, a Multi Reader Multi Case (MRMC) comparative effectiveness study was not performed. This type of study typically assesses how a device (often AI) influences the diagnostic performance of human readers by comparing their performance with and without device assistance. The Plexus™ HerpeSelect® HSV 1 and 2 IgG (with software) is an in vitro diagnostic device, and its performance is evaluated against a predicate serological test, not as an aid for human interpretation.
6. Standalone (Algorithm Only) Performance Study
Yes, a standalone performance study was done. The entire set of performance characteristics presented (sensitivity, specificity, agreement with CDC panel, cross-reactivity, reproducibility) are measures of the algorithm's (device software's) direct performance in interpreting the multiplex immunoassay fluorescent signals to determine HSV-1 and HSV-2 IgG status.
- The study "Agreement between Index Calculated with Plexus Software and Index Calculated Manually" directly validates the software's ability to process raw data and generate results.
- All subsequent clinical performance studies compare the device's output (as determined by the software) directly against a reference method. Therefore, all reported performance metrics relate to the standalone performance of the Plexus™ HerpeSelect® HSV 1 and 2 IgG (with software).
7. Type of Ground Truth Used
The primary type of ground truth used was expert consensus (through an established reference method):
- Established Reference Method: The Focus Diagnostics HerpeSelect 1 and 2 Immunoblot IgG served as the "gold-standard reference method" for sensitivity and specificity calculations in the pregnant women and sexually active adults cohorts, as well as the low prevalence population. Immunoblot assays are considered highly accurate and specific for HSV typing.
- Characterized Panel: For the CDC panel, the ground truth was based on the CDC's characterization of the serum samples. This implies a rigorous, multi-method approach by a recognized authority to establish the true serostatus of the samples.
8. Sample Size for the Training Set
The document does not explicitly state the sample size for the training set. The provided information focuses entirely on validation/test sets to demonstrate the performance characteristics of the finalized device and its associated software. For in vitro diagnostic devices like this, training data might implicitly refer to samples used during the development and optimization phases of the assay and software, which are not typically detailed in 510(k) summaries.
9. How the Ground Truth for the Training Set Was Established
Since no explicit training set is described, information on how its ground truth was established is not provided in this document. During the development of such an assay, the ground truth for any internal training or optimization samples would typically be established using similar or earlier versions of highly accurate reference methods, potentially including culture confirmation, Western blot, or other established serological tests.
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