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510(k) Data Aggregation
(448 days)
Dextramer® CMV Kit is a semi-quantitative assay intended for the identification and enumeration of cytomegalovirus (CMV)-specific CD8+ T cells in anticoagulated (Na Heparin) whole blood specimens by flow cytometry.
Dextramer® CMV Kit is indicated for assessment of CMV-specific immune status and risk of CMV reactivation in adult human stem cell transplant patients following immunosuppression and used in conjunction with other laboratory and clinical findings.
The kit cannot be used to measure CMV infection or disease.
The kit is limited to individuals with the following HLA types: A0101, A0201, B0702, B0801, B*3501.
Special instrument requirements:
FACSCanto II flow cytometer (Becton Dickinson).
The Dextramer® CMV Kit comprises 5 CMV Dextramers, Negative control as well as 3 antibodies recognizing CD3, CD4, and CD8. The Dextramer® CMV Kit accurately enumerates CMV-specific T cells in blood samples. This involves a two-step procedure followed by analysis by flow cytometry:
Step 1: Determination of the percentage of CMV-specific CD3CD8 T cells in the sample (Tube A)
Step 2: Determination of the absolute number of CD3CD8 T-cells in the sample (Tube C)
The absolute number of CMV-specific CD3CD8 T cells/ul blood is then determined.
This document is a 510(k) summary for the Immudex Dextramer® CMV Kit, detailing its substantial equivalence to a predicate device and presenting performance characteristics from non-clinical and clinical studies.
Here's a breakdown of the requested information:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state "acceptance criteria" in the traditional sense (e.g., a specific threshold that must be met for approval for each metric). Instead, it presents performance characteristics. For comparative studies, substantial equivalence based on statistical metrics (slope, intercept, r-value) is used. For clinical studies, a statistically significant risk ratio is the performance indicator.
| Performance Characteristic | Acceptance Criteria (Implicit) | Reported Device Performance |
|---|---|---|
| Non-clinical studies | ||
| Analytical sensitivity | Lowest concentration measurable with acceptable CV% (e.g., <20%) | 1 cell/uL (CV% below 20%) |
| Analytical specificity | CMV seronegative samples should be below the functional assay sensitivity. | 100% (35/35) CMV seronegative samples showed 0.00 - 0.06 cells/ul, below 1 cell/ul. |
| Inter-lab reproducibility | Acceptable CV% range | CV ranged between 6% and 18% |
| Intra-lab reproducibility | Acceptable CV% range | CV ranged between 5% and 14% |
| Linearity - Recovery | Linearity demonstrated across a specified range with acceptable slope and recovery. | Linearity between 1-107 CMV-specific T cells/ul with slope 0.98-1.08. Recovery 73-134%. |
| Interference | No significant interference from tested cell populations. | No significant interference from monocytes (2x normal), granulocytes (3x normal), platelets (3x normal), and red blood cells (2x normal). |
| Cross-reaction | No significant cross-reaction with allele mismatching CMV Dextramer reagents; results should be below functional assay sensitivity. | All results from 4 blood samples with HLA mis-matched CMV Dextramer were within 0.00 - 0.11 cells/ul, below 1 cell/ul. |
| Comparison with predicate | Substantial equivalence based on Deming regression for both CD8+ T-cells and CMV-specific T-cells (slope close to 1, intercept close to 0, high r). | CD8+ T-cells: Slope 0.984 (95% CI: 0.92 to 1.05), Intercept -0.4406 (95% CI: -8.47 to 7.59), r 0.905. |
| CMV-specific T-cells: Slope 1.010 (95% CI: 0.89 to 1.13), Intercept 0.39 (95% CI: 0.09 to 0.69), r 0.952. | ||
| Clinical studies | ||
| Risk of antigenemia | Statistically significant correlation between CMV-specific T-cell status and risk of CMV antigenemia. | Relative Risk of developing antigenemia is 3.4 (95% CI: 1.57 - 7.46) for patients with < 7 cells/uL CMV-specific CD8+ T cells compared to patients with ≥ 7 cells/uL (at Day 100 post-transplant). Only Day 100 showed significant association. |
2. Sample Size Used for the Test Set and the Data Provenance
- Non-clinical (Analytical specificity, Cross-reaction):
- Analytical specificity: 35 routine blood specimens.
- Cross-reaction: 4 blood samples.
- Provenance: Not specified, but generally analytical studies are conducted in a controlled lab environment.
- Non-clinical (Comparison with predicate):
- 117 MHC multimer measurements from blood specimens of stem cell transplant recipients.
- Provenance: Not specified, but likely from clinical sites or blood banks.
- Clinical Studies:
- Test set: 120 allogeneic SCT patients were followed. The specific numbers used for the 2x2 table for "Risk of developing CMV antigenemia after Day 100" are:
- < 7 cells/ul: 10 patients (9 Yes, 1 No)
- ≥ 7 cells/ul: 19 patients (5 Yes, 14 No)
- Total for this specific analysis: 29 patients.
- Data Provenance: Prospective study with allogeneic SCT patients. Country of origin not specified.
- Test set: 120 allogeneic SCT patients were followed. The specific numbers used for the 2x2 table for "Risk of developing CMV antigenemia after Day 100" are:
3. Number of Experts Used to Establish the Ground Truth for the Test Set and the Qualifications of Those Experts
The document does not mention the use of experts to establish ground truth for the device's performance directly.
- For the non-clinical studies, the ground truth for cell counts and specificities would be based on validated laboratory methods and reference standards.
- For the clinical study, the "ground truth" for CMV antigenemia was based on "recurrence of CMV infection and determination of numbers of CMV-specific CD8+ T cells" and "CMV antigenemia," which are clinical outcomes or standard laboratory diagnoses. No expert panel for ground truth adjudication is indicated.
4. Adjudication Method for the Test Set
Not applicable. There is no indication of an adjudication method by experts for establishing ground truth in this submission. The outcomes (CMV antigenemia, cell counts) are measured or clinically diagnosed.
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
Not applicable. This device is a semi-quantitative assay (a laboratory kit for flow cytometry), not an AI-assisted diagnostic imaging or interpretation tool for human readers. There is no mention of human reader performance or AI assistance.
6. If a Standalone (i.e. algorithm only without human-in-the-loop performance) was Done
The device itself is a standalone laboratory assay (kit) that is used with a flow cytometer. The performance characteristics described are for the kit's ability to identify and enumerate CMV-specific T cells, which is essentially its "standalone" performance. There isn't an "algorithm" in the typical sense of AI, but the kit and its associated flow cytometry analysis constitute the device's standalone operation.
7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc)
- Non-clinical studies: The ground truth for analytical performance (sensitivity, specificity, reproducibility, linearity, cross-reactivity) is inherently based on the known quantities/characteristics of the samples used in the experiments. For the "Comparison with predicate," the predicate device's results are used as a reference point for substantial equivalence.
- Clinical studies: The ground truth for the clinical correlation (risk of antigenemia) is clinical outcomes data (development of CMV antigenemia) and the enumeration of CMV-specific CD8+ T cells by the device itself and the predicate. CMV antigenemia is a laboratory-confirmed clinical event.
8. The Sample Size for the Training Set
The document does not detail a separate "training set" for the Dextramer CMV Kit, as it is a laboratory assay kit and not a machine learning algorithm that typically undergoes a distinct training phase. The development and validation of such a kit would involve internal experiments and optimization, but these are not typically referred to as a "training set" in the context of device approval documents like this.
9. How the Ground Truth for the Training Set Was Established
Not applicable, as a distinct "training set" in the context of machine learning and its associated ground truth establishment is not described for this device. The kit's components and methodology are based on established scientific principles in immunology and flow cytometry.
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