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510(k) Data Aggregation
(64 days)
The assay is intended for use in detecting antibodies in a single serum specimen. The results of the assay are to be used as an aid in the diagnosis of Systemic Lupus Erythematosus (SLE).
The dsDNA Immunoglobulin EIA test system is an enzyme-linked immunosorbent assay (EIA) for the detection and semi-quantitation of Immunoglobulin to dsDNA in human sera.
This document describes the validation of the MarDx dsDNA Immunoglobulin EIA Test System, a device for detecting antibodies to dsDNA in human sera, intended as an aid in diagnosing Systemic Lupus Erythematosus (SLE).
Here's an analysis of the provided information:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state pre-defined acceptance criteria values for sensitivity, specificity, and accuracy for the MarDx dsDNA EIA Test System. Instead, it demonstrates substantial equivalence to a predicate device (Clark ELISA for dsDNA IgG, IgM antibodies) by presenting the comparative performance.
However, based on the results, we can infer the desired performance levels relative to the predicate device. For precision, the acceptance criteria are implicit in the reported Coefficient of Variation (CV) values.
| Performance Metric | Acceptance Criteria (Implied / Achieved) | Reported Device Performance |
|---|---|---|
| Relative Sensitivity | Substantial equivalence to Clark dsDNA test (implicitly, high sensitivity) | 95.0% (38/40 true positives relative to the Clark test) |
| Relative Specificity | Substantial equivalence to Clark dsDNA test (implicitly, high specificity) | 100% (81/81 true negatives relative to the Clark test) |
| Relative Accuracy | Substantial equivalence to Clark dsDNA test (implicitly, high accuracy) | 98.3% (119/121 agreement relative to the Clark test) |
| Intra-Assay Precision (CV) | Generally, <10-15% is considered good for EIA kits. The reported values are generally ≤ 16.29%. | Ranged from 2.32% to 16.29% across 7 sera tested 10 times each on 3 separate days (values for each assay). E.g., for serum 1, CVs were 3.24%, 4.06%, 3.24% for assays 1, 2, 3 respectively. |
| Inter-Assay Precision (CV) | Generally, <10-20% for inter-assay precision. The reported values are generally ≤ 17.78%. | Ranged from 4.67% to 17.78% (Inter Assay column) across 7 sera (n=30 for each serum over 3 days). E.g., for serum 1, Inter Assay CV was 5.48%. |
| Linearity (r value) | Close to 1 (indicating a strong linear relationship between dsDNA Index Value and log2 of dilution). | Ranged from 0.75 to 0.989 for different serum samples. |
| Cross-Reactivity | No significant positive results for non-dsDNA autoimmune antibodies, particularly for the negative controls (Index Value < 1.0 or not "equ"). | Most samples with other specificities (Ro, La, SM, RNP, SCL-70, Jo-1) showed negative results (Index Value < 1.0 and "Interpretation: -"). Two samples (SM and RNP) showed "equ" (equivocal) results, indicating some potential for equivocal cross-reactivity, but not outright positive. |
| International Unit Conversion (r value) | Close to 1 (strong linear relationship between Index Value and log International Units). | r = 0.975 |
2. Sample size used for the test set and the data provenance
Sample Size: 133 patient specimens
- 88 from normal individuals.
- 45 from individuals thought to have autoimmune disease.
(Note: For sensitivity/specificity calculation, equivocal results were excluded, reducing the total to 121: 40 positive and 81 negative relative to the predicate.)
Data Provenance: Not explicitly stated (e.g., country of origin). The study appears to be prospective in the sense that these specific samples were evaluated for the purpose of validating the new device against a predicate, although the samples themselves might have been collected retrospectively. It doesn't specify if they were newly collected for this study.
3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts
The ground truth for the test set (classification of "normal" vs. "autoimmune disease," and subsequently positive/negative for dsDNA antibodies) was not established by human experts in this study. Instead, the "ground truth" was established based on another commercially available dsDNA ELISA assay (Clark ELISA).
- No information is provided on experts establishing the initial clinical status of the 133 patient specimens (i.e., whether they were "normal" or "thought to have autoimmune disease").
- The primary "truth" for the performance metrics (sensitivity, specificity) comes from the predicate Clark dsDNA test.
4. Adjudication method for the test set
Not applicable. The ground truth was established by a predicate test, not by human experts requiring adjudication. Two sera that were positive by the MarDx EIA but negative by the Clark ELISA were additionally tested by Crithidia IFA, which found them to be negative. This acts as a secondary adjudication for those specific discordant cases, but it's not a general adjudication method for the entire test set.
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
- No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done.
- This study is for a laboratory diagnostic kit, not an AI-assisted diagnostic tool for human readers. Therefore, there is no discussion of human reader improvement with or without AI assistance.
6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
Yes, this study represents a standalone performance evaluation of the MarDx dsDNA Immunoglobulin EIA Test System. The device performs the assay and generates a result (Index Value and Interpretation) without human interpretation steps that would be characteristic of, for example, an imaging AI system. The performance metrics (Sensitivity, Specificity, Accuracy, Precision, Linearity, Cross-Reactivity) reflect the device's inherent capability.
7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.)
The primary "ground truth" for evaluating the MarDx dsDNA EIA was its performance relative to a predicate device, specifically the Clark ELISA for dsDNA IgG, IgM antibodies. This predicate device served as the reference standard (comparative effectiveness).
For two specific discordant cases (MarDx positive, Clark negative), Crithidia IFA was used as a secondary method to establish the truth, and these were found to be negative.
8. The sample size for the training set
Not applicable. This device is an immunoassay kit, not a machine learning or AI model that requires a training set in the conventional sense. The test system is based on established biochemical principles and reagents, not on learning from data.
9. How the ground truth for the training set was established
Not applicable. (See point 8).
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