(275 days)
An enzyme linked immunoassay (ELISA) for the qualitative or semi-quantitative detection of anti-centromere IgG antibodies in human serum as an aid in diagnosis of limited cutanteous systemic sclerosis / CREST in conjunction with other laboratory and clinical findings.
An enzyme linked immunoassay (EUSA) for the qualitative detection of anti-centromere IgG antibodies in human serum as an aid in diagnosis of limited cutaneous systemic sclerosis / CREST in conjunction with other laboratory and clinical findings.
This test is performed as a solid phase immunoassay. Microwells are coated with recombinant purified CENP-A centromere antigens. Controls, calibrators and patient sera are incubated in the antigen coated wells to allow specific antibodies present in the serum to bind to the centromere antibodies are detected by adding an enzyme labeled anti-human lgG conjugate. Specific enzyme substrate (TMB) is then added and the presence of antibodies is detected by a color change that is read by a spectrophotometer at 450 nm. Results are expressed in ELISA units per milliliter (EU/ml) and reported as positive or negative.
Here's an analysis of the provided text regarding the ImmuLisa™ Enhanced Centromere Antibody ELISA, focusing on acceptance criteria and supporting studies:
1. Table of Acceptance Criteria and Reported Device Performance
The document doesn't explicitly state formal "acceptance criteria" in a numerical target format (e.g., "sensitivity must be > X%"). Instead, the performance is demonstrated and presented for comparison to the predicate device and in clinical utility. Therefore, the reported performance metrics are presented in the table as the de facto "acceptance criteria" based on the study findings.
| Metric | Acceptance Criteria (Implied) | Reported Device Performance (ImmuLisa™) |
|---|---|---|
| Method Comparison (vs. Predicate INOVA QUANTA Lite™ Centromere ELISA) | ||
| Positive Percent Agreement (PPA) | High agreement with predicate | 93.2% (95% CI 82.7% - 97.8%) |
| Negative Percent Agreement (NPA) | High agreement with predicate | 95.4% (95% CI 92.5% - 97.3%) |
| Overall Agreement | High agreement with predicate | 95.1% (95% CI 92.4% - 96.9%) |
| Cross-Reactivity | Low false positives in other conditions | 2.7% (18/669 samples) |
| Precision | Low imprecision (CV%) across range | Total CV% range: 3.5% - 7.0% |
| Reproducibility (Qualitative) | High qualitative agreement | 62.5% for cutoff samples, 100% for ~20% above cutoff and other moderate positive samples. |
| Limit of Detection (LoD) | Clearly defined LoD | 3.9 EU/ml |
| Linearity and Recovery | Good linearity and recovery across assay range | Slope: 1.02-1.05, R²: 0.9842-0.9947, Recovery: 87%-116% |
| Hook Effect | No hook effect demonstrated | Not demonstrated up to 2531.3 EU/ml |
| Clinical Sensitivity (for IcSSc/CREST) | Demonstrate clinical utility | 53.2% (with 124 IcSSc/CREST samples) |
| Clinical Specificity (vs. autoimmune/infectious disease controls) | Demonstrate clinical utility | 95.5% (with 865 control samples) |
2. Sample Size Used for the Test Set and Data Provenance
- Method Comparison Test Set: 407 samples (59 positive, 348 negative by predicate).
- Cross-Reactivity Test Set: 669 specimens from individuals with various autoimmune or infectious diseases.
- Precision Test Set: 7 patient samples, run in duplicate, twice per day for 20 days (n=80 replicates per sample).
- Reproducibility Test Set: Samples ranging from ~20% below cutoff, ~20% above cutoff, and in the moderate positive range. Run in duplicate twice per day for 20 days.
- Limit of Detection Test Set: 60 replicates of blank, 10 replicates each of 6 low-level samples.
- Clinical Test Set: 124 IcSSc/CREST samples and 865 autoimmune and infectious disease controls.
Data Provenance: The document does not explicitly state the country of origin for the samples or whether they were retrospectively or prospectively collected. "Well-characterized lcSSc / CREST subjects and disease controls" are mentioned for the method comparison, suggesting pre-existing characterized samples. The clinical tests also use "Sets of clinical samples." Without further information, it's difficult to determine the specific provenance or collection method.
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 used to establish the ground truth for the test sets. For the method comparison, it refers to "well-characterized lcSSc / CREST subjects and disease controls," which implies clinical diagnosis, but the process of this characterization is not detailed. The "clinical tests" used IcSSc/CREST samples and controls, which would have had prior clinical diagnoses, but the adjudication of these diagnoses for the purpose of the study is not explained.
4. Adjudication Method for the Test Set
The document does not describe any specific adjudication method (e.g., 2+1, 3+1, none) for establishing the ground truth of the test set samples. The ground truth appears to be based on prior clinical diagnoses or characterization, but the details of how these were confirmed or adjudicated for the study are not provided.
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 done. The device is an immunoassay (ELISA) for detecting antibodies, not an imaging or diagnostic algorithm that human readers would interact with.
6. If a Standalone (i.e., Algorithm Only Without Human-in-the-Loop Performance) Was Done
Yes, this is a standalone performance study. The ImmuLisa™ Enhanced Centromere Antibody ELISA is an in-vitro diagnostic device designed to provide results directly. Its performance (e.g., sensitivity, specificity, agreement) is assessed independently of direct human intervention in the result interpretation beyond standard laboratory procedures for running the assay and reading the spectrophotometer. The results are expressed quantitatively (EU/ml) and then interpreted qualitatively (positive/negative) based on a defined cutoff.
7. The Type of Ground Truth Used
The ground truth for the test sets (especially for method comparison and clinical performance) appears to be expert consensus / clinical diagnosis.
- For the Method Comparison, samples were "well-characterized lcSSc / CREST subjects and disease controls," implying pre-established clinical diagnoses.
- For Clinical Tests, "IcSSc/CREST samples" and "autoimmune and infectious disease controls" were used, again relying on existing clinical diagnoses as the reference standard.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of device development or algorithm training. This is expected as the ImmuLisa™ is an ELISA kit, which relies on biochemical reactions and calibrated readouts rather than machine learning algorithms that typically require training data. The development of the assay itself would involve optimization and calibration, but this is distinct from "training a model."
9. How the Ground Truth for the Training Set Was Established
As no "training set" in the machine learning sense is described or implied for this ELISA kit, the question of how its ground truth was established is not applicable. The development of such diagnostic kits involves rigorous assay design, optimization, and validation against known standards and clinically characterized samples, but this is a different paradigm than algorithm training.
§ 866.5100 Antinuclear antibody immunological test system.
(a)
Identification. An antinuclear antibody immunological test system is a device that consists of the reagents used to measure by immunochemical techniques the autoimmune antibodies in serum, other body fluids, and tissues that react with cellular nuclear constituents (molecules present in the nucleus of a cell, such as ribonucleic acid, deoxyribonucleic acid, or nuclear proteins). The measurements aid in the diagnosis of systemic lupus erythematosus (a multisystem autoimmune disease in which antibodies attack the victim's own tissues), hepatitis (a liver disease), rheumatoid arthritis, Sjögren's syndrome (arthritis with inflammation of the eye, eyelid, and salivary glands), and systemic sclerosis (chronic hardening and shrinking of many body tissues).(b)
Classification. Class II (performance standards).