(58 days)
The Access 25(OH) Vitamin D Total assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of total 25-hydroxyvitamin D [25(OH) vitamin D] levels in human serum and plasma using the DxI Access Immunoassay Analyzers. Results are to be used as an aid in the assessment of vitamin D sufficiency.
The Access 25(OH) Vitamin D Total assay is a competitive binding immunoenzymatic assay. The Access 25(OH) Vitamin D Total assay consists of the reagent pack and calibrators. Other items needed to run the assay include substrate and wash buffer. The Access 25(OH) Vitamin D Total assay reagent pack, Access 25(OH) Vitamin D Total assay calibrators, along with the UniCel Dxl Wash Buffer II are designed for use with the Dxl 9000 Access Immunoassav Analyzer in a clinical laboratory setting.
Here's a breakdown of the acceptance criteria and study details for the Access 25(OH) Vitamin D Total assay, based on the provided document:
1. Table of Acceptance Criteria and Reported Device Performance
| Performance Metric | Acceptance Criteria (Target or Range) | Reported Device Performance (Access 25(OH) Vitamin D Total on Dxl 9000 Access) |
|---|---|---|
| Method Comparison: R² | ≥ 0.90 | 0.97 |
| Method Comparison: Slope | 1.00 ± 0.10 | 1.05 (with 95% CI of 0.99 – 1.10) |
| Precision (Within-laboratory total % CV for > 15.0 ng/mL) | Not explicitly stated as acceptance criteria, but implied to be within acceptable clinical limits. | Ranged from 4.3% to 9.0% |
| Precision (Within-laboratory total SD for ≤ 15.0 ng/mL) | Not explicitly stated as acceptance criteria, but implied to be within acceptable clinical limits. | Ranged from 0.09 to 2.2 |
| Linearity | Linear throughout the analytical measuring interval. | Linear throughout the analytical measuring interval of approximately 7.0-120 ng/mL. |
| Limit of Blank (LoB) | Not explicitly stated as acceptance criteria, but implied that the determined LoB should be low enough for clinical utility. | 2.5 ng/mL |
| Limit of Detection (LoD) | Not explicitly stated as acceptance criteria, but implied that the determined LoD should be low enough for clinical utility. | 4.5 ng/mL |
| Limit of Quantitation (LoQ) | ≤ 20% within-lab CV | 7.0 ng/mL (with ≤ 20% within-lab CV) |
2. Sample Size Used for the Test Set and Data Provenance
- Method Comparison: 150 serum samples. The provenance of these samples (country of origin, retrospective/prospective) is not specified in the provided text.
- Precision: Multiple serum samples were tested in duplicate. The exact number of distinct serum samples beyond Sample 1-6 (which represent different concentration levels) is not specified, but each of the 6 samples was tested with N=80 replicates. The provenance is not specified.
- Limit of Blank (LoB): 120 replicates of a zero-analyte sample. The provenance is not specified.
- Limit of Detection (LoD): 8 to 11 serum samples containing low levels of Vitamin D analyte. These samples were tested over five days with one run per day and nine replicates per run for each pack lot, resulting in ≥ 40 replicates minimally required for LoD estimation for each sample on each pack lot tested. The provenance is not specified.
- Limit of Quantitation (LoQ): 10-13 serum samples containing low levels of Vitamin D analyte. Samples were tested in replicates of nine per run with one run per day and five total days on each pack lot and instrument, resulting in a minimum of 40 replicates for each sample on each pack lot. The provenance is not specified.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
This device is an in vitro diagnostic (IVD) assay for quantitative determination of a biomarker (25-hydroxyvitamin D). The ground truth for such assays is established through analytical methods and reference standards, not typically by human expert consensus or pathology review in the way a diagnostic imaging AI might be evaluated.
Therefore:
- Number of experts: Not applicable.
- Qualifications of experts: Not applicable.
The assay is traceable to NIST-Ghent ID-LC-MS/MS, which serves as a highly accurate reference method for establishing the true concentration of Vitamin D in samples.
4. Adjudication Method for the Test Set
Not applicable for this type of IVD assay. The performance is assessed by comparing results directly to reference methods or statistical metrics, not through expert adjudication of qualitative or semi-quantitative interpretations.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done, and the effect size of how much human readers improve with AI vs without AI assistance
Not applicable. This is an automated in vitro diagnostic assay, not an AI-assisted diagnostic imaging tool that would involve human readers.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) was done
Yes, the studies described (Method Comparison, Precision, Linearity, LoB, LoD, LoQ) evaluate the performance of the device (assay on the analyzer) in a standalone fashion, without human interpretation or intervention beyond running the tests according to protocol.
7. The Type of Ground Truth Used
- Method Comparison: The predicate device (Access 25(OH) Vitamin D Total assay run on the Access 2 Immunoassay System, K142373) serves as the comparator or "reference" for this study. While not an absolute ground truth, it's the established method against which the new device on the new instrument is compared for substantial equivalence.
- Precision, Linearity, LoB, LoD, LoQ: These studies rely on the inherent properties of the assay and statistical methodologies (e.g., CLSI guidelines) to characterize the device's analytical performance. The reference standard for traceability for the analyte itself is NIST-Ghent ID-LC-MS/MS. Low-level and zero-analyte samples are used to establish limits.
8. The Sample Size for the Training Set
This document describes the validation studies for a new IVD assay and instrument combination. It does not mention a "training set" in the context of machine learning, as this is a chemical immunoassay, not an AI/ML-based device. The term "training set" is not relevant here.
9. How the Ground Truth for the Training Set Was Established
Not applicable, as there is no "training set" for this type of device.
§ 862.1825 Vitamin D test system.
(a)
Identification. A vitamin D test system is a device intended for use in clinical laboratories for the quantitative determination of 25-hydroxyvitamin D (25-OH-D) and other hydroxylated metabolites of vitamin D in serum or plasma to be used in the assessment of vitamin D sufficiency.(b)
Classification. Class II (special controls). Vitamin D test systems must comply with the following special controls:(1) Labeling in conformance with 21 CFR 809.10 and
(2) Compliance with existing standards of the National Committee on Clinical Laboratory Standards.