(212 days)
The LOCI Vitamin D Total assay is an in vitro diagnostic test for the quantitative measurement of total 25(OH)yitamin D in human serum and plasma on the Dimension® EXL™ integrated chemistry system with LOCI® Module. Measurements of vitamin D are used in the assessment of vitamin D sufficiency.
The LOCI VITD CAL is an in vitro diagnostic product for the calibration of the Vitamin D (VITD) Total assay on the Dimension® EXL™ integrated chemistry system with LOCI® module.
LOCI Vitamin D Total assay:
The LOCI Vitamin D Total assay is a homogeneous competitive chemiluminescent immunoassay based on LOCI technology. The assay measures the total 25(OH)vitamin D concentration [comprising both 25(OH)vitamin D2 and 25(OH)vitamin D3] in both serum and plasma. LOCI Vitamin D Total reagents include a releasing reagent, biotinylated monoclonal antibody, and two synthetic bead reagents. Patient sample is incubated with the releasing reagent to release 25(OH)vitamin D molecules from the vitamin D-binding proteins. The reaction mixture is then incubated with biotinylated antibody to form a 25(OH)vitamin D/biotinylated antibody complex.
Chemibeads containing 25(OH)vitamin D3 analog and chemiluminescent dye are added to remove the excess free biotinylated antibody. Streptavidin-coated Sensibeads containing a photosensitive dye are added to bind the biotinylated antibody. Aqqregates of the Chemibead analog/biotinylated antibody/streptavidin Sensibeads are formed as a result. Illumination of the reaction mixture by light at 680 nm generates singlet oxygen from the Sensibeads, which diffuses into the Chemibeads and triagers a chemiluminescent reaction. The resulting chemiluminescent signal is measured at 612 nm and is inversely proportional to the concentration of total 25(OH)vitamin D in the sample.
LOCI VITD CAL:
The LOCI VITD CAL is a five level, liquid, single analyte, frozen product, which is stored at -15 ℃ to -25 ℃. The calibrator matrix consists of processed human serum with preservatives and stabilizers. Level 1 is a zero level, while levels 2 3, 4, and 5 contain approximately 12, 30, 75, and 165 ng/mL respectively. Each lot of calibrators will have lot specific assigned values assigned from master pool levels that are traceable by method correlation to Ghent University's ID-LC/MS/MS 25(OH)vitamin D Reference Method Procedure (RMP). The ID-LC/MS/MS RMP is traceable to the NIST SRM 2972.
Here's an analysis of the provided text regarding the LOCI Vitamin D Total Assay and LOCI VITD CAL, focusing on acceptance criteria and the supporting studies:
Summary of Acceptance Criteria and Device Performance for LOCI Vitamin D Total Assay
Unfortunately, the provided document does not explicitly state predetermined "acceptance criteria" for each performance characteristic in a table format, nor does it provide a direct statement "proving the device meets acceptance criteria."
Instead, the document describes the methods and presents the results of various performance studies. The implication is that these results demonstrate the device's acceptable performance for its intended use, based on generally accepted analytical performance standards in the medical device industry (e.g., CLSI guidelines).
However, I can extract the reported performance and infer what aspects would likely be critical for acceptance.
1. Table of Acceptance Criteria (Inferred) and Reported Device Performance
| Performance Characteristic | Inferred Acceptance Criterion (Typical for IVDs) | Reported Device Performance (LOCI Vitamin D Total Assay) |
|---|---|---|
| Method Comparison | Slope ~1.0, Intercept ~0.0, r > 0.95 | Slope: 1.06 (95% CI: 1.01 to 1.12) |
| Intercept: 0.44 ng/mL (95% CI: -0.54 to 1.42) | ||
| r-Value: 0.977 | ||
| Repeatability (within-run precision) | %CV 0.99, % bias 0.95 | Lithium heparin plasma vs serum: Slope 0.99, Intercept 0.1, r 0.992 |
| EDTA plasma vs serum: Slope 0.98, Intercept 1.4, r 0.997 | ||
| Serum SST vs serum: Slope 0.99, Intercept 0.5, r 0.997 | ||
| Cross-Reactivity | Specificity to 25(OH)vitamin D2/D3, low cross-reactivity with other D metabolites | 25(OH)D2: 94-95% |
| 25(OH)D3: 89-90% | ||
| 1,25(OH)2D2: 1.3-151.9% (high at low VitD) | ||
| 1,25(OH)2D3: -224.5-1.7% (variable) | ||
| Paricalcitol: 71-94% |
2. Sample Size Used for the Test Set and Data Provenance
- Method Comparison:
- Sample Size: 163 remnant de-identified human serum samples.
- Data Provenance: Not explicitly stated, but "human serum samples" implies human origin. "Remnant de-identified" suggests retrospective data.
- Repeatability and Within Lab Precision:
- Sample Size: Testing performed with Tri-Level Vitamin D Plus QC (3 levels) and 4 human serum/plasma samples (Serum 1, Serum 2, Serum 3, Plasma 2). Each sample/QC was analyzed as a single test from two independent cups, over 20 days with 2 runs per day.
- Data Provenance: Not specified, but laboratory-controlled samples/QCs and potentially remnant human samples.
- Linearity:
- Sample Size: One sample with high concentration serially diluted. Each dilution assayed in n=5 replicates.
- Data Provenance: Laboratory prepared samples.
- Recovery:
- Sample Size: Two separate serum samples (baseline 28.3 ng/mL and 54.7 ng/mL) were spiked.
- Data Provenance: Human serum.
- Detection Capability (LoD, LoB):
- Sample Size: 120 determinations (60 blank and 60 low-level replicates).
- Data Provenance: Laboratory prepared blank and low-level samples.
- Interference Testing (HIL & Non-Interfering Substances):
- Sample Size: Not explicitly stated per interferent, but tested at three levels of vitamin D concentrations (13.9-16.9 ng/mL, 28.4-32.0 ng/mL, 70.2-77.3 ng/mL).
- Data Provenance: Laboratory prepared samples spiked with interferents.
- HAMA Interference:
- Sample Size: 20 samples containing vitamin D (5.0 ng/mL to 87.5 ng/mL) with varying concentrations of HAMA (8 ng/mL to 161,000 ng/mL). Mean n=5 for bias calculations.
- Data Provenance: Human samples containing HAMA.
- Serum Plasma Equivalency:
- Sample Size: 70 matched lithium heparin plasma, K2 EDTA plasma, serum separator tube (SST), and red top serum samples. 8 were fresh native, 62 frozen (8 of these split and spiked).
- Data Provenance: Human patient samples (U.S. geographical locations, potentially diverse, during different seasons). Indicated as remnant, de-identified and includes both fresh and frozen samples. This is a mix of prospective (freshly drawn) and retrospective (remnant, frozen) data from human patients in the US.
- Cross-Reactivity:
- Sample Size: Not explicitly stated per cross-reactant, but tested at specified concentrations.
- Data Provenance: Laboratory prepared samples spiked with cross-reactants.
- Apparently Healthy Population (Expected Values):
- Sample Size: 252 adults (246 not taking supplements, 6 taking).
- Data Provenance: Human serum samples collected from subjects residing in diverse U.S. geographical locations, during different seasons.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications
- Ground Truth for Method Comparison: The "ground truth" for the method comparison study was established by the ID-LC-MS/MS 25(OH) vitamin D Reference Measurement Procedure (RMP) from Ghent University, which is traceable to the NIST Standard SRM2972. This is a highly specialized analytical method, not typically performed by "experts" in the sense of a medical professional consensus. It's a gold-standard laboratory technique.
- Other Studies: For other performance characteristics, the ground truth is based on the known concentrations of controls, calibrators, spiked samples, or reference materials, which are established through rigorous analytical methodology rather than expert consensus on a clinical case.
4. Adjudication Method for the Test Set
This type of information (e.g., 2+1, 3+1 for clinical consensus) is not applicable to an in vitro diagnostic (IVD) assay product like the LOCI Vitamin D Total Assay. Adjudication methods are typically used in imaging studies or clinical trials where human interpretation of data (e.g., images, patient symptoms) is subject to variability and requires consensus among experts to establish a "ground truth" or clinical outcome. For IVD assays, the "ground truth" is largely analytical, based on reference methods or known concentrations.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and Effect Size of Human Reader Improvement
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This type of study is primarily relevant for medical imaging AI devices where human readers interpret images, and the AI serves as an aid. The LOCI Vitamin D Total Assay is an automated in vitro diagnostic assay, where the output is a quantitative measurement, not an image requiring human interpretation or a "reader."
6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done
The entire set of performance characteristic studies for the LOCI Vitamin D Total Assay (e.g., precision, linearity, method comparison, interference) evaluates the standalone performance of the assay. It's an automated system (Dimension EXL integrated chemistry system with LOCI Module), and the results presented reflect the assay's output without direct human "in-the-loop" interpretation for each individual test result beyond the initial setup and quality control.
7. The Type of Ground Truth Used
The ground truth used for the critical method comparison study and calibrator traceability is traceability to a reference measurement procedure (RMP) and standard reference materials (SRM):
- For Method Comparison: Ghent University's ID-LC-MS/MS 25(OH) vitamin D Reference Measurement Procedure (RMP), traceable to NIST SRM 2972. This is considered a highly accurate and precise analytical "gold standard."
- For Calibrators (LOCI VITD CAL): Internal standards traceable by method correlation to Ghent University's ID-LC-MS/MS 25(OH) vitamin D RMP, which is traceable to NIST SRM 2972.
- For other studies (e.g., precision, linearity, recovery, detection capability, interference): Known concentrations of controls, calibrators, or prepared spiked samples.
8. The Sample Size for the Training Set
The document does not provide information about a "training set" because this is an in vitro diagnostic assay, not an AI/ML algorithm that requires an explicit training phase on a dataset of patient results. The development process for such assays involves extensive R&D, reagent formulation, and analytical validation but not "training" in the machine learning sense.
9. How the Ground Truth for the Training Set Was Established
Since there is no explicit "training set" in the context of an AI/ML algorithm, this question is not applicable as per the understanding derived from the document. The "ground truth" for the analytical performance of the assay and its calibrators is established as described in point 7.
§ 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.