Table 1b.
Characteristics for manual and automated commercial 25OHD assays according to insertrs.
| Platform vendor | Extraction and purification procedures | Assay principle | Equivalence 25OHD2/25OHD3, Cross-reactivity (C3-epi/24,25(OH)2D | Traceability, recovery (%) | LOQ/(LOD) (nmol/L) | Precision, intra-assay, inter-assay, CV (%) |
|---|---|---|---|---|---|---|
| DiaSorin | S/P acetonitrile | RIA, 125I-CC, derivative goat polyclonal Ab | Equivalence: Yes, cross-reactivity: Yes NR/100% | Calibrators traceable to a pure preparation of the 25OHD Ag calculated by spectrophotometry | 6.25a/(4.0) | 11.7% at 21.5 nmol/L, 9.4% at 21.5 nmol/L |
| Immuno Diagnostics Ltd. | S/P 50 μl, NaOH, acetonitrile | RIA, 125I-25OHD | Equivalence: 75%/100%, cross-reactivity: NR/≥100% | Calibrators standardised by UV quantitation, 89–102 at 20 nmol/L | NR/(3.0) | 5.3% at 26 nmol/L, 8.2% at 20 nmol/L |
| Immuno Diagnostic Systems Ltd. | S/P 25 μl, 2-step procedure w/o extraction | ELISA, immobilized anti-25OHD, sheep polyclonal Ab, 25OHD-labeled with biotin HRP/TMB | Equivalence: 75%/≥100%, cross-reactivity NR/≥100% | Calibrators standardised by UV quantitation, 97–105 | NR/(5.0) | 5.3% at 39 nmol/L, 4.6% at 40 nmol/L |
| Immuno Diagnostic Systems Ltd. | S 10 μl, 2-step procedure, Denaturation DBP+NaOH | CLIA, acridinium-labeled anti-25OHD, sheep polyclonal Ab | Equivalence: Yes, cross-reactivity: 1%/NR | Calibrators standardised to ID-LC-/MS/MS) 25OHD RMP; traceable to the NIST SRM 2972, recovery not reported | 17.5/(6.0) | 6.2% at 30 nmol/L, 11.6% at 30 nmol/L |
| DiaSorin, Liaison, Total DiaSorin | CLIA, HRP – isoluminol derivative | Equivalence: Yes, cross-reactivity: 1.3%/NR | Calibrators traceable to UV spectrophotometric analysis | 10.0/(NR) | 3.8% at 20 nmol/L, 12.2% at nmol/L | |
| Advia, Centaur, Siemens | S/P 20 μl, buffered releasing agent | CLIA, acridinium-labeled mouse mAb, fluorescein vitamin D analog, anti-fluorescein mAb, PMP 1-anilinonaphthalene-8-sulfonic | Equivalence: Yes 104%/100%, cross-reactivity: 1.1%/NR | Calibrators standardised to ID-LC-/MS/MS, 25OHD RMP; traceable to the NIST SRM 2972, recovery not reported | 10.5(8.0) | 4.7% at 34 nmol/L, 11.9% at 34 nmol/L |
| Architect 1, Abbott | S/P 60 μl, 2 step procedure, EtOH/triethanolamine/ANSA | CLIA, Sheep polyclonal Ab-anti-25OHD, acridinium-labeled biotinylated anti-biotin IgG complex | Equivalence: 82%/100%, cross-reactivity: 2.7%/112% | NR, no mention of traceability, recovery not reported | 20 (7.8) | 3.1% at 58 nmol/L, 4.0% at 58 nmol/L |
| Roche Elecsys, Roche Diagnostics | S/P 15 μl, 2 step procedure, Dithiothreitol pH 5.5, then NaOH | ECL, CBPA, Ruthenium | Equivalence: 92%/100%, cross-reactivity: 91%/149% | Standardized against in house LC-MS/MS standardized to the NIST standard, recovery not reported | 10 (7.5) | 7.8% at 17 nmol/L |
| Vitros 5600, Vitros | S 60 μl, 1 step procedure, acid pH | CLIA, Sheep mcAB-anti-25OHD, Horseradish peroxidase – Luminol | Equivalence: Yes, cross-reactivity: Yes 37.4%/34.3% | In house reference calibrators, Correlation to LC/MS/MS, recovery not reported | 32 (21.6) | 7.4% at 56nmol/L, 14.0% at 56 nmol/L |
| Beckman Dxi, Beckman–Coulter | S/P 30 μl, 1 step procedure, Tris buffered saline | CLIA, Sheep mcAB-anti-25OHD 25OHD, analog AP-conjugate, Lumi-Phos* 530 | Equivalence: Yes, cross-reactivity: 65%/0% | Calibrators standardised to ID-LC-/MS/MS, 25OHD RMP; traceable to the NIST SRM 2972, recovery not reported | 11 (3.7) | 4.6% at 39 nmol/L, 8.1% at 39 nmol/L |
Unless otherwise specified, the characteristics of the commercial assays are derived from the information given in the respective inserts. Recovery refers to the % of the exogenously added 25OHD3 (nmol/L) before extraction recovered at completion of the assay. RIA: radio immnuno assay; EIA: enzyme-linked immuno assay; CLIA: chemi luminescent immuno assay, CBPA: competitive binding-protein assay; ELISA: enzyme-linked immuno sorbent assay; CLIA: chemi luminesent immuno assay; ECL: electro chemiluminescence S: serum; P: plasma; LOQ: lower limit of quantification defined as a measure with a CV<20%; LOD: lower limit of detection defined as the lowest concentration that can be defined with a confidence of 95%; NR: not reported; CV: coefficient of variation at the lowest concentration tested. EtOH: Ethanol; 3H-25OHD2: [23,24(n)-3H]-25-hydroxyvitamin D3 or [26(27)-methyl-3H]-25-hydroxyvitamin D3; 125I-CC: vitamin D-23,24,25,26,27-pentanor-C(22)-carboxylic-amide-3-aminopropyl; ANSA: 8-anilino-1-naphthalene sulfonic acid; IgG: immunoglobulin G; mcAB: monoclonal antibody; BSA: bovine serum albumin; AP: alkaline phosphatase; Lumi-Phos* 530: trademark of Lumigen Inc. (Southfield, MI); ID-LC-/MS/MS: isotope dilution-liquid chromatography/tandem mass spectrometry; RMP: reference method procedure; NIST: National Institute of Standards and Technology; SRM: standard reference material
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