EP228 - ECE_2697 - Analytical performance of the automated ionify vitamin D LC-MS/MS assay for the quantification of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D
Year: 2026
Type: conference-abstract
Abstract: Introduction Measurement of 25-hydroxyvitamin D [25(OH)D] is clinically important because both elevated and deficient levels are associated with disturbances in calcium and phosphorus homeostasis. The metabolite 25-hydroxyvitamin D [25(OH)D] serves as the primary clinical biomarker for establishing vitamin D sufficiency. Beyond total 25(OH)D, the measurement of 24,25-dihydroxyvitamin D [24,25(OH)2D] has gained clinical relevance for identifying patients with CYP24A1 gene mutations and overcoming limitations associated with fixed 25(OH)D cutoffs. Consensus statements highlight the important role of vitamin D metabolites, in particular of the 24,25 to 25(OH)D ratio. Although LC-MS/MS offers superior specificity, its routine use is often limited by the need for specialized staff and complex manual workflows. This study evaluated the analytical performance of the Ionify® Vitamin D iPack on the Cobas® i 601 analyzer, a fully automated LC-MS/MS system. Methods Repeatability and reproducibility (CLSI EP05-A3) were assessed across three laboratories using three reagent lots over five days. Inter-laboratory accuracy was evaluated at six sites using External Quality Assessment (EQA) samples (DEQAS, CAP) compared to Reference Measurement Procedures (RMPs). Additionally, a method comparison (CLSI EP09c) was performed against a validated in-house LC-MS/MS Laboratory Developed Test (LDT) using patient serum samples. Results The assay demonstrated robust precision across all sites and reagent lots. Coefficients of variation (%CV) for repeatability and reproducibility (lot-to-lot and site-to-site) ranged from 2.7%-4.8% for 25(OH)D and 2.3%-3.5% for 24,25(OH)2D, with nearly all %CVs remaining below 6%. Accuracy assessment revealed median recoveries ranging from 89% to 110% of expected values and 92%-109% of the reference method values. Method comparison showed high correlation with the validated LDT for both metabolites (Pearson r: 0.984-0.995; slopes: 0.913-1.027). The test duration for one sample on the system for the tested analytes was 34 minutes, respectively. Conclusions The Ionify Vitamin D assay on the Cobas i 601 analyzer provides precise, accurate, and reproducible measurements of 25(OH)D and 24,25(OH)2D. By combining the analytical superiority of LC-MS/MS with full automation, this system supports timely and accurate measurements of vitamin D metabolites in routine laboratory settings.
Language: English
Topic: Vitamin D Research Studies
Subfield: Pathology and Forensic Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,292
OpenAlex ID: W7213345250
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