MSACL 2023 Abstract

Background:
Accurate measurement of 25-OH vitamin D(25-OH-D) is important for vitamin D status monitoring. Although Isotope dilution liquid chromatography mass spectrometry (ID-LC-MS/MS) is confirmed as reference measurement procedure, many laboratories or researchers still use immunoassays because of the convenience and availability, regardless of standardization. In present study, authors evaluated the clinical performance of mass spectrometry and immunoassay for 25-OH-D measurement.

Method:
The accuracy of MS tests was evaluated by measuring standard reference material produced by National Institute of Standards and Technology (NIST SRM 972a). Then, using the mean values from two laboratory-developed test (LDT) mass spectrometrys (MS) for vitamin D as standard, the qualitative decision concordance and quantitative correlation with another LDT MS test and four commercialized immunoassays; Roche Elecsys Vitamin D Total II, Siemens Atellica IM Vitamin D Total assay, Abbott Alinity 25-OH Vitamin D, and Beckman Coulter Access 25-OH Vitamin D Total, were evaluated for 150 residual serum samples.

Results:
In accuracy, it was confirmed that the mean values obtained from MS tests for standard materials were within the range of assigned value. When the measured 25-OH-D values from each assay were compared to those determined by MS, ranged 5.86-67.75 ng/ml, In contrary to the equivalence between two MS tests with regression slope and intercept those containing 1 and 0 in their 95% confidence interval (CI) and r2 larger than 0.95, none of the immunoassays was equivalent to MS, by showing slope or intercept not containing 1 and 0 in their 95% CI, r2 smaller than 0.95. The regression estimates at 10, 20, and 30 ng/ml as medical decision limit (MDL) were within 5.0% the Vitamin D Standardization-Certification program (VDSCP)-claimed acceptable bias limit, in Beckman test at 30 ng/ml, only. The concordance of qualitative decision with MS ranged 90.0-94.0% in immunoassays.

Conclusion:
It was revealed that the two MS showed good qualitative decision agreement and quantitative correlation. However, despite having been achieved the certification by VDSCP, most immunoassays showed difference over acceptance criteria in the 25-OH-D measurement at MDL levels, which may affect clinical decision-making. Therefore, the superiority of MS test in measuring 25-OH-D compared to immunoassay has confirmed by this study, and attention for results interpretation and efforts for test standardization is required for immunoassays.