P02.141 LB
Purpose: Vitamin D insufficiency, serum 25(OH)D ≤ 30 ng/mL, is becoming a more commonly ordered preventative screening measure in clinical care. The study is a comparative analysis of two analytical methods for the analysis of serum 25(OH)D: 1) DiaSorin radioimmunoassay (RIA), and 2) tandem mass spectrometry (LC-MS/MS). The aim of this study is to determine the correlation of the results from the two methods and to report the proportion of reclassification of 25(OH)D insufficiency status.
Methods: Serum 25(OH)D was measured in blood samples from study subjects (N=109) participating in a comparative effectiveness trial of vitamin D supplementation to correct vitamin D insufficiency. Serum 25(OH)D was measured using both the RIA and tandem mass spectrometry (LC-MS/MS). The 25(OH)D (ng/mL) levels are reported as mean (SD) and paired t-test was used to assess between group differences in 25(OH)D. Correlation is reported as Pearson's correlation coefficient. Fisher's exact test was used to determine the odds ratio (OR) of reclassification.
Results: The data showed mean 25(OH)D levels 43.0 (24.3) using RIA, and 41.3 (17.9) using LC-MS/MS, which were not significantly different between groups, p>0.05. From the analyses, 35% were 25(OH)D sufficient using RIA and 27.5% suing LC-MS/MS. With 2.8% being reclassified as sufficient and 10.1% as insufficient, the likelihood of reclassification of 25(OH)D status was OR 67.1, 95%CI 17.6 to 256.2, p<0.001, comparing RIA to LC-MS/MS. A strong correlation was observed between the results using RIA to LC-MS/MS analytical methods (Pearson's r: 0.78, 95%CI 0.70 to 0.85, p<0.0001).
Conclusion: These results show a significant correlation between the RIA and LC-MS/MS methods, suggesting that the LC-MS/MS and RIA analytical methods are comparable. However, there is a high likelihood of reclassification of vitamin D status between methods. Care should be taken in interpreting clinical and study results using different analytical methodologies for the determination of serum 25(OH)D.
Contact: John Finnell, jfinnell@aoma.edu
