Serum calcitriol concentrations measured with a new direct automated assay in a large population of adult healthy subjects and in various clinical situations

The mean calcitriol concentration (± SD) in the healthy population was 52.9 ± 14.5 ng/L with a 95% CI interval of 29-83.6 ng/L. In PHPT patients, calcitriol concentration was 81.6 ± 29.0 ng/L, 15 of them (46.9%) having a concentration > 83.6 ng/L. In pregnant women, calcitriol was 80.4 ± 26.4 ng/L at the end of the first trimester, and 113.1 ± 33.0 ng/L at the end of the third trimester, 12 (37.5%) and 26 (81.3%) of them having a calcitriol concentration > 83.6 ng/L at the first and third trimesters respectively. In 14 dialysis patients, calcitriol was 9.5 ± 7.7 ng/L and rose to 19.3 ng/L after one year of supplementation with 50,000 IU vitamin D3/month. In 10 other dialysis patients, calcitriol was 9.9 ± 2.9 ng/L and remained stable (12.4 ± 3.7 ng/L) after one year of placebo. In conclusion, this new automated calcitriol assay, in addition to presenting excellent analytical performances, gives the expected variations in patients compared to “normal” values obtained in an extensive reference population.