Medición de 25-hidroxivitamina D sérica: comparación de dos inmunoensayos

serum concentration of 25-hydroxyvitamin d (25ohd) is used as an indicator of nutritional status of vitamin d (vd). the methodolgy more frequently used for its measurement is ria. the recent development of automated non-radioactive methodologies would help the laboratory daily practice to diagnose the need for supplementation. objectives: to compare the data of 25-ohd obtained using a ria and an automated chemiluminescence method (clia) automated available in our country. materials and methods: concentrations of 25-ohd were measured in serum of 45 patients: 8 men and 37 women, 18 unsupplemented and 27 supplemented with vd (n=5 with vd2 and n=22 with vd3). for 25-ohd measurements we used a ria and a qlia under an automated platform (liaison), both diasorin. we calculated intra-assay (intra) and interassay (inter) coefficients of variation (cv%) for both methods. statistical analysis: comparison between methods was conducted with analyse-it and med calc softwares; p <0.05 was considered significant. results: the intra and inter cv% were below 19.9 and 10.6 for ria vs 8.0 and 13.2 for clia, respectively. in the overall population and in the subgroup never supplemented with vd, data for ria vs clia were: pearson correlation coefficient (0.9259 vs 0.9412), bias% (6.1 vs. 2.7), concordance coefficient (0.9244 vs 0.9329). conclusions: 1) both methods are suitable for measurements of 25ohd, particularly in cases not medicated with vd, 2) the trend toward greater bias% observed in patients supplemented with vd does not appear to be attributable to methodological variability, and suggests that exogenous vd or its metabolites interact differently in the measurement of 25-ohd by each of the methodologies used. a higher number of cases is needed to confirm this hypothesis.