Abstract

BASILOTTA, N et al. Comparison of Three Methods for 25 Hydroxyvitamin D Measurement in Patients with No Supplementation or Supplemented with Ergocalciferol, Cholecalciferol or Both. Rev. argent. endocrinol. metab. [online]. 2014, vol.51, n.1, pp.15-24. ISSN 1851-3034.

Introduction: There are several methodological options for 25 hydroxyvitamin D (25OHD) measurement. The lack of standardization across methods can lead to discrepant results, which could be accentuated in the case of patients supplemented with different forms of vitamin D. Objective: To compare three methods for 25OHD quantification and to compare the 25OHD results from untreated subjects with those obtained from subjects receiving ergocalciferol (D2), cholecalciferol (D3), or both. Materials and Methods: We analyzed 82 samples by QLIA of Abbott Diagnostics (Architect i1000), EQLIA Roche Diagnostics (Cobas 601) and RIA DiaSorin. Samples were divided into four groups: G1: untreated; G2: treated with D2, G3 treated with D3 and G4: treated with D2 + D3. Results: Considering all samples, there was a significant difference between mean 25OHD results obtained by the three methods (F: 14.80, p < 0.0001), being similar with RIA and EQLIA but lower with QLIA (p < 0.05). In the four groups studied, RIA and EQLIA results were similar in the presence or absence of treatment. In G2, there was a significant trend to lower levels with QLIA, compared to the other two methods (p = 0.0003), and the same trend was observed in G4 (p < 0.02). This difference in G3, albeit significant (p < 0.05), was less marked. Bland and Altman showed that QLIA underestimated the measured concentrations compared with EQLIA, average ? RIA: - 5.69 to - 14 ng/mL). This was not observed when comparing EQLIA vs. RIA (?: - 3.45 to 0.47 ng/mL). Conclusions: There are methodological differences in the design and specificity of immunoassays, which recognize 25OHD and its metabolites in different proportions. Therefore, patients might be classified as 25OHD sufficient or insufficient depending on the methodology used. Results suggest that RIA and EQLIA measurements are comparable in untreated patients and in patients treated with vitamin D2, D3 or both. Rev Argent Endocrinol Metab 51:15-24, 2014 No financial conflicts of interest exist.

Keywords : Vitamin D; 25 (OH) cholecalciferol; Immunoassays.

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