Free and Bioavailable Vitamin D Moderately Predicts Total Vitamin D Status in Tuberculosis Patients and Household contacts

Abstract

Total vitamin D is considered a perfect index for assessment of vitamin D status, attributable to longer half-life. However the bioactive free and bioavailable vitamin D levels are available to the cell. This study aimed to compare and evaluate the accuracy of free and bioavailable vitamin D in defining total vitamin D status in Patients with Tuberculosis. This was a cross-sectional study among newly diagnosed active tuberculosis patients, latent tuberculosis individuals and individuals without TB infection. Total vitamin D was measured by electrochemiluminescence and free and bioavailable vitamin D was measured using ELISA. The diagnostic performance of free and bioavailable portion was 59.18% for sensitivity, 66.67% for specificity, and 63.0% for AUC. The kappa statistic was 1460 (P-value = 0.0759), in the deficient group. In insufficient, sensitivity was,56.9% specificity was 66.7%, and AUC was 61.8%. Kappa was 0.146, P = 0.07. Free and bioavailable vitamin D is a moderate indicator of vitamin D status. The study suggested that free and bioavailable vitamin D is not superior for defining total vitamin D status in TB, however it may be complementary. Further studies are needed to improve the definition of vitamin D status and its importance in immunity.