Vitamin D status and latent tuberculosis infection: conversion in nursing homes, Spain.

OBJECTIVE: To examine the potential association between vitamin D (VitD) deficiency and latent tuberculosis infection (LTBI) and its effect on TB infection conversion (TBIC) incidence.MATERIAL AND METHODS: We carried out a cross-sectional and prospective cohort study of nine pulmonary TB cases that occurred in 2015-2016 in five nursing homes and one mental disability institution in Castellon, Spain. QuantiFERON®-TB Gold and the tuberculin skin test were used to detect LTBI and TBIC, respectively. Serum 25-hydroxyvitamin D was measured using chemiluminescence immunoassay. Poisson regression and inverse probability weighting were used for statistical analyses.RESULTS: The study included 448 residents, 341 staff members with 48 relatives of TB cases (participation rate 82%): of these, respectively 122 (27.2%), 37 (10.9%) and 7 (14.6%) were LTBI-positive; and respectively 22 (7.7%), 10 (3.8%) and 1 (3.7%) were TBIC-positive. LTBI was not associated with VitD status. Severe VitD deficiency (SVDD; defined as VitD level < 10 ng/ml), found in 45.1% of residents, as well as VitD levels of <30 ng/ml (aRR 10.41 95% CI 1.48-73.26), were associated with increased TBIC risk (adjusted relative risk [aRR] 12.1, 95% CI 1.51-97.10), suggesting SVDD as a threshold effect. CONCLUSION: Severe VitD deficiency is a TBIC risk factor.

Vitamin D status and incidence of tuberculosis infection conversion in contacts of pulmonary tuberculosis patients: a prospective cohort study.

The objective of this study was to estimate the relationship between serum vitamin D (VitD) status and tuberculosis (TB) infection conversion (TBIC), measured by the tuberculin skin test (TST) and an interferon-gamma release assay, the QuantiFERON-TB Gold In-Tube (QFT-GIT) test, in the contacts of pulmonary TB patients in Castellon (Spain) in a prospective cohort study from 2010 to 2012. Initially, the participants were negative to latent TB infection after a screening that included TST and QFT-GIT tests, and other examinations. A baseline determination of 25-hydroxyvitamin D [25(OH)D] was obtained by chemiluminescence immunoassay. After 8-10 weeks, participants were screened for a second time to determine TB infection conversion (TBIC). Poisson regression models were used in the statistical analysis. Of the 247 participants in the cohort, 198 (80·2%) were screened twice and 18 (9·1%) were TBIC cases. The means of VitD concentration in the TBIC cases and the non-cases were 20·7±11·9 and 27·2±11·4 ng/ml (P = 0·028), respectively. Adjusted for high exposure and TB sputum acid-fast bacilli (AFB)-positive index case, higher serum VitD concentration was associated with low incidence of TBIC (P trend = 0·005), and an increase of 1 ng/ml VitD concentration decreased the incidence of TBIC by 6% (relative risk 0·94, 95% confidence interval 0·90-0·99, P = 0·015). The results suggest that sufficient VitD level could be a protective factor of TBIC.

Vitamin D status and incidence of tuberculosis among contacts of pulmonary tuberculosis patients.

A prospective cohort study was conducted from 2009 to 2012 to assess the relationship between serum baseline 25-hydroxivytamin D (vitamin D) status and the incidence of tuberculosis (TB) among 572 contacts of 89 pulmonary TB patients in Castellon, Spain. Three new cases of pulmonary TB occurred, with an incidence density of 3.6 per 1000 person-years. Mean vitamin D status was 13.7 ng/ml for cases and 25.7 ng/ml for non-cases. Vitamin D status showed a significant inverse association with TB incidence (adjusted HR 0.88, 95%CI 0.80-0.97). This result is in line with the hypothesis that vitamin D deficiency is associated with TB incidence.