Vitamin D Deficiency and Latent Tuberculosis Infection Risk among Tuberculosis Household Contacts.

Background: Vitamin D (VD) enhances the immune response against Mycobacterium tuberculosis in vitro, and VD deficiency has been described in patients with clinical tuberculosis (TB). However, the role of hypovitaminosis D in the pathogenesis of early TB infection is unclear. We aimed to evaluate the role of VD deficiency as a risk factor for TB infection in contacts, given that this is a potentially modifiable condition often related to nutritional deficiencies and lack of sun exposure.

 

Methods: A cross-sectional study was conducted among new pulmonary TB cases and their adult household contacts in 19 outpatient clinics in Santiago, Chile. Asymptomatic contacts with normal chest X-ray were enrolled, and screened for latent TB infection (LTBI) with QuantiFERON TB-Gold test. We compared plasma 25-hydroxycholecalciferol (25OHD) levels and inflammatory mediators by multiplex immunoassay. We also examined the influence of M. tuberculosis genotype (by spoligotyping and MIRU-12), ethnic background and country of origin.

 

Results: 251 subjects were enrolled, including 107 TB cases and 144 contacts (25.7% migrants from high TB incidence countries). All enrolled subjects had low median levels of 25OHD, although hypovitaminosis D (<20 ng/ml) was more profound among TB cases than among contacts (11.7 vs 18.7 ng/ml, p<0.0001) (Fig 1). Migrant contacts had higher prevalence of LTBI than non-migrants (56.8% vs 36.4%, p=0.034) as well as lower levels of plasma 25OHD (14.3 vs 19 ng/ml, p=0.012) (Fig 2). On multivariate analysis, the presence of LTBI in contacts was strongly associated with being migrant (OR 2.66, 95%CI 1.16-6.07), male sex (OR 3.06, 95%CI 1.48-6.33) and acid-fast smear intensity in index case (OR 2.86, 95%CI 1.2-6.6). No significant association was found between LTBI and plasma 25OHD levels, high-sensitivity C-reactive protein, IL6, α-TNF or M. tuberculosis genotype.

 

Conclusion: Hypovitaminosis D was highly prevalent among TB cases and their contacts, and particularly accentuated among migrant contacts, which also shared the highest burden of LTBI. However, we found no association between the presence of LTBI and 25OHD levels. Therefore, our findings do not support that VD deficiency confers increased susceptibility to acquire TB infection.