Serum 25-hydroxyvitamin D in a West African population of tuberculosis patients and unmatched healthy controls

Abstract

Background: Little is known regarding vitamin D deficiency (VDD) in African populations and in tuberculosis (TB) patients. VDD has been shown to be associated with TB.Objective: We aimed to compare the degree of vitamin D insufficiency (VDI) and VDD in TB patients and healthy adult controls in a West African population.Design: An unmatched case-control study was performed at a Demographic Surveillance Site in Guinea-Bissau. Serum 25-hydroxyvitamin D3 [25(OH)D3] concentrations were measured in 362 TB patients and in 494 controls.Results: Hypovitaminosis D [25(OH)D3 ≤ 75 nmol/L] was more common in TB patients, but VDD [25(OH)D3 ≤ 50 nmol/L] was more common and more severe in controls. We observed hypovitaminosis D in 46% (167/362) of the TB patients and in 39% (193/494) of the controls; the relative risk (RR) of hypovitaminosis D was 1.18 (95% CI: 1.01, 1.38). VDD was observed in 8.5% (31/362) of the TB patients and in 13.2% (65/494) of the controls. The RR was 0.65 (95% CI: 0.43, 0.98), mainly because severe VDD [25(OH)D3 ≤ 25 nmol/L] was observed in only 1 of 362 TB patients (0.2%) and in 24 of 494 controls (4.9%). After adjustment for background factors, hypovitaminosis D was not more frequent in TB patients than in healthy controls, but the mean serum 25(OH)D3 concentration remained lower.Conclusions: Hypovitaminosis D was highly prevalent in TB patients and in healthy controls living at 12 °N; severe VDD was rare in TB patients. The finding indicates that the serum 25(OH)D3 concentration is associated with TB infection, but whether this role is a symptom or is causal was not established.