Vitamin D deficiency and its associated factors in active TB patients at a tertiary hospital and three primary health care level facilities in Lusaka, Zambia: A cross sectional analytical study

Background: Tuberculosis (TB) remains a leading infectious cause of morbidity and mortality in Zambia. Vitamin D deficiency has been associated with increased TB incidence and severity but data for the Zambian setting is lacking, inclusive of the general population. We sought to determine the prevalence of vitamin D deficiency and its associated factors in active TB patients in comparison to matched adults from the general population without TB, and to compare clinical and radiological severity of TB based on vitamin D status. Methods: We enrolled 89 TB patients and 78 matched adults from the general population. Demographic and clinical data was collected. The key findings on physical examination were body mass index (BMI), mid upper arm circumference (MUAC), and signs of undernutrition. Clinical severity was assessed using the TB I Score and the Karnofsky Performance Index (KPI).Chest x-ray  and measurement of serum vitamin D levels  were done. Radiological severity was assessed using the Timika chest x-ray score. Vitamin D was measured using the Cobas® E411 analyser from Roche Diagnostics (Germany) with vitamin D deficiency defined as <30 ng/ml and chi square used to analyse vitamin D deficiency as a categorical variable. Results: The median (IQR) age was 27.5 (24-38) years in the TB patients and 32 (25-37)  years in the non-TB adults (p=0.30).Sixty-nine (77.53%) of the TB patients and 57 (73.08%) of the comparison group were male (p=0.51). The prevalence of vitamin D deficiency was 33.71 % in the TB patients and 15.38% in the comparison group (p <0.01). Associations with vitamin D deficiency were active TB (AOR =2.27; 95% CI = 1.04- 4.95; p=0.04) and undernutrition (AOR 14.5; 95% CI 1.65-126.97; p=0.02). Median (IQR) KPI was 70 (60-80) in the vitamin D deficient patients compared to 80 (70-90) in non- vitamin D deficient patients (p=0.01). Median (IQR) Timika chest x-ray score was 75 (45-115) in the vitamin D deficient TB patients compared to 42.5 (20-75) in the non- vitamin D deficient patients (p<0.01). Conclusions: We found a significant difference in the prevalence of vitamin D deficiency in active TB patients compared with matched non-TB adults. Vitamin D deficiency was associated with active TB and under nutrition. TB patients with vitamin D deficiency had more clinical and radiological severe disease than those with normal vitamin D levels. These findings warrant further studies on the role of vitamin D supplementation in TB in Zambia.