Serum selenium levels in tuberculosis patients: A systematic review and meta-analysis

Introduction: Tuberculosis (TB) is associated with increased mortality. The high risk of micronutrients deficiency, including selenium, in TB patients is of great concern because it increases the risk of death. However, it is not clear whether selenium supplementation could improve the treatment outcomes in TB patients. We conducted a systematic review and meta-analysis to provide an update on the existing evidence about low selenium levels in TB patients. Methods: In this systematic review and meta-analysis, EMBASE, Medline and the International Journal of Tuberculosis and Lung Disease were searched to identify observational studies on selenium and TB published up until April 2018. Studies comparing blood selenium levels in TB patients to controls were included. Data extraction was performed by two investigators. The quality of the studies was assessed using the Newcastle-Ottawa Quality Assessment Scale. Random effects analysis was performed to calculate the pooled effect size and 95% confidence interval (CI). Results: Of the 605 studies initially identified, only six were eligible. Of them, four were carried out in Asia, and one each in Africa and South America. The random pooled effect size was 1.6 (CI: 0.9, 2.4). This means that the probability is 160% for an individual with TB to have low levels of selenium as compared to an individual without TB. Heterogeneity across the studies was substantial (I² = 95.1%). Potential sources of heterogeneity included study design and selenium measurement methods. Conclusion: Our review provides compelling evidence that serum selenium is lower in TB patients as compared with controls. Therefore, it is advisable to individually assess selenium status in TB patients and decide whether selenium supplement is needed or not.