Among the 17 studies included in our review, the gender, advanced age, low peripheral lymphocyte counts (including CD4+ T lymphocytes), HIV positivity, extrapulmonary TB and body mass index (BMI) were studied using a multivariate analysis in 3, 14, 7, 4, 5 and 3 studies, respectively (Fig. 1). The gene discussed is CD4; the disease is tuberculosis.