They were more likely to have advanced immunodeficiency (CD4 T-cell count < 100 cells/mm3) (P = 0.003), a history of hazardous alcohol use (P < 0.001), a body mass index < 18 kg/m2 (P = 0.03) or a haemoglobin level < 10 g/dL (P = 0.02) (Table 1). This evidence concerns the gene CD4 and immune system disorder.