A univariate analysis showed that use of co-trimoxazole prophylaxis therapy, CD4 count < 200cells /μl, presence of anemia and presence of lymphopenia were associated with increased risk of leucopenia with OR 3.06(IC 95% 1.43-6.55; p = 0.005), OR 5.54(IC 95% 2.87-10.7; p = 0.000), OR 2.78(IC 95% 1.41-5.48; p = 0.004) and OR 6.23(IC 95% 2.32-16.74; p = 0.000), respectively. The gene discussed is CD4; the disease is anemia (phenotype).