GSTM1 and Arthritis: The prediction model for autoimmune diseases compared with infections used the following equation: − 1.5 + (3.5 × arthritis) + (1.3 × duration of fever 15–30 days) + (2.3 × duration of fever > 30 days) + (− 1.9 × cough) + (0.8 × splenomegaly) + (0.4 × lymphadenopathy) + (0.8 × Hb < 7 g/dL) + (− 0.1 × platelet count < 150,000 cells/mm3).