On the other hand, when combining the very few results on GSTM1 and GSTT1 (Table 3), a significant heterogeneity in frequencies of the null genotype distribution in IBD patients was reported (GSTM1 test for heterogeneity: Q = 28.95; DF = 2; I2 = 93.1%; P < 0.0001; GSTT1 test for heterogeneity: Q = 61.47; DF = 2; I2 = 97%; P < 0.0001). Here, GSTM1 is linked to inflammatory bowel disease.