GSTM1 and inflammatory bowel disease: For this reason, they performed a new meta-analysis, using the same studies included by colleagues, and concluded that intravenous iron was more effective than oral ferrous iron in achieving an increase in Hb greater than 2 g/dL in IBD patients (odds ratio (OR): 1.57, 95% confidence interval (CI): 1.13–2.18) [4].