LEP and breast cancer: Similarly, the subgroup analysis by test method suggested significantly higher serum leptin levels in BC cases than the controls in ELISA (SMD = 0.71, 95% CI = 0.51–0.91, P <.0001) or RIA (SMD = 0.32, 95% CI = 0.07–0.57, P = .012) (Fig. 3).