CXCL8 and central nervous system cancer: Based on the methodological subgroup analysis (Table 3), patients with glioma detected using other methods (pooled SMD 0.66 [95% CI: 0.39‐0.92; P = .000]) but not ELISA (pooled SMD 1.31 [95% CI: −0.45‐3.08; P = .144]) had significantly elevated levels of IL‐8.