Hypoxia inducible factor prolyl hydroxylase inhibitors: what a meta-analysis could tell us

Meta-analyses offer an estimate of the overall effect size and help address the inconsistency in findings across studies. The risk is the overemphasis on statistical significance while underrepresenting or misinterpreting clinical significance. There's also a lack of standardized methods for quantifying and reporting clinical significance and these measures are often missing or inconsistently reported in many meta-analyses, making it difficult for readers to determine the clinical relevance of the findings. A major merit of Minutolo's meta-analysis is to formally evaluate efficacy and safety of Hypoxia Inducible Factor Prolyl Hydroxylase Inhibitors (HIF-PHI) as class and as single agents in comparison with ESA, by selecting from only phase-3 randomised clinical trials (RCTs) that compared HIF-PHIs with erythropoiesis-stimulating agents (ESAs) in dialysis and non-dialysis patients. From a clinical perspective, the primary evaluation in this meta-analysis should have been the percentage of patients able to reach and maintain the target haemoglobin (Hb) levels throughout the trials but only a few RCTs selected this primary end point. Any claimed superiority of one drug over another should consider the selected doses. The amount of iron administered to patients, their iron stores and level of inflammation are important confounding factors that affect the reliability of any comparison.