DEFINING IRON DEFICIENCY IN RCTS: META-ANALYSIS OF THE TREATMENT EFFECT OF IV IRON

Introduction: Iron deficiency (ID) is a common cause of anaemia. However, there is variability in the definition of ID. We explore the effect of IV iron based on the different definitions of ID.

Methods: We updated the Cochrane review that evaluated iron therapy in patients with anaemia from inception to July 2020. The primary outcome was a change in haemoglobin (Hb). Iron status were defined as: Absolute ID (AID): Ferritin < 30 ng/ml, Functional ID (FID): Ferritin > 30ng/ml or <300 ng/ml or TSAT <20% or Anaemia: no iron studies.

Results: 56 RCTs (8104 participants) were included in the meta-analysis. 26 compared IV to oral iron. 30 studies investigated IV iron. 2 studies were AID, 31 studies were FID and 23 were Anaemia. IV iron was associated with increased change in Hb (MD 0.48 (95% CI 0.06 to 0.9) and an increase in final Hb (MD: 0.85 g/dL; 95% CI, 0.34 to 1.37 g/dL; I2 = 84%) compared to oral iron. IV iron was associated with increased change in Hb (MD: 3.17 (95% CI -2.02 to 8.37) and increased in final Hb (MD: 1.21 g/dL; 95% CI, 0.15 to 2.28 g/dL; I2 =97%) and compared to placebo or no iron. Subgroup analysis by iron status did not delineate the heterogeneity.

Conclusions: There is variation in the definitions of ID used for inclusion. Further research into the dynamic nature of iron metabolism in different clinical populations would allow for more reliable interpretation of trial results.