Extended RBC phenotype matching reduces the incidence of alloimmunisation in patients with warm autoimmune haemolytic anaemia (wAIHA)

Background: Warm autoimmune haemolytic anaemia (wAIHA) involves autoantibodies destroying red blood cells, often necessitating transfusions. Alloimmunisation, the formation of antibodies against non-self RBC antigens, complicates future transfusions. This review evaluates whether extended RBC phenotype matching reduces alloimmunisation compared to standard ABO and Rh matching.\nMethods: Databases (PubMed, Scopus, Cochrane Library and Google Scholar) were searched for studies (2014–2024) on wAIHA patients comparing basic, partial, and full extended RBC phenotype matching. Eligible data were analysed using a random-effects model to assess alloimmunisation risk reduction. Manual searches were performed using relevant references. \nResults: Ten studies, both retrospective and prospective, were included. Basic matching (ABO and Rh) had the highest alloimmunisation rate at 32.8% (95% CI, 13.3%–52.2%; I² = 95.79%, p < 0.001). Partial matching (Rh and Kell) reduced rates to 22.5% (95% CI, 10.4%–34.6%; I² = 49.57%, p = 0.046), while full matching lowered it to 11.6% (95% CI, 4.5%–18.7%; I² = 73.65%, p = 0.001). Despite heterogeneity, results consistently showed extended matching reduced alloimmunisation.\nConclusion: Extended RBC phenotype matching significantly lowers alloimmunisation risk in wAIHA patients, particularly in chronically transfused cases. However, the variability across studies highlights the need for standardised transfusion practices and further research to confirm these results through larger, randomised controlled trials.<p></p>