The effect of HLA matching and donor relatedness on the risk of autoimmune haemolytic anaemia in haematopoietic stem cell transplant recipients: A systematic review and meta‐analysis

Recent studies have identified autoimmune haemolytic anaemia (AIHA) as a haematopoietic stem cell transplant (HSCT) complication that represents a significant cause of morbidity and mortality for these patients. In order to understand this autoimmune phenomenon, emerging research has focused on the prognostic factors associated with the development of the disorder. These studies have identified numerous possible associations with often contrasting and conflicting results. A systematic review and meta‐analysis were performed in order to determine the effect of human leucocyte antigen (HLA) matching and donor relatedness on the risk of AIHA post‐HSCT. PubMed, SCOPUS and ProQuest were searched from 1 January 1995 to 1 August 2021 using a range of keywords. Meta‐analysis was performed using OpenMeta‐Analyst software using a random effects model and arcsine risk difference (ARD). Eight eligible articles were identified, and meta‐analysis showed an increased risk of AIHA in those who received HLA‐mismatched transplants (ARD −0.082; 95% confidence interval [CI] −0.157, −0.007; p = 0.031) and those who received donations from unrelated donor sources (ARD −0.097; 95% CI −0.144, −0.051; p < 0.001). Patients who receive HSCT from HLA‐matched and related donor sources have a reduced risk of developing AIHA. Healthcare practitioners should be mindful of the risk of AIHA, especially in those who receive HLA‐mismatched and unrelated donor‐sourced stem cells. While these findings provide further evidence for researchers investigating the pathogenesis of this HSCT complication, more studies are needed to fully understand the cause.