Multi‐centre validation of the prognostic value of the haematopoietic cell transplantation‐ specific comorbidity index among recipient of allogeneic haematopoietic cell transplantation

The haematopoietic cell transplantation-specific comorbidity index (HCT-CI) was developed in a single centre as a weighted scoring system to predict risks of non-relapse mortality (NRM) following allogeneic haematopoietic cell transplantation. Information on the performance of the HCT-CI in multi-centre studies is lacking in the literature. To that end, a collaborative multicentre retrospective study was initiated. Comorbidity data from 2523 consecutive recipients of human leucocyte antigen-matched grafts from five different US institutions were analysed. Among all patients, HCT-CI scores of 0 vs. 1-2 vs. ≥3 were associated with 2-year NRM rates of 14%, 23% and 39% (P < 0·0001), respectively, and 2-year overall survival (OS) rates of 74%, 61% and 39%, respectively (P < 0·0001). Using regression models, increasing HCT-CI scores were independently associated with increases in hazard ratios for NRM and worse survival within individual institutions. The HCT-CI retained independent capacity for association with outcomes within different age as well as conditioning intensity groups. C-statistic estimates for the prognostic power of the HCT-CI for NRM and OS were 0·66 and 0·64, respectively. The estimates within each institution were overall similar. The HCT-CI is a valid tool for capturing comorbidities and predicting mortality after haematopoietic cell transplantation across different institutions.