Medication Adherence in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: Medication adherence is essential for treatment and recovery following hematopoietic stem cell transplantation (HSCT). However, limited data exist on the most effective methods to measure adherence and the factors influencing it in HSCT patients. Materials and Methods: A prospective longitudinal study assessed immunosuppressant medication adherence in 150 patients with hematologic malignancies undergoing allogeneic HSCT. Adherence was assessed using pill counts, immunosuppressant medication levels, patient-reported medication logs, and the Medication Adherence Response Scale-5 (MARS-5) at 30, 100, and 180 days post-HSCT. We evaluated adherence rates, agreement between methods, and sociodemographic and clinical predictors. From patient-reported logs, we calculated dose adherence (comparing reported doses to expected doses) and timing adherence (comparing medication intake within ±3 h of the prescribed time). Kappa analysis assessed agreement among methods. Results: Of 190 eligible patients, 150 (78.9%) enrolled. The mean age was 57.5 years (SD = 13.5); 41.3% (n = 62) were female, 85.3% (n = 128) were non-Hispanic White, and 73.3% (n = 110) were married or living with a partner. Medication adherence varied across the three timepoints and by measurement type: 52-64% (pill counts), 18-24% (medication levels), 96-98% (medication log dose adherence), 83-84% (medication log timing adherence), and 97-98% (MARS-5). There was minimal agreement between measures (Kappa range: 0.008-0.12). Conclusions: Despite the feasibility of leveraging objective and patient-reported measures to assess medication adherence in HSCT patients, there was little agreement between these measures. Patient-reported measures showed high adherence, while objective measures like pill counts and medication levels revealed more modest adherence. The complexity of medication regimens likely contributes to this discrepancy. A rigorous approach to understanding medication adherence in the HSCT population may entail both objective and subjective measures of medication adherence.