Challenges for retrospective cohort studies: A profile of patients who refuse participation or are lost to follow-up

6615 Background: As hematopoietic cell transplantation (HCT) has increasingly become a curative option for many diseases, studying long-term complications has assumed critical importance. A major issue in conducting scientifically rigorous long-term follow up studies with large cohorts is the ability to track patients, and obtain informed consents. High participation rates are critical to avoid selection bias and ensure generalizability. Methods: A mass consenting process was implemented to obtain informed consents from 1056 City of Hope HCT patients transplanted during 1976–2006 who were one+ year survivors and alive in June 2007. This process involved mailing consent forms followed by phone calls. Patients were classified as consented, refused, or lost-to-follow-up (LTFU). Sociodemographic and clinical characteristics indicative of higher risks for refusal or LTFU were identified. Results: Study patients comprised 58% males, and 53% Caucasians. Median age at HCT was 34 years (0.6–73); median age at study initiation was 47 years (6–81); and median time from HCT to study initiation was 10 years (1–30). Primary diagnoses included acute/chronic leukemia (43%), Hodgkin/non-Hodgkin lymphoma (36%), multiple myeloma (9%), and other miscellaneous diagnoses (12%). Fifty percent received allogeneic HCT. At the end of the process, 46% consented, 17% refused, and 37% were LTFU. Compared to consented patients, males, Asians, and younger patients were more likely to refuse consent. Patients LTFU were more likely to have lower SES, a longer time since HCT, in addition to being males, Asians and younger at HCT (Table). Conclusions: This study demonstrates the critical need for maintaining up-to-date contact information on patients after HCT in order to obtain valid long-term follow-up data. It also describes the characteristics of the sub-population that are more likely to refuse or be LTFU, information necessary for planning targeted interventions in long-term follow-up initiatives. [Table: see text] No significant financial relationships to disclose.