Financial Incentives to Increase Stool Collection Rates for Microbiome Studies in Adult Bone Marrow Transplant Patients

Introduction In order to learn more about the role of the microbiome in hematopoietic stem cell transplantation (HCT), researchers collect stool samples from patients at various time points throughout HCT. However, unlike blood samples or skin swabs, stool collection requires active subject participation, particularly in the outpatient setting, and may be limited by patient aversion to handling stool. Objectives By providing study participants with compensation for their stool samples, we hypothesize that we can significantly increase stool collection rates. Methods We performed a prospective cohort study on the impact of financial incentives on stool collection rates for microbiome studies. The intervention group consisted of allo-HCT patients from 05/2017-05/2018 who were compensated with a $10 gas gift card for each stool sample. The intervention group was compared to a historical control group consisting of allo-HCT patients from 11/2016-05/2017 who provided stool samples before the incentive was implemented. To control for potential changes in collections over time, we also compared a contemporaneous control group of auto-HCT patients from 05/2017-05/2018 with a historical control group of auto-HCT patients from 11/2016-05/2017; neither auto-HCT groups were compensated. Allo-HCT patients were required to give samples at pre-HCT, day 0 (the day of HCT), and days 7, 14, 21, 30, 60, and 90 post-HCT. Auto-HCT patients were required to give samples at pre-HCT and days 7, 14, and 90 post-HCT. Collection rates were defined as the number of samples provided divided by the number of time points for which we attempted to obtain samples. Results There were 35 allo-HCT patients in the intervention group, 19 allo-HCT patients in the historical control group, 142 auto-HCT patients in the contemporaneous control group, and 75 auto-HCT patients in the historical control group. Allo-HCT patients in the intervention group had significantly higher average overall collection rates when compared to the historical control group allo-HCT patients (80% vs 37%, p Conclusion Our results demonstrate that even a modest incentive can significantly increase collection rates. While this study uses a specialized HCT patient population, these results may be generalizable to informing the design of future studies and aid other researchers in obtaining stool samples needed for future microbiome studies.