Financial incentives to increase stool collection rates for microbiome studies in adult bone marrow transplant patients

Introduction In order to study the role of the microbiome in hematopoietic stem cell transplantation (HCT), researchers collect stool samples from patients at various time points throughout HCT. However, stool collection requires active subject participation and may be limited by patient reluctance to handling stool. Methods We performed a prospective study on the impact of financial incentives on stool collection rates. The intervention group consisted of allogeneic 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 of allogeneic HCT patients from 11/2016-05/2017 who provided stool samples before the incentive was implemented. To control for possible changes in collections over time, we also compared a contemporaneous control group of autologous HCT patients from 05/2017-05/2018 with a historical control group of autologous HCT patients from 11/2016-05/2017; neither autologous HCT group was compensated. The collection rate was defined as the number of samples provided divided by the number of time points we attempted to obtain stool. Results There were 35 allogeneic HCT patients in the intervention group, 19 allogeneic HCT patients in the historical control group, 142 autologous HCT patients in the contemporaneous control group (that did not receive a financial incentive), and 75 autologous HCT patients in the historical control group. Allogeneic HCT patients in the intervention group had significantly higher average overall collection rates when compared to the historical control group allogeneic HCT patients (80% vs 37%, p<0.0001). There were no significant differences in overall average collection rates between the autologous HCT patients in the contemporaneous control and historical control groups (36% vs 32%, p = 0.2760). Conclusion Our results demonstrate that a modest incentive can significantly increase collection rates. These results may help to inform the design of future studies involving stool collection.

Introduction: In order to study the role of the microbiome in hematopoietic stem cell transplantation (HCT), researchers collect stool samples from patients at various time points throughout HCT. However, stool collection requires active subject participation and may be limited by patient reluctance to handling stool. Methods : We performed a prospective study on the impact of financial incentives on stool collection rates. The intervention group consisted of allogeneic 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 of allogeneic HCT patients from 11/2016-05/2017 who provided stool samples before the incentive was implemented. To control for possible changes in collections over time, we also compared a contemporaneous control group of autologous HCT patients from 05/2017-05/2018 with a historical control group of autologous HCT patients from 11/2016-05/2017; neither autologous HCT group was compensated. The collection rate was defined as the number of samples provided divided by the number of time points we attempted to obtain stool. Results: There were 35 allogeneic HCT patients in the intervention group, 19 allogeneic HCT patients in the historical control group, 142 autologous HCT patients in the contemporaneous control group (that did not receive a financial incentive), and 75 autologous HCT patients in the historical control group. Allogeneic HCT patients in the intervention group had significantly higher average overall collection rates when compared to the historical control group allogeneic HCT patients (80% vs 37%, p<0.0001). There were no significant differences in overall average collection rates between the autologous HCT patients in the contemporaneous control and historical control groups (36% vs 32%, p=0.2760). Conclusion : Our results demonstrate that a modest incentive can significantly increase collection rates. These results may help to inform the design of future studies involving stool collection. XXX Institutional Data Access / Ethics Committee (contact via XXX) for researchers who meet the criteria for access to confidential data.
The data underlying the results presented in the study are available from (include the name of the third party and contact information or URL). This text is appropriate if the data are owned by a third party and authors do not have permission to share the data. The gut microbiome can be studied with next-generation sequencing of microbial nucleic acids 69 that are extracted from human stool samples.   In order to control for potential differences in stool collection over two different time 112 periods, a contemporaneous control group was also included in the study design. The  to account for the correlation of the two rates for each patient. Other covariates such as age, 175 gender, race, disease, and conditioning type were adjusted for in order to avoid confounding. All 176 analyses were conducted using SAS version 9.4 (SAS Institute, Cary, NC) and R version 3.5.0. The allogeneic HCT patients in the intervention group displayed better compliance to 206 stool collection protocols than the allogeneic HCT patients in the historical control group (Table   207 3). For instance, the mean overall collection rate in the intervention group of allogeneic HCT 208 patients was much higher than the mean overall collection rate of the allogeneic HCT patients in 209 the historical control group (80% vs 37%, p<0.0001). In addition to an increased mean overall 210 collection rate, the allogeneic HCT patients in the intervention group also demonstrated 211 significantly increased mean outpatient collection rates (84% vs 23%, p<0.0001) and 212 significantly increased mean inpatient collection rates (71% vs 46%, p=0.0409). *Wilcoxon Rank Sum tests were used to test the rate differences.

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On the other hand, there were no differences in compliance to stool collection protocols 219 between the autologous patients in the contemporaneous control and historical control groups 220 (   addresses the possible confounders associated with potential discrepancies in stool collection 284 rates over time, strengthening our finding that the increase in collection rates can be attributed to 285 the financial incentive.

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Despite the effectiveness of the financial incentive, our study is not without limitations.

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For instance, although accounted for in the statistical analyses, there are considerable differences 288 in sample size between not only the comparison groups within each transplant type, but also 289 between the total number of allogeneic and autologous transplant patients included in the study.

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The difference in the number of allogeneic and autologous transplant study participants is 291 reflective of our patient population: about twice as many adult autologous stem cell transplants 292 are performed each year than adult allogeneic transplants at Duke. Another limitation of the 293 study is that the financial incentive was only made available to allogeneic transplant patients due 294 to funding restraints; this was accounted for by only performing comparisons within the same 295 transplant type. The non-randomization of the study is also a limiting factor because it does not 296 take into account confounders such as social determinants of health that may make someone 297 more or less inclined to participate in a research study involving financial incentives.

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Furthermore, although it was found that African American allogeneic transplant patients had 299 higher stool sample collection rates when compared to white allogeneic transplant patients, there 300 is a lack of racial and ethnic diversity in this study with the majority of study participants being 301 non-Hispanic whites.

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Effort on behalf of the patient is required most when providing a stool sample in the 303 outpatient setting since patients must do the collection process themselves, as opposed to the 304 inpatient setting where nursing staff aid with stool collection for admitted patients. Thus, the 305 formidable boost in collection rates in the outpatient setting in the intervention group underscore 306 the role of the financial incentive in this study. While the increase in inpatient collection rates in 307 the intervention group is still significant, the average inpatient collection rate associated with the 308 intervention group is mediated in the part by the role of nurses who work with patients to collect 309 samples in that setting. Also, inpatient collection time points may have been missed when 310 patients were only admitted for 24-48 hours for indications such as febrile neutropenia before 311 being discharged to continue antibiotics in the outpatient setting, thus leaving a very narrow 312 window for inpatient collection.

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While this study was performed in a specialized HCT patient population, this study 314 design utilizing financial incentives to increase stool collection rates may be able to be executed 315 in a myriad of patient populations. If these results are generalizable, other researchers attempting 316 to procure stool samples for microbiome studies may be able to increase their patient compliance 317 and improve their stool collection rates. Future directions for this study will be to observe the use 318 of financial incentives for stool collection in the HCT population longitudinally in order to 319 evaluate whether the effectiveness of the financial incentive would wear off over time.

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Furthermore, with more funding, autologous HCT patients can be included in the study. Another 321 next step is to investigate how social determinants of health affect stool collection rates in the 322 HCT population, identifying how factors such as socioeconomic status influence compliance and 323 willingness to participate in a study utilizing financial incentives.