B-138 Skewed Demographics of Patient Population Contributes to Selection Biases in Clinical Study Population
Authors: Vettleson-Trutza S , Yang Y , Snyder M , Jazdzewski D 
Published: September 2023

Background

The racial, ethnic and sex compositions of a study population may impact the clinical performance of a biomarker. In a prospective clinical study to evaluate biomarkers for asthmatic and allergic conditions in a large medical center in the upper Midwest, a largely White-alone patient population was encountered. Using several outreach strategies, potential eligible patients were contacted to enroll in a biomarker clinical study and to provide blood specimens. The patient demographics between the eligible candidates and the enrolled participants were compared. The analysis was carried out to understand the likelihood of enrollment in different race, ethnicity, and sex groups; and to identify factors that contribute to selection biases in enrolled cohorts.

Methods

Patients with eligible asthma and allergic conditions were selected based on relevant diagnostic codes in their electronic medical records, verified by clinical research coordinator. In accordance with Institutional Review Board approval, eligible patients were contacted via their electronic healthcare portal or with a phone call. The study information was also posted in an internal classified ad as an additional outreach strategy. Interested participants were then contacted a second time to complete consent. Upon consent, participants were considered as “enrolled”. Demographics information including sex, race, ethnicity, and age were de-identified for comparison analysis.

Results

Among all eligible patients, a disproportionally low representation of Blacks, Asians, and Hispanics (“non-White” groups) was observed, relative to regional demographics (22.2% non-White groups, 2021 census) and higher asthma and allergy prevalence in the non-White groups. In eligible adult patients (&gt;18 years old) with asthma, only 13.4% were from non-White racial and ethnic groups. In eligible pediatric asthma patients, a larger proportion at 24.1% were from American Indian, Asian, Black, or Hispanic groups. In patients with allergic conditions, 10.3% of the adult patients were from non-White only groups, compared to 21.9% in pediatric patients. Among all eligible patients, White-alone patients were more likely to enroll in the study compared to their counterparts from non-White groups, further skewing the racial and ethnic distribution in the enrolled cohorts. As a result, less than 10% of enrolled adult patients were from non-White background in both allergy and asthma cohorts. Among the enrolled pediatric asthma and allergy patients, 16.9% and 10.3% respectively were from non-White groups. We also identified sex and age dependent enrollment behavior across different study cohorts. In adult groups, there were more female eligible patients (allergy: 66.7% female; asthma: 66.7% female) than male patients. Female adult patients were significantly more likely to participate, thus constituting 79.6% and 75.8% of the enrolled allergy and asthma cohorts. In the pediatric groups, male patients represented a larger share of eligible patients (allergy: 58.6%; asthma 64.7%). Female pediatric patients were still more likely to participate in the study. Hence, male and female enrolled patients were closer to equal distribution (allergy: 50.0% male; asthma 59.7% male).

Conclusion

The non-even distribution of demographics in eligible patients contributed to biased distribution in enrolled patients. Existing outreach approaches were not effective in reversing enrollment rates in underrepresented racial and ethnic groups.