Screening failures in healthy volunteers participating in early-phase clinical trials

Introduction . Screening of healthy volunteers is an essential stage of Phase I clinical trials and bioequivalence studies, ensuring participant safety and the quality of the study population. A high rate of screening failures leads to prolonged recruitment periods, additional costs, and reduced efficiency of clinical trial conduct. However, data on the structure of screening failure causes and associated risk factors remain limited. Aim . To assess the frequency of screening failures, identify the main causes of screening failure among healthy volunteers, and evaluate the influence of demographic factors on screening outcomes. Materials and methods . A retrospective analysis of screening data from 1,000 healthy volunteers evaluated for participation in Phase I clinical trials and bioequivalence studies was performed. All participants underwent clinical examination, electrocardiography, laboratory testing of blood and urine, screening for infectious disease markers, and testing for alcohol and illicit drugs. Statistical analysis included descriptive statistics, the χ² test, Student’s t-test, and ROC analysis. Results. Screening failures were identified in 175 volunteers (17.5%). The main causes of screening failure were abnormalities in biochemical blood parameters (31%), followed by deviations in complete blood count, inability to comply with study protocol requirements, detection of infectious markers, electrocardiographic abnormalities, and blood pressure deviations. The frequency of screening failures was not associated with sex (p = 0.164). Volunteers older than 40 years had a higher risk of screening failure, primarily due to age-related metabolic abnormalities. Conclusion. Laboratory abnormalities, particularly deviations in biochemical blood parameters, represent the leading cause of screening failures among healthy volunteers. Age is a significant risk factor for screening failure, whereas the effect of sex on the overall screening failure rate was not statistically confirmed. The findings may be used to improve volunteer pre-screening algorithms, enhance recruitment efficiency, and optimize the conduct of early-phase clinical trials and bioequivalence studies.