Impact of Workload and Shift Characteristics on Diagnostic Resource Utilization Among Emergency Medicine Residents.

Purpose: This study aimed to investigate the impact of shift characteristics, resident workload, and physician attributes on diagnostic expenditures in low-acuity patients (green triage category) emergency department (ED) patients. Methods: A retrospective cross-sectional analysis was conducted in a high-volume tertiary ED over one month, including 22,427 green-triage visits managed by 71 emergency medicine residents. Resident characteristics (age, gender, seniority, shift group, post-night shift status), patient demographics, and diagnostic expenditures (laboratory, imaging, electronic medication orders, total cost) were extracted from the hospital information system. Non-parametric tests were used for group comparisons given non-normal distribution patterns, and cost determinants were analyzed using a Gamma generalized linear model with a log-link function. Results: Diagnostic expenditures demonstrated significant variability across physician and patient characteristics. Female residents were associated with higher laboratory (1.27 vs 0.87 USD; p<0.001), imaging (1.35 vs 1.01 USD; p<0.001), and medication-order costs (p<0.001). Compared with junior residents, mid-level trainees generated the highest total expenditures, whereas senior residents exhibited a cost-attenuating effect (exp(β)=0.74). Unadjusted analyses indicated greater total spending during night shifts (2.8 USD vs 2.39-2.43 USD; p=0.011); however, after adjustment for resident- and patient-level covariates, night-shift status was associated with lower expenditures (exp(β)=0.76). Post-night-shift status independently correlated with reduced laboratory and medication-order costs. Resident workload showed a strong inverse association with expenditures, with increasing daily patient volume linked to lower total diagnostic costs (rho=-0.226; p<0.001). Among patient factors, advancing age increased total cost by approximately 6% per year (exp(β)=1.06). Repeat ED utilization emerged as the most powerful cost determinant, with each additional prior visit associated with more than a threefold increase in diagnostic spending (exp(β)>3; p<0.001). Female patients consistently incurred higher costs across all categories (p<0.001). Conclusion: Diagnostic spending in low-acuity ED encounters is shaped by both clinical and operational dynamics. Resident workload, seniority level, and gender independently influence cost patterns, while patient age and repeat admissions are strong drivers of increased expenditures. These findings highlight several potentially modifiable determinants-particularly workload distribution and trainee supervision-that may support more cost-conscious diagnostic practices in busy emergency departments.