Association Between Health System Factors and Utilization of Routine Laboratory Tests in Clinical Teaching Units: a Cohort Analysis

Abstract

Background: Few studies have looked at health system factors associated with laboratory test use.

Objective: To determine the association between health system factors and routine laboratory test use in medical inpatients.

Design: We conducted a retrospective cohort study on adult patients admitted to clinical teaching units over a 3-year period (January 2015 to December 2017) at three tertiary care hospitals in Calgary, Alberta.

Participants: Patients were assigned to a Case Mix Group+ (CMG+) category based on their clinical characteristics, and patients in the top 10 CMG+ groups were included in the cohort.

Exposures: The examined health system factors were (1) number of primary attending physicians seen by a patient, (2) number of attending medical teams seen by a patient, (3) structure of the medical team, and (4) day of the week.

Main measures: The primary outcome was the total number of routine laboratory tests ordered on a patient during their admission. Statistical models were adjusted for age, sex, length of stay, Charlson comorbidity index, and CMG+ group.

Results: The final cohort consisting of 36,667 patient-days in hospital (mean (SD) age 62.5 (18.4) years) represented 5071 unique hospitalizations and 4324 unique patients. Routine laboratory test use was increased when patients saw multiple attending physicians; with an adjusted incidence rate ratio (IRR) of 1.46 (95% CI, 1.37-1.55) for two attending physicians, and 2.50 (95% CI, 2.23-2.79) for three or more attending physicians compared to a single attending physician. The number of routine laboratory tests was slightly lower on weekends (IRR 0.98, 95% CI, 0.96-0.99) and on teams without a senior resident as part of their team structure (IRR 0.89, 95% CI 0.830.96).

Conclusions: The associations observed in this study suggest that breaks in continuity of care, including increased frequency in patient transfer of care, may impact the utilization of routine laboratory tests.

Keywords: clinical teaching units; continuity of care; inpatients; low value care; routine laboratory testing.