Preoperative laboratory investigations: rates and variability prior to low-risk surgical procedures

Background — Increasing attention has been focused on low-value healthcare services. Through Choosing Wisely campaigns, routine laboratory testing before low-risk surgery has been discouraged in the absence of clinical indications. The authors investigated rates, determinants, and institutional variation in laboratory testing before low-risk procedures.

Methods — Patients who underwent ophthalmologic surgeries or predefined low-risk surgeries in Ontario, Canada, between April 1, 2008, and March 31, 2013, were identified from population-based administrative databases. Preoperative blood work was defined as a complete blood count, prothrombin time, partial thromboplastin, or basic metabolic panel within 60 days before an index procedure. Adjusted associations between patient and institutional factors and preoperative testing were assessed with hierarchical multivariable logistic regression. Institutional variation was characterized using the median odds ratio.

Results — The cohort included 906,902 patients who underwent 1,330,466 procedures (57.1% ophthalmologic and 42.9% low-risk surgery) at 119 institutions. Preoperative blood work preceded 400,058 (30.1%) procedures. The unadjusted institutional rate of preoperative blood work varied widely (0.0 to 98.1%). In regression modeling, significant predictors of preoperative testing included atrial fibrillation (adjusted odds ratio [AOR], 2.58; 95% CI, 2.51 to 2.66), preoperative medical consultation (AOR, 1.68; 95% CI, 1.65 to 1.71), previous mitral valve replacement (AOR, 2.33; 95% CI, 2.10 to 2.58), and liver disease (AOR, 1.69; 95% CI, 1.55 to 1.84). The median odds ratio for interinstitutional variation was 2.43.

Conclusions — Results of this study suggest that testing is associated with a range of clinical covariates. However, an association was similarly identified with preoperative consultation, and significant variation between institutions exists across the jurisdiction.