Associations of Preoperative Anaemia with Healthcare Resource Use and Outcomes after Colorectal Surgery: a Population-Based Cohort Study

Background: Preoperative anaemia is common in patient undergoing colorectal surgery. Understanding the population-level costs of preoperative anaemia will inform development and evaluation of anaemia management at health system levels. Methods: This was a population-based cohort study using linked, routinely collected data, including residents from Ontario, Canada, aged >= 18 yr who underwent an elective colorectal resection between 2012 and 2022. Primary exposure was preoperative anaemia (haemoglobin < 130 g L (- 1) in males; < 120 g L (- 1) in females). Primary outcome was 30-day costs in 2022 Canadian dollars (CAD), from the perspective of a publicly funded healthcare system. Secondary outcomes included red blood cell transfusion, major adverse events (MAEs), length of stay (LOS), days alive at home (DAH), and readmissions. Results: We included 54,286 patients, with mean 65.3 (range 18 - 102) years of age and 49.0% females, among which 21264 (39.2%) had preoperative anaemia. There was an absolute adjusted cost increase of $2671 per person at 30 days after surgery attributable to preoperative anaemia (ratio of means [RoM] 1.05, 95% confidence interval [CI] 1.04 - 1.06). Compared with the control group, 30-day risks of transfusion (odds ratio [OR] 4.34, 95% CI 4.04 - 4.66), MAEs (OR 1.14, 95% CI 1.03 - 1.27), LOS (RoM 1.08, 95% CI 1.07 - 1.10), and readmissions (OR 1.16, 95% CI 1.08 - 1.24) were higher in the anaemia group, with reduced DAH (RoM 0.95, 95% CI 0.95 - 0.96). Conclusions: Approximately $2671 CAD per person in 30-day health system costs are attributable to preoperative anaemia after colorectal surgery in Ontario, Canada.