Background: Anemia is common among colorectal surgery patients and is associated with worse clinical outcomes. Single centre studies suggest a strong association with increased healthcare costs. Understanding the population-level, health-system costs attributable to anemia will inform efforts to address anemia at a health system level. Therefore, our objective was to investigate the association of preoperative anemia with health system costs among adult elective colorectal surgery patients.

Methods: This was a population-based cohort study in Ontario, Canada. Following protocol registration, linked health administrative data from ICES was used to identify Ontario residents aged 18 years and over who underwent an elective colorectal resection between April 1st, 2012 and March 31st, 2022. Primary exposure was preoperative anemia as defined by the World Health Organization (Hemoglobin <130g/L in males and <120g/L in females). The primary outcome was costs in Canadian 2022 dollars, from the perspective of the publicly funded health care system accrued within 30 days of surgery. Secondary outcomes included health system costs at 90- and 365-days after surgery, red blood cell transfusion, major adverse events (MAE), length of hospital stay (LOS), days alive at home (DAH), and readmissions. Generalized linear models were used to analyze outcome differences between exposure levels, with adjustment for various pre-specified confounders.

Results: Among 54,286 patients, 21,264 (39.2%) had preoperative anemia. There was an absolute adjusted cost increase of $2,671 per person at 30-days following surgery, that was attributable to the presence of preoperative anemia (Ratio of Means [RoM] 1.05, 95% Confidence Interval [CI] 1.04-1.06). RoM at 90- and 365-days following index surgery was 1.10 (95% CI 1.08-1.11) and 1.16 (95% CI 1.15-1.18) with mean absolute adjusted cost differences of $4,748 and $10,435, respectively. Compared to the control group, 30-day risk of transfusion (Odds Ratio [OR] 4.34, 95% CI 4.04-4.66), MAE (OR 1.14, 95%CI 1.03-1.27), LOS (RoM 1.08, 95% CI 1.07-1.10), and readmissions (adjusted OR 1.16, 95% CI 1.08-1.24) were also higher in the anemia group with reduced DAH (RoM 0.95, 95% CI 0.95-0.96).

Conclusions: We estimate that $2,671 CAD (approximately $2,053 USD) in 30-day health system costs are attributable to pre-operative anemia following colorectal surgery in Ontario, Canada. These data can inform health system planning and economic considerations in developing and implementing effective anemia management strategies.

Daniel McIsaac

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