Preoperative anaemia and iron deficiency in Wales: a national retrospective cohort study of postsurgical outcomes after major elective surgery

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Background Preoperative anaemia is common among patients undergoing major surgery and is associated with increased length of hospital stay, readmission, and mortality. Iron deficiency is the primary cause of preoperative anaemia. This study aimed to describe the prevalence of anaemia and iron deficiency across surgical specialties in Wales and their impact on postoperative outcomes during the introduction of a nationwide patient blood management model. Methods We conducted a retrospective cohort study of adult patients (aged ≥18 yr) undergoing major elective surgery (gastrointestinal, cardiac, urologic, gynaecologic, orthopaedic) between January 2018 and May 2025. As part of the NHS Wales Preoperative Anaemia Pathway, anaemia was defined as a haemoglobin concentration of <130 g L −1 . Iron deficiency was defined as a serum ferritin concentration of <30 μg L −1 or transferrin saturation of <20%, with inflammation defined as a C-reactive protein concentration of >10 mg L −1 . Data collected included patient characteristics, Charlson Comorbidity Index, laboratory results, length of hospital stay, 30-day readmission, and mortality (30-day, 90-day, 1-yr, and 5-yr). Results Among 46 614 patients, 31% were anaemic, with 52% of anaemic patients having iron deficiency. Preoperative anaemia was independently associated with prolonged length of hospital stay (adjusted rate ratio 1.17, 95% confidence interval [CI] 1.16–1.18), increased 30-day readmission (adjusted odds ratio 1.18, 95% CI 1.09–1.27), and higher mortality at all time points (adjusted odds ratio 1.69, 95% CI 1.54–1.85). Iron deficiency and anaemia with inflammation were associated with particularly poor outcomes. Conclusions Preoperative anaemia and iron deficiency are prevalent in the surgical population and linked to worse short-term and long-term outcomes. These findings have implications for routine screening before surgery.