The aetiology and prevalence of preoperative anaemia in patients undergoing major surgery (ALICE): an international, prospective, observational cohort study

Abstract

Background Preoperative anaemia is a major risk factor for perioperative morbidity. Because iron deficiency is widely assumed to be the main cause of anaemia in surgical patients, treatment efforts have focused mostly on iron supplementation. However, the aetiology of anaemia is multifactorial. To further understand the underlying causes and consider a comprehensive approach to anaemia management, we studied the prevalence and aetiology of preoperative anaemia in patients undergoing major surgery. Methods This prospective, multicentre, observational cohort study was done in 79 hospitals in 20 countries on five continents; patients were aged at least 18 years, undergoing major surgery, and had a postoperative in-hospital stay of at least 24 h. Patients donating autologous blood before surgery were excluded. Data were extracted from the electronic hospital information system and from self-reported information during preoperative examination. The primary outcomes were the prevalence of anaemia, defined as haemoglobin less than 120 g/L for women and less than 130 g/L for men, analysed in all participants, and the aetiology of anaemia, analysed only in patients with anaemia for whom aetiology could be confirmed. The study was registered with ClinicalTrials.gov (NCT03978260) and is complete. Findings Between Aug 26, 2019, and Dec 26, 2021, 2830 patients undergoing major surgery were recruited and 2702 patients were included in the analysis (1417 [52·4%] were male, 1279 [47·3%] were female, and six [0·2%] had gender dysphoria). Overall, 856 (31·7%, 95% CI 31·2–32·2) patients had preoperative anaemia. Among 782 patients with preoperative anaemia, for whom the presence of at least one aetiology could be confirmed, 432 (55·2%, 48·9–61·6) had iron deficiency, 60 (7·7%, 6·6–8·7) had vitamin B12 deficiency, 113 (14·5%, 12·2–16·7) had folate deficiency, 68 (8·7%, 8·1–9·3) had chronic kidney disease, and 48 (6·1%, 4·5–7·8) had anaemia resulting from another cause; patients could be assigned to multiple aetiologies. Across male and female sex, all age groups, and all countries, iron deficiency was the aetiology with the highest prevalence. Interpretation The prevalence of preoperative anaemia in patients in this study who were undergoing major surgery is high. Iron deficiency is the primary cause of this anaemia; however, the substantial prevalence of vitamin B12 and folate deficiencies demands immediate attention and action.