Beyond Iron Deficiency: Unveiling the Prevalence of Folate and Vitamin B12 Deficiencies in Major Surgical Patients

Mischa J Kotlyar; Patrick Meybohm; Lotta Hof; Maike Koch; Lea Valeska Blum; Jan Andreas Kloka; Denana Mehic; Vanessa Neef; Kai Zacharowski; Suma Choorapoikayil

doi:10.1159/000548891

Beyond Iron Deficiency: Unveiling the Prevalence of Folate and Vitamin B12 Deficiencies in Major Surgical Patients

Transfus Med Hemother. 2025 Nov 7. doi: 10.1159/000548891. Online ahead of print.

Affiliations

¹ Department of Anaesthesiology, Intensive Care, Emergency and Pain Medicine, University Hospital Würzburg, Würzburg, Germany.
² Department of Anaesthesiology, Intensive Care and Pain Therapy, Goethe University Frankfurt, University Hospital Frankfurt, Frankfurt, Germany.

Abstract

Introduction: Preoperative anaemia is associated with increased morbidity and mortality in surgical patients. While iron deficiency is a well-recognized cause, the contribution of other nutritional deficiencies, such as folate and vitamin B12, remains underexplored. Therefore, this study aimed to assess the prevalence and role of folate and vitamin B12 deficiencies in preoperative anaemia among patients undergoing major surgery.

Methods: This retrospective observational study included 410 patients aged ≥18 years who underwent major surgery and were evaluated at a preoperative anaemia clinic in a large tertiary hospital between June 2016 and June 2023. Key outcome measures included the prevalence of iron, folate, and vitamin B12 deficiencies and their associations with preoperative anaemia.

Results: Anaemia was observed in 41.5% (95% confidence interval [CI]: 36.8-46.3), iron deficiency in 51.5% (95% CI: 46.6-56.3), folate deficiency in 18.0% (95% CI: 14.6-22.1), and vitamin B12 deficiency in 3.2% (95% CI: 1.9-5.4). Anaemic patients exhibited higher rates of iron (61.8%, 95% CI: 54.3-68.7 vs. 44.2%, 95% CI: 38.0-50.5) and folate deficiencies (27.1%, 95% CI: 20.9-34.2 vs. 11.7%, 95% CI: 8.2-16.3, p < 0.001) compared to non-anaemic patients. Combined deficiencies, primarily iron and folate, were more frequent in anaemic patients (17.7%, 95% CI: 12.7-24.1 vs. 7.5%, 95% CI: 4.8-11.5, p = 0.003). Substantial heterogeneity in deficiency patterns was observed across surgical subgroups, with overall prevalences ranging from 20% to 59% for iron, and from 11% to 31% for folate. Iron (odds ratio [OR] 3.27, 95% CI: 2.03-5.27, p < 0.001) and folate (OR 2.6, 95% CI: 1.45-4.59, p = 0.001) deficiencies were independently associated with anaemia and together accounted for approximately one-third of preoperative anaemia cases.

Conclusion: Iron deficiency remains the predominant contributor to preoperative anaemia, with folate deficiency playing a significant yet underrecognized role. The high occurrence of combined deficiencies and substantial heterogeneity across surgical populations support the need for population-specific diagnostic and supplementation strategies.

Keywords: Folate deficiency; Iron deficiency; Malnutrition; Preoperative anaemia; Vitamin B12 deficiency.