Biomarkers in preoperative iron deficiency with and without anemia: a scoping review

Abstract Background Preoperative anemia is associated with poor postoperative outcomes. The detection and treatment of iron deficiency with or without anemia ID(A) is an essential part of Patient Blood Management (PBM) programs. Hemoglobin, transferrin, and transferrin saturation (TSAT) are commonly used biomarkers for diagnosis, prediction or prognosis of ID(A). Although these biomarkers are routinely used to diagnose ID(A) a variety of guideline-recommended cut-off values exists. This scoping review (ScR) maps the existing evidence regarding type and cut-off values for diagnostic, predictive, and prognostic biomarkers in surgical patients with ID(A). Methods MEDLINE (via Ovid) and the Cochrane Central Register of Controlled Trials (CENTRAL) (via Cochrane Library) were systematically searched for published studies up to April 25, 2023. Study selection and data extraction were performed independently by two reviewers. In accordance with the mapping purpose of this scoping review, no formal critical appraisal or risk-of-bias assessment was undertaken. The ScR focused on surgical patients ≥ 18 years in which blood-based or non-invasive biomarkers were used (1) to diagnose ID(A), (2) to predict efficacy or safety of iron supplementation with or without erythropoietin (EPO), and (3) to assess the prognostic value of biomarkers for adverse intra- and postoperative outcomes (until hospital discharge) in patients with laboratory-confirmed ID(A). Results Out of 7,381 records, seven studies (two diagnostic and five prognostic) were included. Across the seven included studies, diagnostic accuracy for iron deficiency varied substantially between biomarkers, with conventional iron parameters and novel markers demonstrating heterogeneous sensitivity and specificity. The prognostic studies reported associations between iron-related biomarkers or iron-status categories and hemoglobin response, postoperative hemoglobin concentrations, transfusion requirements, complications, or survival. Owing to substantial heterogeneity and the small evidence base, the direction and magnitude of these associations remain uncertain.. Patients with ID(A) generally exhibited more pronounced Hb increases following iron therapy compared with those with functional iron deficiency, anemia of inflammation, or replete iron stores. Conclusion This ScR provides an overview of the current evidence on biomarkers in preoperative ID. However, significant research gaps remain, particularly regarding: (1) the assessment of biomarkers for diagnosing ID in preoperative patients; (2) predictive biomarkers for ID(A); (3) studies focusing exclusively on preoperative patients with laboratory-confirmed ID.