Iron deficiency in athletes – new guidelines for diagnosis and treatment

Abstract

Background: Iron deficiency (ID), worldwide a common affection is associated with reduced performance, fatigue and increased risk for infections. Athletes are a risk-population due to a higher prevalence of restrictive diets or exercise-induced inflammation. Particularly in athletes, the diagnosis of ID based on unspecific symptomes or routine laboratory diagnostics with ferritin is not always reliable. The goal of this study was therefore to discover if a new diagnostic approach adding zinc protoporphyrin (ZnPP) or soluble transferrin receptor (sTfR) in the routine assessment of ID in athletes is helpful or even necessary. Methods: 603 competitive Swiss athletes were assessed during their annual pre-participation examination. A standardized questionnaire was used to gather information about potential predictors like age, gender, BMI, vegetarian diet, ID symptoms and iron substitution. Based on ZnPP or sTfR we divided the athletes in 3 ID-stages: 1. Storage ID, 2. Non-anemic ID (NAID), 3. ID anemia (IDA). Storage ID (Stage I) or a IDA (Stage III) was diagnosed based on gender- and age-adjusted ferritin and hemoglobin values. ZnPP-values > 75 mmol/mol heme and sTfR-values > 1.55 mg/ml were chosen as indicators for an iron-deficient erythropoiesis (NAID, Stage II). Results: 19% of the athletes presented low ferritin-values, 16% or 15% showed a NAID based on ZnPP or sTfR. 5–6% presented a NAID with normal ferritin-values (“false negative”) and 14% showed low ferritin-values, but normal ZnPP and sTfR (“false positive”). 3% of the athletes had an IDA. Female sex and young age (<18 years), but not the presence of ID symptoms or iron substitution were significant predictors for a clinically relevant ID (Stage II–III). Implication: Adding ZnPP or sTfR in the diagnosis of the clinically important NAID approach of ID in athletes lead to a more precise diagnosis of an ID of clinical importance. This is of importance especially in athletes who often present with falsely normal ferritin values due to exercise-induced inflammation. Athletes with NAID or IDA (high ZnPP/sTfR values and/or low hemoglobin) should obtain an oral iron substitution, independently of ferritin values. This approach should, however, be verified in a longitudinal study, ideally by a randomized and placebo-controlled trial.