Am J Clin Nutr. 2017 Dec;106(Suppl 6):1634S-1639S. doi: 10.3945/ajcn.117.155960. Epub 2017 Oct 25.
Serum ferritin as an indicator of iron status: what do we need to know?
Daru J1, Colman K2, Stanworth SJ3, De La Salle B4, Wood EM2, Pasricha SR5.
- 1 – Women’s Health Research Unit, Barts and the London School of Medicine, Queen Mary University of London, London, United Kingdom.
- 2 – Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
- 3 – NHS Blood and Transplant/Oxford University Hospitals NHS Trust, Oxford, United Kingdom.
- 4 – United Kingdom National External Quality Assessment Service, General Haematology, Watford, United Kingdom; and.
- 5 – Medical Research Council Human Immunology Unit, Medical Research Council Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom firstname.lastname@example.org.
Determination of iron status in pregnancy and in young children is essential for both clinical and public health practice. Clinical diagnosis of iron deficiency (ID) through sampling of bone marrow to identify the absence of body iron stores is impractical in most cases. Serum ferritin (SF) concentrations are the most commonly deployed indicator for determining ID, and low SF concentrations reflect a state of iron depletion. However, there is considerable variation in SF cutoffs recommended by different expert groups to diagnose ID. Moreover, the cutoffs used in different clinical laboratories are heterogeneous. There are few studies of diagnostic test accuracy to establish the sensitivity and specificity of SF compared with key gold standards (such as absent bone marrow iron stores, increased intestinal iron absorption, and hemoglobin response to SF) among noninflamed, outpatient populations. The limited data available suggest the commonly recommended SF cutoff of <15 μg/L is a specific but not sensitive cutoff, although evidence is limited. Data from women during pregnancy or from young children are especially uncommon. Most data are from studies conducted >30 y ago, do not reflect ethnic or geographic diversity, and were performed in an era for which laboratory methods no longer reflect present practice. Future studies to define the appropriate SF cutoffs are urgently needed and would also provide an opportunity to compare this indicator with other established and emerging iron indexes. In addition, future work would benefit from a focus on elucidating cutoffs and indexes relevant to iron adequacy.
KEYWORDS: cutoffs; diagnostic test; ferritin; hepcidin; iron deficiency; iron deficiency anemia; iron status