Original article A ferritin level N 50 μg/L is frequently consistent with iron deficiency ☆ Anastasios Koulaouzidis a, ⁎ , Russell Cottier a , Shivaram Bhat a , Elmuhtady Said b , Barry D. Linaker a , Athar A. Saeed b a Warrington General Hospital, Lovely Lane, WA5 1QG, Warrington, Cheshire, UK b Queen Elizabeth Hospital, Sherriff Hill Road, NE9 6SX, Gateshead, Tyne and Wear, UK Received 30 January 2007; received in revised form 8 September 2007; accepted 26 September 2007 Available online 5 August 2008 Abstract Background: The British Society of Gastroenterology (BSG) suggests that a serum ferritin level ≤ 50 μg/L is still consistent with iron deficiency in the presence of coexistent pathology (inflammation, infection or malignancy), by implication excluding iron deficiency above this level. We aim to examine the validity of this cut-off level in three different groups of patients. Methods: We used the soluble transferrin receptor/Log 10 ferritin ratio (sTfR-F Index or Index) as a determinant of body iron stores. If the Index was equal or more than 2, the patients were considered iron deficient. Patients were considered iron replete if Index was ≤ 1. The data was prospectively collected over a period of 3 years. All patients had normocytic anaemia. Results: We collected data for 198 patients. Ninety-three had a sTfR-F Index ≥ 2 and 17 had Index ≤ 1. If a ferritin level ≤ 50 μg/L was used as the cut-off value for iron deficiency, the negative predictive value (NPV) of ferritin test was 22% and the positive predictive value (PPV) 100%; if the level is raised to 100 μg/L the NPV of ferritin test rose to 34.8% and the PPV was 97%. Conclusion: Patients with normocytic anaemia who have ferritin levels above 50 μg/L should not automatically be considered to have adequate iron stores. We suggest that the integration of sTfR-F Index in the diagnostic workup of these patients can improve patient care. © 2008 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. Keywords: Iron deficiency; Ferritin; Soluble transferrin receptor; sTfR-F Index; Bone marrow; British Society of Gastroenterology 1. Introduction Serum ferritin is used as a marker of iron storage and a level of b 15 μg/L is generally taken as an indicator of absent iron stores. However, ferritin levels tend to rise with age [1], acute and chronic sepsis, inflammation and malignancies, so that a ferritin level of 30 μg/L provides better positive predictive values for iron deficiency anaemia (92–98%) when studied in several populations [2]. Furthermore, in a landmark study of 259 elderly anaemic patients Guyatt et al. found that 40% of subjects with ferritin levels between 18 and 100 μg/L had iron deficiency anaemia (IDA) [3,4]. Bone marrow aspiration is still widely regarded as the ‘gold standard’ test to detect iron status but it is invasive, difficult to perform and is user dependent [5]. The first description of the presence of transferrin receptors on the surface of the reticulocytes was made in 1963 [6] and they were further characterised as a cell surface glycoprotein in 1981 [7]. Soluble transferrin receptors (sTfR) were described as an index of erythropoiesis in 1987 [8]. The receptor is a dimer of two 95 kD polypeptide molecules linked by disulfide bonds. Virtually all body cells present transferrin receptors on their surface with the largest number found on the erythron. The ratio sTfR/Log 10 ferritin (sTfR-F Index) has now been established as a useful alternative in assessing the iron status of patients, especially those with concurrent illness [9,2]. We conducted an analysis aiming to check the validity of ferritin level of 50 μg/L European Journal of Internal Medicine 20 (2009) 168 – 170 www.elsevier.com/locate/ejim ☆ Support acknowledgement: The authors thank Siemens Diagnostics for the kind sponsorship with the sTfR assay at Warrington General Hospital. ⁎ Corresponding author. Present address: Centre for Digestive and Liver Disorders, Royal Infirmary of Edinburgh, 51 Little France Crescent, EH164SA, Edinburgh, Scotland, UK. Tel.: +44 131 5361000. E-mail address: akoulaouzidis@hotmail.com (A. Koulaouzidis). 0953-6205/$ - see front matter © 2008 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.ejim.2007.09.024