Clin. Lab. Haem. 1999, 21, 161–167 Serum soluble transferrin receptor and the prediction of marrow aspirate iron results in a heterogeneous group of patients R.T. MEANS Jr Hematology/Oncology Division, Medical University of South Carolina, Charleston, SC, USA and J. ALLEN* the University of Cincinnati, Cincinnati, OH, USA, D.A. SEARS† *R & D Systems, Inc., Minneapolis, MN, USA, S.J. SCHUSTER‡ †Department of Medicine, Baylor College of Medicine, Houston, TX, USA and ‡Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, PA, USA Summary Serum soluble transferrin receptor (sTfR) concentration has been evaluated in the diagnosis of iron deficiency in otherwise healthy individuals and in patients with rheumatoid arthritis, but has not been studied in a general population of patients with complicated clinical presentations. In this study, 145 anaemic patients with a variety of medical conditions undergoing diagnostic bone marrow aspiration for any reason were tested by a complete blood count, a panel of biochemical tests to evaluate iron status, bone-marrow aspirate iron stain, and serum sTfR concentration. Sixteen per cent lacked stainable iron in the marrow aspirate. All biochemical parameters differed significantly between patients with or without stainable marrow iron. The sTfR assay was significantly more sensitive but less specific than other iron status assays in identifying the absence of stainable iron. Logistic regression analysis demonstrated that only sTfR and ferritin contributed independently to the prediction of marrow iron status. Serum ferritin alone was highly specific but insensitive. A decision algorithm combining serum ferritin and sTfR was as sensitive as TfR and as specific as serum ferritin. The measurement of serum sTfR, especially in conjunction with serum ferritin, is a valuable addition to the existing methods for predicting the results of marrow aspirate iron stains. Keywords Anaemia, bone marrow aspirate, ferritin, iron deficiency, transferrin receptor Introduction Iron deficiency in adults is usually the result of a loss of iron through blood loss in excess of dietary iron absorption. Since iron deficiency is commonly a presenting feature of gastrointestinal disease, including malignancies, its prompt and reliable diagnosis is essential, even if the degree of anaemia is not severe. The traditional biochemical assessment of iron status includes measurement of serum ferritin, a reflection of total body iron stores; serum iron, a measure of immediately available iron; serum transferrin or total iron binding capacity (TIBC), a measure of the iron transport system; and transferrin saturation (the ratio of serum iron to TIBC Accepted for publication 15 January 1999 Correspondence: Dr R.T. Means Jr, Medical University of South Carolina, Hematology/Oncology, Suite 903, Box 250623, 96 Jonathan Lucas Street, Charleston SC29425, USA. This study was sponsored by R & D Systems, Inc., Minneapolis, MN, USA. © 1999 Blackwell Science Limited expressed as a percentage) (Worwood 1994). Diagnosis of iron deficiency using these laboratory tests is straight- forward for individuals who are otherwise in good health. Iron deficiency can be diagnosed when the ferritin con- centration is below the normal range or if other values are, in general, consistent with iron deficiency (i.e. decreased serum iron with elevated TIBC, producing a marked decrease in transferrin saturation). In clinical practice, the most common causes of anaemia are iron deficiency and the anaemia of chronic disease, which is a syndrome traditionally associated with chronic inflammatory, malignant or infectious diseases, but also with a variety of other conditions associated with activation of the cytokines involved in the immune or inflammatory response (Cash & Sears 1989; Lipschitz 1990; Means & Krantz 1992). Iron deficiency anaemia and the anaemia of chronic disease are both associated with a decreased serum iron and in many cases with a decreased erythrocyte mean corpuscular volume. These two syndromes may be dif- 161