The value of the Thomas-plot in the diagnostic work up of anemic patients referred by general practitioners

P>In patients with inflammatory conditions, diagnosing classic iron deficiency or anemia of chronic disease is challenging. In this study, we assessed the diagnostic value of the so-called Thomas'-plot [soluble transferrin receptor (sTfR)/log ferritin (sTfr/log Ferr) and the reticulocyte hemoglobin equivalent (Ret-HE)] in the anemia work up of patients referred by general practitioners. During July 2008-March 2009, 337 consecutive patients were included because of lowered Hb values. The laboratory results of the first 133 consecutive patients were used to determine the cut-off values for the diagnostic plot. The laboratory results of these patients were assessed and interpreted independently by two investigators, blinded from sTfR/log Ferr and Ret-HE values. The following 204 patients were used to test the plot in practice. In 32% of the first 133 patients, no indication of the cause of anemia could be found. However, when using the diagnostic plot in the following 204 patients, this fraction decreased to 14%. The 'Thomas'-plot is of diagnostic value for distinguishing functional iron deficiency from classic iron deficiency in a patient population referred by general practitioners.