Prevalence of Iron Deficiency Anemia in Community-Dwelling Older Persons as Measured by the Transferrin Receptor-Ferritin Index

community-dwelling older adults using the sTfR-F index. We conducted the anemia survey in three urban districts (Guro, Yangcheon and Gwanak) located in the southwestern part of Seoul in 2002. In this survey, a total of 1,254 subjects over the age of 60 years were selected from a cross-sectional study, the results of which have been published previously [2] . In brief, all the subjects lived in their own homes and were fully ambulatory with unlimited activities of daily living. Informed consent was obtained from all subjects, and then a complete medical history was taken and laboratory testing including a complete blood cell count with a reticulocyte count and iron profi les was performed. Anemia was defi ned according to the World Health Organization criteria, i.e. a hemoglobin level of ! 13 g/dl in men and ! 12 g/dl in women. In case of anemia, we performed the sTfR assay using a commercial kit based on a polyclonal antibody in a sandwich enzyme immunoassay (R&D Systems, Minneapolis, Minn., USA). According to the manufacturer, the central 95th percentile of the reference distribution of the sTfR concentration is 8.7–28.1 nmol/l. We then calculated the sTfR-F index (ratio of sTfR and log ferritin level). All the sTfR assays were performed in duplicate. IDA was considered present if the subject had anemia and the sTfR-F index was 1 1.5. Anemia is the most common hematologic problem encountered in older adults, and its prevalence increases with age [1, 2] . The common causes of anemia among older persons are anemia of chronic disease, iron defi ciency caused by gastrointestinal bleeding, cobalamin defi ciency, folate defi ciency and the myelodysplasia. Among these causes, the diagnosis of iron defi ciency anemia (IDA) is important because proper iron therapy can improve the symptoms, and treatment may help indicate an occult gastrointestinal pathology such as malignancy [3, 4] . There are few reports regarding the prevalence of IDA in older persons, and epidemiologic studies on East Asian populations are scarce. Moreover, the results of such studies have been variable according to the diagnostic criteria used. Previously published reports have used serum ferritin levels to diagnose IDA, but the cutoff levels were different in the various studies. The interpretation of the serum ferritin level in older adults is sometimes complicated because its level increases with age and with concomitant chronic illnesses [5, 6] . Therefore, we measured the soluble transferrin receptor (sTfR), which is not infl uenced by ageing or chronic diseases [7, 8] , and we calculated the ratio of sTfR to the log ferritin level (sTfR-F index) to make the test more specifi c. An index value of