Utility of Access Soluble Transferrin Receptor (sTfR) and sTfR/log Ferritin Index in Diagnosing Iron Deficiency Anemia

The Access(®) soluble transferrin receptor (sTfR) is considered the world's first automated chemiluminescence immunoassay. In this study, the diagnostic utility of this and other tests for serum iron were evaluated by studying their interrelationships with inflammation. A total of 367 patients with anemia (iron deficiency anemia [IDA], 157; anemia of chronic disease [ACD], 210) and 80 normal controls were subjected to a battery of diagnostic tests, including complete blood cell count, serum iron, total iron-binding capacity (TIBC), C-reactive protein (CRP), ferritin, sTfR, and hepcidin. The accuracy of test parameters was determined by the area under the receiver operating characteristic curve (AUC). Patients falling within the ferritin grey zone (10-100 ng/ml) were evaluated separately, given that such individuals are typically difficult to detect and manage in actual clinical practice. CRP was used to assess the correlation between the aforementioned markers of iron and inflammation. The single most accurate diagnostic test used to differentiate IDA from ACD was serum ferritin (AUC 0.989). However, sTfR assay outperformed other tests in the ferritin grey zone (AUC 0.931), and the sTfR/log ferritin index was the most reliable parameter in both scenarios (AUC 0.994 and 0.962, respectively). Ferritin, TIBC, and hepcidin showed the highest correlation with CRP, whereas sTfR displayed the lowest. The Access sTfR and sTfR/log ferritin index enabled highly accurate diagnosis of IDA in the ferritin grey zone. This is an easy-to-use automated chemiluminescence immunoassay, amenable to routine use in hospitals.