The soluble transferrin receptor (TfR)-F-Index is not applicable as a test for iron status in patients with chronic lymphocytic leukemia

BACKGROUND: The soluble transferrin receptor (sTfR) is established as a test for iron deficiency (ID). In chronic lymphocytic leukemia (CLL), sTfR is not reliable for screening for ID as the latter is strongly dependent on tumor burden. METHODS: We investigated whether the influence of the tumor load can be excluded or minimized using the sTfR/log ferritin ratio (TfR-F-Index) and the C-reactive protein (CRP)-adjusted TfR-F-Index in 87 patients with CLL. sTfR was measured nephelometrically (normal: 0.81-1.75 mg/L). A cut-off value of 1.5 for the TfR-F-Index and 0.8 for the CRP-adjusted TfR-F-Index, in patients with a CRP >5 mg/L, was used. RESULTS: All Binet A patients had normal sTfR values (1.34+/-0.2 mg/L), TfR-F-Index (0.67+/-0.2) and a CRP-adjusted TfR-F-Index. In Binet B and C, sTfR and the TfR-F-Index were significantly increased compared to Binet A patients (p<0.0001). The differences between Binet B and C were not significant. sTfR was increased in 85%, TfR-F-Index in 46% and the CRP-adjusted TfR-F-Index in 54% of the Binet B patients, in Binet C patients, 80%, 50% and 60% showed increases, respectively. sTfR and the TfR-F-Index decreased or even normalized following successful treatment. CONCLUSIONS: Similar to sTfR, the TfR-F-Index is strongly associated with tumor burden in patients with CLL. Thus, these parameters do not allow for a reliable diagnosis of ID in this patient group.