Evaluation of an ELISA test for determination of the serum transferrin receptor. Demonstration of discordance between results obtained with two methods

Abstract

We undertook this study to evaluate a recently introduced ELISA kit for determining serum transferrin receptor (TfR) concentration (TfR®, Ramco Laboratories, Inc.), to produce reference values for healthy adults, and to compare the results with another commercially available reagent system. The mean (SD) recovery of added TfR was 88% (6%). In dilution studies, the ratio between the measured and expected values was 0.98 (0.11). The intra-assay and interassay coefficients of variation were from 5% to 7% and from 6% to 9% in a physiological and a supraphysiological concentration range, respectively, and from 13% to 16% in a subnormal concentration range. In healthy adults between 20 and 60 years of age, we observed no age- or sex-related differences in TfR values. Thus, the same reference interval, 3.0-8.2 mg l^-1, may be used for this population. The correlation between the results obtained with the Ramco TfR® test and the Amgen Diagnostics ClinigenTM test was satisfactory (r=0.79). The Ramco TfR® test produced higher values (TfR®=0.40 (-0.45-1.25)+1.46 (1.16-1.75)* Clinigen^TM). The number of samples that fell within the same concentration interval with both methods (low, normal or high in relation to the respective reference interval) was only 45% (27/60). The Ramco TfR® test had fewer values falsely suggesting iron deficiency than the Clinigen^TM test. Serum TfR methods need to be uniformly standardized.