Abstract

QuantifÏcation of the soluble transferrin receptor (sTfR) in serum is a useful tool for estimation of the body iron stores and iron distribution. The objective of our study was to evaluate the analytical performance of three commercially available immunoassays for the determination of sTfR in serum and to define reference ranges for this parameter. We evaluated the "Quantikine^TMIVD^TM sTfR" enzyme-immunoassay by R&D Systems (Wiesbaden, Germany), the "IDEA^TM sTfR IEMA" immunoassay by Orion Diagnostica (ADL-Wallac-GmbH, Freiburg, Germany) and the "N Latex sTfR" assay, a fully mechanized particle-enhanced immunonephelometric test by Dade-Behring (DB) (Liederbach, Germany). Both the assays by R&D systems and by Dade-Behring are calibrated against the transferrin receptor isolated from a pooled human plasma preparation, whereas the Orion test calibrator is a preparation from human placenta. Results were reported in nmol/L for the R&D test and in mg/L for the Orion and the DB tests. Coefficients of variation for day-to-day precision were 7.1 - 7.4% at a concentration of 11.8 - 31.1 nmol/L for the R&D assay, 15.0% (2.0 - 6.0 mglL) for the Orion assay, and 2.3 - 4.3% (0.96 - 1.71 mg/L) for the DB-test. Recovery in spiked samples varied from 87 to 119% (R&D), 81 - 90% (Orion) and 100 - 109% (DB). The lower detection limit was below 1.0 nmol/L (R&D) or below 0.23 mg/L (Orion) and 0.10 mg/L (DB), respectively. The reference population consisted of 101 apparently healthy subjects without clinical or laboratory evidence of anemia, latent iron deficiency or acute phase response. Analysis of serum samples revealed the following reference ranges: 11.3 - 31.0 nmol/L (0.83 - 2.29 mg/L) for "Quantikine^TMIVD^TM sTfR", 1.4 - 5.5 mg/L for "IDEA^TM sTfR IEMA" and 0.81 - 1.75 mg/L for "N Latex sTfR". Differences in the reference intervals and poor comparability of the test results are due to divergent standardization.

DOI: Clin. Lab.1999;45:295-304