Multicentre comparison of free thyroid hormones immunoassays: the Immunocheck study

Abstract

The results of our study demonstrate that a large variability in measured values is still present among different free thyroid hormone immunoassays. Indeed, some immunoassays for both FT3 and FT4 measurement showed percent bias values compared to the consensus mean >20%. Laboratories should inform the clinicians about analytical performance and reference limits of the method used. Furthermore, the clinicians should avoid the use of different methods in the follow-up of patients.