Spuriously High Free Thyroxine Values in Familial Dysalbuminemic Hyperthyroxinemia

[摘要] To the Editor:Cartwright et al. recently showed that current commercially available free thyroxine (FT4)1 methods yield spuriously high results in individuals with familial dysalbuminemic hyperthyroxinemia (FDH) (1). In particular, variants of the “one-step labeled analog” technique have been notorious in this respect, whereas the 2-step approach, in which the sample is washed away before the antibody-bound T4 is brought into contact with the labeled T4 analog, is thought to eliminate the problem of tracer binding to albumin and especially albumin in FDH patients. Some 2-step assays, however, also yield spuriously high values in individuals with this condition; thus, interference is not simply a problem of 1-step assays. Inhibitors of T4 and T4 analog binding to the albumin included in the incubation buffer have been suggested to play a role for both the 1- and 2-step designs. In addition, the report of Cartwright et al. referred to similarly increased results obtained by symmetric dialysis when the incubation buffer of the Beckman Coulter Access 2-step assay (known to give falsely increased results for FDH samples) was used. We …

[学科分类] 过敏症与临床免疫学