In fact, third-generation
TSH assays may present more problems than the old [T.sub.4] and [T.sub.3] tests ([T.sub.4] and [T.sub.3] uptake).
The results from this method comparison study suggest that a practical approach to harmonization of
TSH assays could be to establish traceability of calibration to the mean values for a panel of serum samples.
A false-negative value can be seen, however, when the interfering antibodybinds to 1 of the 2 antibodies in a noncompetitive assay (6), as in the Roche Elecsys
TSH assay.
The interference seen with the
TSH assays (Bioclone Elegance, Dade Befiring Dimension, Abbott AxSYM, DPC 1MMULITE, and Beckman DxI assays) in samples from our patients appears to have been transmitted transplacentally from the mother's blood.
Evaluation of the analytical and clinical performance of a third generation
TSH assay on Bayer Advia Centaur analyzer [Abstract].
The ADVIA Centaur method did not meet the definition of a third-generation
TSH assay because the TSH concentration at which it had a CV of 20% was 0.039 mIU/L and not <0.02 mIU/L.
The detection limits correspond to those for the fourth- and third-generation
TSH assays. The large dynamic range well below and above the reference interval for TSH (~0.5 to 5.0 mIU/L) (9,10) allows detection of hypo- as well as hyperthyroidism.
In an attempt to avoid such interference, Roche Diagnostics have used in their
TSH assay "special interference-eliminating" reagents and a chimeric antibody (2).
These data suggest that the IgG[kappa] paraprotein contained within the patient's restricted immunoglobulin peak produced the false-negative results on the Abbott AxSYM
TSH assay. We speculate that the patient's antibody binds to an idiotope on one of the antibodies used in the AxSYM assay and sterically blocks the binding of TSH to that antibody.
Undiluted and diluted TSH results (pIU/mL) on 5
TSH assays from 4 manufacturers.
Now, a team researchers led by Randy Polson, PhD, from the University of Utah has developed a device that uses an iPhone's LED flash, digital camera with collimating lens to optimize illumination and focusing, and a specially-designed app to collect an image of a completed
TSH assays and, and convert the image into a quantitative TSH values.
Free hormone levels are less reliable measures of thyroid function than are
TSH assays because they are more susceptible to factors that can adversely affect test accuracy.
