Spuriously high serum concentrations of TSH due to the use of an automatic pipetting device

Abstract

In a clinically hyperthyroid patient a TSH-value of 0.75 mU/L was measured. Upon retesting TSH was <0.1 mU/L. The patient's sample initially had been preceded, in the pipetting device, by a grossly hypothyroid patient's sample. Analogous problems were subsequently documented in 10 cases when samples of other hyperthyroid patients were preceded by samples with modestly to markedly elevated TSH. The spurious elevation of TSH (0.12 to 1.18 vs. <0.1 mU/L) appears to be due to a carryover effect from the respective previous sample within the used automatic pipetting system. This carryover was much larger than previously suggested, and occurred unpredictably.

Anti-ruthenium antibodies mimic macro-TSH in electrochemiluminescent immunoassay

“…Inappropriate TSH concentrations with normal FT 4 ("funny TFT") [12] are a frequent occurrence [2,3,12] and have been termed "syndrome of inappropriate secretion of thyrotropin" [31]. If subclinical hypothyroidism, poor compliance with thyroxine, malabsorption of thyroxine, drug effects (e.g., amiodarone), non-thyroidal illness (NTI) recovery phase and TSH resistance are excluded or unlikely, as in our patient, assay interferences have to be considered [12].…”

“…Due to its prime role in thyroid regulation and its large dynamic range, thyroid stimulating hormone (TSH) represents the most important and most frequently ordered screening parameter for the evaluation of thyroid function [1][2][3]. However, TSH is only reliable when the hypothalamic-pituitary-thyroid axis is intact and possible central hypo-or hyperthyroidism are ruled out, drug effects and rare diseases can be excluded and TSH determinations are analytically correct [3,4].…”