Assessment of thyroid function in intensive care unit patients by liquid chromatography tandem mass spectrometry methods

Abstract

Objectives Patients with non-thyroidal illness syndrome have many abnormalities in thyroid hormone tests. Such patients have medical comorbidities associated with low serum proteins and are on multiple medications that interfere with thyroid hormone measurement by immunoassay platforms. It is unknown if these thyroid hormone measurements reflect physiologic conditions or if they are artifacts of testing methodology. Methods Fifty patients were selected from the intensive care unit (ICU) from our institution. Total and free thyroid hormones in plasma were measured by gold standard liquid chromatography-tandem mass spectrometry (LC-MSMS). The results were compared to the Roche Cobas 6000. Patient medical comorbidities and binding protein levels were assessed. Results Concentrations of total 3,5,5'-triidothyronine (TT3) and total thyroxine (TT4) were significantly more likely to be low by LC-MSMS compared to immunoassay. Free 3,5,5'-triidothyronine (FT3) levels were similar by immunoassay and LC-MSMS. However, FT4 concentrations were mildly elevated for many patients when measured by ultrafiltration LC-MSMS (19/50, 38%) compared to 1/50 (2%) when measured by immunoassay (p = 0.0001). Decreased albumin and thyroxine binding globulin were common and patients were on an average of 11.7 ± 5.0 medications, all factors known to interfere with results found on immunoassays. Conclusions Marked discrepancies in thyroid hormone measurement were noted between reference LC-MSMS and a common immunoassay platform. It is hypothesized that T4 binding to low affinity albumin is displaced by several drugs, raising concentrations of FT4 by LC-MSMS compared to immunoassay, and that the immunoassay values are falsely decreased due to low binding proteins in our patient population.

3,5-T2—A Janus-Faced Thyroid Hormone Metabolite Exerts Both Canonical T3-Mimetic Endocrine and Intracrine Hepatic Action

“…However, various practical and technical issues related to above-mentioned challenges of TH physiology and pathophysiology hampered rapid progress and success in quantification of total and free THM concentrations. While meanwhile several laboratories developed procedures to accurately determine total T4 and total T3 in human plasma or serum and largely agree on concentrations ranges (25,(67)(68)(69)(70)(71)(72)(73), this consensus has not been achieved yet for most of the other TH metabolites, which occur at much lower concentrations. Analytical procedures typically work well with buffer solutions, in vitro reaction mixtures, as well as with samples of "simple" matrix composition, while reported concentrations in human or experimental animal serum, plasma, and tissue show wide variations and marked insufficiencies in terms of method validation, standardization, and quality assessment parameters [see (23,24,74)].…”

A direct comparison of liquid chromatography-mass spectrometry with clinical routine testing immunoassay methods for the detection and quantification of thyroid hormones in blood serum

“…The developed method reduces the run time from 14 to 5 min and as an isocratic method it removes the need for column re-equilibration in between samples. The method also shows improvements over those previously published in terms of precision, extraction recoveries and correlation [ 32 – 35 ]. Tanoue et al [ 35 ] reported extraction recoveries, for low concentration, 82.9, 81.9, 83.5 and 62.7% and for high concentration, 86.9, 90.5, 90.0 and 69.6% for T4, T3, rT3 and T2, respectively.…”

“…There are a number of papers documenting the development and comparison of LC-MS methods for the analysis of thyroid hormones, utilising positive ionisation. These include the thyroid hormones T4 and/or T3 [ 32 – 34 ] as well as rT3 and T2 [ 35 ]. Typical sample preparation extraction recoveries, for the thyroid hormones, ranged between 62.7 and 114% with a coefficient of variation of 1.8–31% and precision between 3.8 and 12% [ 35 ].…”

“…Typical sample preparation extraction recoveries, for the thyroid hormones, ranged between 62.7 and 114% with a coefficient of variation of 1.8–31% and precision between 3.8 and 12% [ 35 ]. Correlation between LC-MS and immunoassay methods, resulting in r 2 values between 0.30 and 0.90 [ 32 – 35 ]. To be able to accurately measure T3 levels, in blood serum, it is necessary to ensure that rT3 does not skew the data.…”

Low Value of Thyroid Testing in the Pediatric Inpatient Setting

“…Another possibility is that our method for FT4, which is equilibrium dialysis-tandem mass spectrometry, has been found to be less affected by the metabolic changes of acute illness, including low-binding proteins, than older immunoassay methods for measuring FT4. 9 Another potential cause of low FT4 with nonelevated TSH is hypopituitarism, and thyroid testing is appropriate when there is clinical suspicion of that diagnosis, such as detection of an ectopic posterior pituitary on MRI. Although testing for possible hypopituitarism was done in 29 children, no cases of low FT4 due to a new diagnosis of hypopituitarism were identified.…”