Disorders of thyroid metabolism affect millions of patients worldwide. Clinical diagnosis and treatment requires testing and monitoring of patient thyroid hormone levels. Reference ranges for thyroid hormones vary among patient sub-groups and disease states. Triiodothyronine (T3) and thyroxine (T4) are the most commonly tested thyroid hormones. Reverse triiodothyronine (rT3) is an inactive isomer of T3 formed primarily by enzymatic de-iodination at the 5-position of Thryoxine (T4).1 Currently most thyroid hormone assays are by radioimmunoassay (RIA) which can be expensive, have limited shelf life, and lack specificity.1 The available RIA assay for rT3 is designated for research use only in the USA.2 There is a significant clinical diagnostic need for robust and accurate methods for determining thyroid hormone levels in general and particularly for rT3. In recent years there has been significant push to develop LC/MS/MS methods for quantitation of thyroid hormones with the potential for higher accuracy even on the low end, better specificity, and the ability to quantitate the different thyroid hormones separately.
Calibrators for LC/MS/MS methods are critical to accuracy of results and must be carefully evaluated. The importance of proper selection and certification of materials and their impact on calibrator accuracy and resulting clinical decisions is illustrated in this poster with rT3. rT3 was developed as a certified solution reference standard and evaluated at Cerilliant and LabCorp, demonstrating the impact of calibrator certification on clinical reference ranges.
References
1. Wang, Dongliand Stapleton, Heather M., Analysis of Thyroid Hormones In Serum by Liquid Chromatography-Tandem Mass Spectrometry, Anal BioanalChem. 2010 July; 397(5): 1831–1839.
2. ALPCO reverse T3 RIA Product Literature