Contemporary Issues in Thyroid Disease Measurements

Carole A. Spencer MT, PhD, FACB

July 2009

  Q&A Archive



Over the last forty years, thyroid testing has evolved from manual isotopic tests performed in specialized laboratories to automated nonisotopic measurements made in routine clinical chemistry laboratories. Despite improvements in sensitivity and specificity, a number of technical issues still negatively impact the accuracy and interpretation of thyroid testing in clinical practice. 

1) The diagnostic sensitivity of TSH measurement has been maximized by improved sensitivity, however, controversy remains regarding the setting of the TSH upper reference limit and the clinical significance of mild subclinical hypothyroidism.

2) When binding proteins are grossly abnormal, free T4 immunoassays can be unreliable. Therefore,  direct FT4, total T4, or a free T4 index approach is preferred.

3) Thyroid autoantibody methods for TRAb, TPOAb and TgAb have different clinical utilities as well as qualitative and quantitative differences between different methods that preclude switching assays for serial monitoring.

4) More sensitive 2nd generation (2G) thyroglobulin (Tg) assays are beginning to replace 1st generation assays for managing patients with differentiated thyroid cancers. In the future, trends in serial 2G Tg measurements will replace the need for expensive recombinant human TSH-stimulated Tg testing.

This presentation will discuss these issues relative to the use of these tests in clinical practice.



Dr. Carole Spencer received a 1st. Class Bachelor of Science degree in Applied Biochemistry from Bath University of Technology in England, U.K., and later a PhD from the Department of Medicine at Glasgow University, Scotland, U.K. In 1977, she immigrated to the United States and joined the University of Southern California in Los Angeles.  

Dr. Spencer holds the rank of Professor of Medicine in the Department of Medicine at USC, where she is a licensed Medical Technologist, and directs the USC Endocrine Laboratories. Her research career has focused on the clinical and laboratory aspects of thyroid disease and treatment, and she has authored or co-authored more than 80 original papers, chapters and monographs on the clinical and laboratory aspects of thyroidology.
Dr. Spencer is a past President of the American Thyroid Association and a member of the ATA Laboratory Services Committee. She is the recipient of numerous outstanding speaker awards from the American Association for Clinical Chemistry, and she received the 2004 Distinguished Scientist Award from the National Academy of Clinical Biochemistry.  

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