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Thyroid Stimulating Hormone
|Test Update Information||Effective 03/19/2013, the platform used for the TSH assay has changed from the Siemens DPC Immulite to the Beckman UniCel DxI 600. This assay change has little or no effect on the assay results.|
|Clinical Questions||Does my patient have autoimmune thyroiditis?|
|Test group||Thyroid tests|
|Performed by||Parnassus Chemistry|
|In House Availability||Test available 24 hours per day 7 days per week|
|Method||Immunochemiluminescent (Beckman DxI600)|
|Container type||Gold top or Light Green top|
|Amount to Collect||1.6 mL blood|
|Sample type||Serum or heparinized plasma|
|Preferred volume||0.8 mL serum or heparinized plasma|
|Min. Volume||0.5 mL serum or heparinized plasma|
|Normal range||0.45-4.12 mIU/L|
|Turn around times||4 hours|
|Additional information||The low end functional sensitivity (20% coefficient of variation cutoff) for this assay is 0.02 - 0.03 mIU/L. Reference ranges were adopted from NHANES III and verified in 170 adult blood donors negative for anti-TPO and anti-thyroglobulin antibodies (Hollowell JG et al. Serum TSH, T4, and thyroid antibodies in the United States population ,1988 to 1994: National Health and Nutrition Examination Survey , NHANES III. J Clin Endocrinol Metab 87:489–499, 2002. Garber JR et al. Clinical Practice Guidelines for Hypothyroidism in Adults: American Association of Clinical Endocrinologists and the American Thyroid Association, Thyroid 12:1200-1235, 2012).
In pregnant subjects, TSH levels decline in the first trimester and then rise after 10 -12 weeks gestation. The upper limit of normal is 2.5 mIU/L in the first trimester, 3.0 in the second trimester, and 3.5 mIU/L in the third trimester. The lower range of normal for TSH in pregnancy is 0.1 – 0.2 mIU/L lower than the normal range of non-pregnant subjects (Garber JR et al. Clinical Practice Guidelines for Hypothyroidism in Adults: American Association of Clinical Endocrinologists and the American Thyroid Association, Thyroid 12:1200-1235, 2012).
Neonatal and cord blood levels are 2-4x higher than levels at ≥ 2 weeks of age through adult life. Neonatal levels are also screened by the State program.
|Medical Necessity?||Yes. Click here for more information|
|Last Updated||10/15/2014 11:53:11 AM|
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