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Submitted on behalf of Dr. Michael Abraham
Thyrotropin (TSH)
- Different types of test available:
- The first tests available were radioimmunoassay.
- The next type of test available is the immunometric test.
- As each test is developed there has been a trend to use the term ‘generation’ for a 10 fold increase in sensitivity. 1
- Indications for ordering in the ED: Hypothyroidism, Graves Disease, Hashimoto’s Thyroiditis, Thyroid storm.
- Diagnostic Accuracy
- The original TSH benchmark was the ability to measure euthyroid (0.4 – 4mIU/L) from very low (<0.01 mIU/L) which is suggestive of Graves disease.
- Most new tests have a functional sensitivity of <0.02mIU/L.
- The clinical sensitivity and specificity have to be determined by each laboratory’s staff. This requires testing of samples over a 6-8 week period as should include a sample of the population that is being tested.2
- Average turnaround time to complete test:
- The tests are mainly run on large lab analyzers. There are many commercially available tests the turnaround time is dependent on the manufacturer of the machine.
References
1. Spencer CA, Takeuchi M, Kazarosyan M. Current status and performance goals for serum thyrotropin (TSH) assays. Clin Chem. Jan 1996;42(1):140-145.
2. Liebert M. Thyrotropin/Thyroid Stimulating Hormone (TSH) Measurement. Http://www.medscape.com/