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Persistent problems with the specificity of immunometric TSH assays
1Department of Internal Medicine and Endocrinology, Aalborg Hospital, Denmark.
Thyroid : Official Journal of the American Thyroid Association
|January 1, 1993
Summary
Sensitive thyroid-stimulating hormone (TSH) assays can still produce inaccurate results. Nonspecific TSH values in hyperthyroid patients may mimic normal thyroid function, requiring careful interpretation of test results.
Area of Science:
- Clinical chemistry
- Endocrinology
- Immunoassay development
Background:
- Sensitive immunometric assays for thyroid-stimulating hormone (TSH) are standard for thyroid function testing.
- Previous concerns about heterophilic antibodies causing falsely high TSH values are thought to be resolved by assay modifications.
Purpose of the Study:
- To evaluate the continued potential for nonspecific results in current sensitive TSH assays.
- To assess the impact of nonspecific TSH values on the diagnosis of hyperthyroidism.
Main Methods:
- Evaluation of six different TSH assays using sera from 63 patients with untreated hyperthyroidism (Graves' disease and Plummer's disease).
- Analysis of TSH values, including testing with thyrotropin-releasing hormone (TRH) stimulation and addition of mouse serum.
Main Results:
- Despite using suppressed TSH values in at least one assay, many sera yielded measurable TSH levels in others.
- Eleven sera showed TSH values above 0.10 mU/L in at least one assay, with six above 0.40 mU/L.
- Nonspecific TSH values varied across assays and were not altered by TRH stimulation or mouse serum addition.
Conclusions:
- Measurable serum TSH does not always exclude primary hyperthyroidism.
- Nonspecific TSH values are a common cause of non-suppressed TSH in hyperthyroidism and should be considered before rarer causes.
- Current TSH assays may still produce nonspecific results, impacting diagnostic accuracy.