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An evaluation of six solid-phase thyrotropin (TSH) kits.
Journal of Clinical Chemistry and Clinical Biochemistry. Zeitschrift Fur Klinische Chemie Und Klinische Biochemie
|August 1, 1985
Summary
This study evaluated six thyrotropin (TSH) test kits, finding that immunometric assays generally offered better precision and sensitivity than radioimmunoassay for diagnosing thyroid conditions. Three immunometric kits effectively distinguished between euthyroid and hyperthyroid patients.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Assay Development and Validation
Background:
- Accurate measurement of thyrotropin (TSH) is crucial for diagnosing and monitoring thyroid disorders.
- Various immunoassay kits exist, including radioimmunoassay (RIA), immunoradiometric assay (IRMA), and immunoenzymometric assay (IEMA), each with potential differences in performance.
- Standardization using international reference preparations is essential for reliable TSH quantification.
Purpose of the Study:
- To objectively evaluate and compare the performance of six commercially available TSH test kits.
- To assess the diagnostic accuracy, precision, and sensitivity of different immunoassay methods for TSH measurement.
- To determine the suitability of these kits for differentiating between euthyroid and hyperthyroid states.
Main Methods:
- Six TSH kits were evaluated: one RIA, three IRMA, and one IEMA, alongside an in-house immunoluminometric assay (ILMA).
- Kit standards were quantified using a standard curve derived from the WHO 68/38 international reference preparation in a thyrotoxic serum matrix.
- A blinded study design was employed, testing samples from blood donors, thyroliberin-test patients, and thyroid outpatients.
Main Results:
- Immunometric assay kits demonstrated statistical differentiation between euthyroid and untreated hyperthyroid patients, though one IRMA kit (Kit F) showed overlap.
- Three immunometric assays exhibited good precision (CV < 5% between 0.5-5 mU/l), while the most complex method had the worst precision.
- The conventional RIA kit (Kit B) was less precise and sensitive than superior immunometric kits at TSH levels below 1 mU/l.
Conclusions:
- Immunometric assay kits are generally superior to RIA for TSH measurement, offering better diagnostic capability for thyroid dysfunction.
- The thyroliberin-test may aid in monitoring pituitary function recovery in treated thyrotoxic patients due to the sensitivity of immunometric assays.
- Kit performance varied, highlighting the importance of method-specific validation and consideration of reference materials used for calibration.