Related Experiment Videos
[False results on elevated triiodothyronine values in radioimmunoassay]
L Skovsted1, J E Hansen, B Nygaard
1Medicinsk endokrinologisk afdeling F. Amtssygehuset i Herlev.
Ugeskrift for Laeger
|October 9, 1995
Summary
Radioimmunoassay (RIA) can falsely elevate triiodothyronine (T3) levels due to interfering substances in serum. A modified assay using ethanol extraction and non-immune rabbit serum accurately measures T3, distinguishing true from false results.
Area of Science:
- Endocrinology
- Clinical Chemistry
- Immunochemistry
Context:
- Radioimmunoassay (RIA) is a common method for measuring thyroid hormones.
- Elevated serum triiodothyronine (T3) can indicate hyperthyroidism, but assay interference can lead to misdiagnosis.
- Previous studies have identified various factors affecting RIA accuracy, including protein binding and heterophile antibodies.
Purpose:
- To report cases of falsely elevated serum triiodothyronine (T3) concentrations in radioimmunoassay (RIA).
- To investigate the cause of interference in T3 RIA assays.
- To develop a modified assay to differentiate true from false T3 values.
Summary:
- Five patients presented with falsely elevated serum triiodothyronine (T3) levels (> 9 nmol/l) by RIA, inconsistent with other thyroid variables and clinical findings.
- Normal T3 non-specific binding excluded abnormal serum protein binding. Ethanol extraction of T3 before RIA normalized values to 2.0-2.4 nmol/l.
- Interference was attributed to substances binding the reagent-antibody, potentially anti-rabbit antibodies. Addition of non-immune rabbit serum normalized T3 values (1.8-2.4 nmol/l), enabling accurate differentiation.
Impact:
- Identifies a specific interference in T3 RIA assays caused by substances binding reagent-antibodies.
- Provides a modified assay protocol (ethanol extraction and non-immune rabbit serum) for accurate T3 measurement.
- Highlights the importance of assay validation to prevent misdiagnosis of thyroid disorders.