Stability of Anti-thyroid Stimulating Hormone Receptor Antibody in Whole Blood and Serum: Caution Required for Reflective and Batch Testing.

Introduction: Anti-thyroid stimulating hormone receptor antibody (TRAb) stability is stated as 7h at 20-25°C in the Roche Elecsys assay kit insert. The purpose of this study was to determine TRAb stability in whole blood and serum to assess the suitability of samples for reflective and weekly batch testing (with a single freeze-thaw cycle).

Methods: In the first study, blood from = 5 volunteers was used to assess: (1) stability in whole blood at room temperature up to 24h, and (2) stability in serum at 4-8°C up to 72h. In the second study, = 21 patient samples were analysed in serum stored at 4-8°C for two and five days post-preliminary analysis.

Results: There was a statistically significant decrease in TRAb concentration caused by the single freeze-thaw cycle of -8.9% ± 5.2% ( = 0.03). TRAb concentration decreased in whole blood between 0 and 24h by -16.5% ±9.2%, and declined in serum over time by -11.6% ±6.6% (at 12h). In the patient samples, serum TRAb concentration decreased over time by -4.6% ± 2.5% at day two and -6.5% ± 4.0% at day five.

Conclusion: TRAb concentration decreases over time in both whole blood at room temperature and serum samples stored at 4-8°C. A single freeze-thaw cycle also has a statistically significant effect on TRAb concentration.