Impact of preanalytical factors on the stability of acetylcholine receptor antibodies in serum

This study investigated the preanalytical stability of acetylcholine receptor antibodies (AChRAb) in patient samples, a crucial biomarker for diagnosing Myasthenia Gravis (MG). The objective was to evaluate the impact of delayed centrifugation, storage temperature, and repeated freeze-thaw cycles on the accuracy of AChRAb test results. Blood samples were collected from nine MG patients, and four stability studies were conducted. These studies examined: (I) the effect of delayed centrifugation on whole blood (up to 7 h at room temperature), (II) storage of serum at room temperature (up to 7 days), (III) storage of serum at -20 °C (up to 26 weeks), and (IV) the impact on serum of repeated freeze-thaw cycles (up to 3 cycles). AChRAb levels were measured using ELISA, and the results were analysed for statistical variation against baseline measurements using bias limits of ±15%. The findings revealed that AChRAb remained stable for up to 7 hours of delayed centrifugation, 5 days at room temperature, 13 weeks at -20 °C, and after 3 freeze-thaw cycles. However, the antibody levels showed instability after 7 days at room temperature and 26 weeks at -20 °C, where the percentage differences exceeded acceptable limits. Analytical variation, especially at low antibody levels, and differences between ELISA kit lots were potential factors contributing to these findings. In conclusion, AChRAb shows good stability if care is taken to avoid prolonged storage and handling times to maintain diagnostic accuracy.