Stability of serum TSH concentration after non refrigerated storage

Background. The ignorance of how sensitive serum samples for defined assays may be, can lead to overprotecting measures. This attitude not only increa ses cost and labor in everyday routine but may be responsible for not evalu ating series of measurements if performed in serum samples not well stored. Methods. Thyrotropin (TSH) concentration in serum was tested in three poole d samples drawn from various patients, before and after four days storage a t freezing (-15 degrees C), low (4 degrees C), and room temperature (18-22 degrees C). TSH concentration was measured in each part, in 22 replicates u sing a commercial assay. Results. The variation of the measured values due to the storage conditions was less than 10%, not exceeding the accepted between assay variation. Conclusions. For the estimation of TSH concentration, patient serum samples may be stored up to four days at 4 degrees C or even at room temperature w ithout significant loss of measurement accuracy.