Objective: To investigate the effect of temperature and protease inhibitor on adrenocorticotrophin (ACTH) stability.
Methods: We collected blood specimens from 10 donors into K3 EDTA (ethylenediaminetetraacetic acid) and K3 EDTA + aprotinin tubes. Plasma specimens were held at room temperature and at 2 °C to 8 for 0, 2, 4, 8, 24, and 72 hours. ACTH concentrations in 4 storage conditions were compared with repeated-measures analysis of variance (ANOVA) at each time point.
Results: ACTH concentrations substantially decreased after a 72-hour time period. At the 72nd hour, standard EDTA tubes and EDTA + aprotinin tubes stored at 4 showed the optimal stability. EDTA + aprotinin tubes stored at room temperature performed more strongly than standard EDTA tubes stored at room temperature.
Conclusion: Our results show that refrigerated storage is more effective than protease inhibitor addition to maintain ACTH stability. We recommend using aprotinin tubes, especially for specimens standing at room temperature.