Farooq Ahmad Khan, Asma Shaukat, Sameena Ghayur.
Effect of Storage Temperature, Duration and added Preservative on estimation of Serum Cortisol.
J Coll Physicians Surg Pak Jan ;11(12):762-4.

Objective: To determine the effects of temperature and duration on the stability of cortisol measurement as well as to ascertain the role of citric acid as preservative. Design: Prospective experimental study. Place and duration of Study: The study was conducted at Armed Forces Institute of Pathology, Rawalpindi, from July 1995 to September 1996. Subjects and Methods : Blood samples were collected from 58 healthy volunteers and stored at different temperature (room temperature, 4oC and -20oC), for various lengths of time (24 and 72 hours), with or without citric acid as preservative. Serum Cortisol assay was performed using chemiluminiscent immunoassay technique. Results were compared using Wilcoxan Paired Signed Rank test. Results : Cortisol assays showed stable results when the samples were stored at 4oC or –20oC with or without citric acid as preservative. Samples kept at room temperature for 72 hours only showed stability when the samples contained citric acid as preservative. Conclusion : Blood samples for cortisol measurement should be taken in containers having citric acid as preservative. If samples are kept at room temperature for 72 hours, there is significant decrease in the value of cortisol measured. Blood samples can be stored at 4oC for analysis up to 72 hours. For storage beyond 72 hours, storage at –20oC is recommended.

PakMediNet -Pakistan's largest Database of Pakistani Medical Journals - http://www.pakmedinet.com