Comparison of stability of PTH in serum and in EDTA plasma

Aim: to determine the mean difference in concentration of pth in edta plasma and serum at room temperature (22°c). design: randomized control trial. setting: department of chemical pathology,quaid-e-azam medical college bahawalpur. methods: 560 volunteers were randomly divided into two groups a and b. to group a blood sample edta was added,whereas,blood samples from group b were analyzed without adding edta. about 10 ml of blood was drawn from each patient and serum was separated with in 30 min by centrifuge machine. the serum was then divided into three aliquots,to be analyzed as base line reading and at 24 and 72hrs. results: samples without preservative showed statistically significant decrease in pth concentration from baseline after 24hrs (p value< 0.0001) and at 72hrs (p=0.0001). whereas the edta samples were stable at 24 hrs (p=0.32) and 72 hrs (p=0.64). conclusion: use of edta plasma for pth measurement greatly increases pth stability even at room temperature.