The Effect of Delay in Serum Separation on the Results of Biochemical Tests

The present study aimed to investigate the effect of delay in serum separation on the results of some biochemical tests, as one of the pre-analytical errors.

In this study, 50 healthy volunteers participated. 12 ml of blood was taken from each person and divided into 6 tubes assigned. In order to separate the serum, one of the samples of each person was centrifuged as a base sample at the standard time (1 hour after blood sampling), and the other samples of that person were centrifuged with a delay of 1,2,3,4 and 5 hours compared to the base sample. The serum from each sample was analyzed for 21 different analytes including blood sugar (BS), blood urea nitrogen (BUN), uric acid (U.A), calcium (Ca), magnesium (Mg), triglyceride (TG), cholesterol (Chol), high-density lipoprotein (HDL), aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), total bilirubin (T.B), direct bilirubin (D.B), albumin (Alb), total protein (TP), amylase (Amy), lipase (Lip), lactate dehydrogenase (LDH) and creatine phosphokinase (CPK).

A significant difference was found between the means of blood sugar (BS) in the elapsed times from the time of blood sampling. The means of BS showed a decrease of 4.78 % on average for each hour of delay in serum separation. In the case of other analytes, no significant difference was observed between their means at each of the time points elapsed since the time of blood sampling.

Considering the significant effect of delay in serum separation on BS test, it is necessary to centrifuge the whole blood sample and separate its serum as soon as possible. In the case of the other investigated analytes, the delay in serum separation up to 6 hours does not have a significant effect on the results.