Effect of incubation period on measurement of alkaline phosphatase enzyme activity at 37°C

Background: Laboratory analysis of alkaline phosphatase (ALP) from blood can detect abnormalities which reflect changes in certain health conditions, including liver disease and bone disease. Despite the importance of measuring different isoenzymes activity in different diseases, total ALP test is often requested, which is not specific to identify the type and the extent of tissue damage. ALP activity measurement at different incubation period may affect the actual measurement as ALP is a heat labile enzyme and specific ALP isoenzymes have different sensitivity to heat inactivation which creates lab to lab variability and significant change if particular isoenzyme is predominant in patient’s sera. Objectives: The study was performed to measure the loss of activity of ALP at different 37°C incubation periods during ALP measurement in serum. Materials and Methods: Quality control materials were analyzed for ALP enzyme activity in 2-amino, 2-methyl, 1-propanol buffer, and 4-nitrophenyl phosphate substrate with different incubation periods. Result: There is a gradual decrease in enzyme activity on increase of incubation period. Conclusion: The effect of incubation period on ALP activity measurement at 37°C may be clinically relevant if one of the isoenzymes is predominant in the patient sera.