The Role of Inhibitors in Ascertaining the Type of Isoenzyme of Alkaline Phosphatase (ALP) and its Clinical Correlations

Aims: To estimate the level of Alkaline Phosphatase (ALP) in the serum and to evaluate the role of inhibitors in ascertaining the type of isoenzyme of ALP and further correlation with clinical diagnosis and other biochemical parameters of the patients.

Study Design: Cross Sectional with Diagnostic Accuracy Type

Place and Duration of Study: Department of Biochemistry, Guru Gobind Singh Medical College, Faridkot, October 2017 to October 2018.

Methdology: 250 Patients (143 women and 107 men; age range 19-85 years) with elevated ALP level were enrolled. ALP activity was measured in the serum and isoenzymes were ascertained by using chemical inhibitors i.e. Urea, L-Phenylalanine, Guanidine Hydrochloride, and heat inactivation which inhibit ALP activity. For heat inactivation, serum was incubated at 65°C for 10 minutes. Various other biochemical parameters were estimated for the correlation.

Results: The Mean±SD of ALP level was 373±274 U/L. The percentage of inhibition by Urea, L-Phenylalanine, Guanidine hydrochloride and heat inactivation was 49.5%, 40.5%, 48.6%, and 94.0% respectively in liver disorders, 56.6%, 38.1%, 45.8%, and 89.0% in bone disorders and 29%, 41.6%, 42.8% and 95% in intestinal disorders. The percentage of inhibition in third-trimester pregnant females was 44.4%, 36.8%, 47.1%, and 36.8%, and 51.1%, 47.0%, 50.7%, and 51.2% in preeclampsia. The percentage of inhibition of the Isoenzyme of ALP was according to the type of carcinoma/lymphoma. The correlation of ascertained ALP isoenzyme with AST and ALT is highly significant (P<0.001) in patients of liver diseases. In the patients of Bone disorders the correlation of ALP isoenzyme with Calcium and Phosphorous is also significant (P=0.01 and P=0.01 respectively).

Conclusion: The sensitivity and specificity of this inhibition method to ascertain isoenzymes in raised ALP level was 82.45% and 66.13% respectively. The area under the ROC curve (AUC) is 0.744 which is significant (P<0.0001).