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Quantitative method for determining serum alkaline phosphatase isoenzyme activity: estimation of intestinal component
M J Peake1, M Pejakovic, G H White
1Department of Biochemistry and Chemical Pathology, Flinders Medical Centre, Bedford Park, South Australia.
Journal of Clinical Pathology
|February 1, 1988
Summary
Levamisole inhibition offers a superior method for measuring intestinal alkaline phosphatase (IAP) activity compared to L-phenylalanine. This new assay demonstrates improved precision and accuracy for IAP determination in clinical samples.
Area of Science:
- Biochemistry
- Clinical Chemistry
- Enzymology
Background:
- Alkaline phosphatase (ALP) is a crucial enzyme with various isoenzymes, including intestinal alkaline phosphatase (IAP).
- Accurate measurement of IAP is vital for diagnosing and monitoring conditions affecting the gastrointestinal tract.
- Existing methods for IAP quantification have limitations in specificity and precision.
Purpose of the Study:
- To evaluate the efficacy of levamisole inhibition as a method for measuring intestinal alkaline phosphatase (IAP) activity.
- To compare the performance of the levamisole inhibition assay with the traditional L-phenylalanine inhibition method.
- To assess the precision and accuracy of the levamisole-based assay for IAP quantification.
Main Methods:
- Intestinal alkaline phosphatase activity was measured using levamisole inhibition in a 2-amino-2-methyl-1-propanol (AMP) buffer system.
- Results were compared against a previously established method utilizing L-phenylalanine inhibition.
- Assay imprecision was determined using standard deviation (SD) for specimens with varying total alkaline phosphatase activity.
Main Results:
- Levamisole inhibition demonstrated high specificity, retaining 62% intestinal ALP activity while significantly inhibiting other isoenzymes.
- The levamisole assay exhibited superior precision (SD = 0.6 U/l) compared to the L-phenylalanine method (SD = 3.9 U/l) for samples below 250 U/l.
- Levamisole inhibition resulted in smaller errors and more accurate recovery of IAP activity, especially in serum pools with elevated ALP levels.
Conclusions:
- An assay based on levamisole inhibition provides a more accurate and precise measure of intestinal alkaline phosphatase activity than the L-phenylalanine method.
- Levamisole inhibition is recommended for routine clinical use due to its improved performance in quantifying IAP.
- This optimized assay enhances diagnostic capabilities for conditions related to intestinal alkaline phosphatase.