Alkaline phosphatase (ALP) - plasma or serum

Last updated: Thursday, 18, March, 2004

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Item Process
Specimen

5 mL blood in lithium heparin or plain tube.

Method

Spectrophotometry.

Reference Interval

Neonate: 50-300 U/L
Growing child: 70-350 U/L
Adult, non-pregnant: 25-100 U/L

Higher levels are seen in the third trimester of pregnancy and in individuals over 50 years of age.

Application

Investigation of hepatobiliary or bone disease.

Interpretation

Increased levels in liver disease (particularly in association with cholestasis), bone disease (with increased osteoblastic activity eg, Paget’s disease), some bony metastases (especially prostate and breast), and at times in malignancy without liver or bone metastases (Regan isoenzyme).

May also be elevated in some gastrointestinal diseases or due to a macroenzyme.

Alkaline phosphatase isoenzymes are rarely necessary to identify the source of an elevated ALP.

Marked but transient elevation of ALP may be seen in children, probably attributable to viral infection.

Abnormal dentition and fragile bones with decreased ALP characterise the autosomal recessive disease hypophosphatasia.

Reference

Rochling FA. Clin Cornerstone 2001; 3(6): 1-12.