ALKALINE PHOSPHATASE (ALP) - plasma or serum

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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, esp prostate and breast) and at times in malignancy without liver or bone metastases (Regan isoenzyme). 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: Walmsley RN et al. Cases in Chemical Pathology. 2nd ed. PG Publishing 1988.

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