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Liver
Alkaline phosphatase (ALP)
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A group of isoenzymes from liver (biliary canalicular membrane), bone, intestine and placenta. In adults, raised values point mainly to cholestasis or increased bone turnover.
Reference interval
| Conventional (U/L) | SI (U/L) | |
|---|---|---|
| Adults | 40–129 U/L | 40–129 U/L |
Specimen: Serum or heparinised plasma · Conventional × 1 = SI
Causes of high values
Cholestasis (extrahepatic obstruction, primary biliary cholangitis, primary sclerosing cholangitis), infiltrative liver disease, Paget disease of bone, bone metastases, osteomalacia, hyperparathyroidism, healing fractures, pregnancy (third trimester), growth in childhood.
Causes of low values
Hypophosphatasia, zinc or magnesium deficiency, severe malnutrition, hypothyroidism, after cardiac surgery or massive transfusion.
Pre-analytical and method notes
Values are markedly higher in children and adolescents and rise in late pregnancy. GGT or 5′-nucleotidase helps to show whether a raised ALP is of hepatobiliary origin; isoenzyme electrophoresis is an alternative. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Loscalzo J, et al.. Harrison's Principles of Internal Medicine. McGraw-Hill, 21st edition (2022) — Tier 3 (textbook)
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