Alkaline phosphatase (AP, ALP) belongs to a group of isoenzymes (liver AP, bile duct AP, bone AP (bone-specific also ostase), and small intestine AP) that accompany many different metabolic processes in the body. Since alkaline phosphatase is increasingly released into the blood during cholestasis (bile stasis), this laboratory parameter also belongs to the cholestasis enzymes. However, for differential diagnosis, the activity of other cholestasis enzymes that may not also be of osteogenic origin (eg, γ-GT (synonyms: γ-GT (gamma-GT) or indirect bilirubin) must be determined.
The procedure
Material needed
- Blood serum
Preparation of the patient
- Not necessary
Disruptive factors
- Avoid hemolysis (dissolution of red blood cells)! This leads to a decrease in alkaline phosphatase in case of severe hemolysis.
Normal values for children – old reference range
| Age | Normal values in U/L (old reference range) |
| <10th day of life (LT) | 110-450 |
| 10TH-30TH LT | 110-580 |
| 1-6 months of age (LM) | 140-720 |
| 6TH-12TH LM | 120-700 |
| 12TH-18TH LM | 110-650 |
| 19-24 LM | 110-590 |
| 2nd-9th year (LY) | 110-500 |
| 9TH-15TH LJ | 130-700 |
Normal values for children – new reference range
| Age | Normal values in U/L (new reference range) |
| 1. LT | < 250 |
| 2ND-5TH LT | < 231 |
| 6.LT- 6. LM | < 449 |
| 7TH-12TH LM | < 462 |
| 1-3RD LJ | < 281 |
| 4TH-6TH LJ | < 269 |
| 7-12 LJ | < 300 |
| 13-17 LJ ♀ | < 187 |
| 13-17 LY ♂ | < 390 |
Normal values women
| Age | Normal values in U/l (old reference range) | Normal values in U/l (new reference range) |
| <50th LYor standard weight | 55-147 | 35-104 |
| > 50th LYorOverweight | 60-170 | 35-104 |
Normal values men
| Normal values in U/l (old reference range). | Normal values in U/l (new reference range) |
| 70-175 | 40-104 |
Indications
- Suspected liver disease
- Suspicion of bone changes such as bone metastases
- Suspicion of osteoporosis or osteomalacia (softening of the bones).
Interpretation
Interpretation of elevated values
Hepatic causes
- Acute hepatitis (inflammation of the liver).
- Cholangitis (bile duct inflammation)
- Cholestasis (bile stasis)
- Cholecystitis (gallbladder inflammation)
- Chronic hepatitis (inflammation of the liver)
- Liver metastases
- Liver tumors
- Liver cirrhosis – connective tissue remodeling of the liver with resulting functional impairment.
- Primary sclerosing cholangitis (PSC) – chronic inflammation of the extra- and intrahepatic (located outside and inside the liver) bile ducts.
- Toxic/drug-induced liver injury (see “Hepatotoxic drugs” below.
- Congestive liver
- Steatosis hepatis (fatty liver)
Endocrine causes
- Acromegaly – enlargement of the body end limbs after the end of growth usually due to brain tumors.
- Hypovitaminosis D (deficiency of vitamin D; eg, osteomalacia).
- Hyperparathyroidism (parathyroid hyperfunction).
- Cushing’s disease – disease in which too much ACTH is produced by the pituitary gland, resulting in increased stimulation of the adrenal cortex and, as a consequence, excessive cortisol production.
Gynecological causes
- Pregnancy (3rd trimester/third trimester): physiological.
Osseous (bone-related) causes.
- Fractures (bone fractures)
- Bone metastases (osteoclastic; osteoclasts → osteolysis/bone dissolution).
- Bone tumors such as osteosarcoma.
- Paget’s disease (ostitis deformans) – bone disease associated with greatly increased bone remodeling.
- Osteomalacia (bone softening)
- Osteoporosis
- Renal osteodystrophy – bone changes that occur in chronic renal failure.
Medication causes
- Antiepileptic drugs
- Chlorpromazine
- Hormones
- Progestins
- Estrogens
- Thiamazole
Other causes
- Renal insufficiency
- Renal cell carcinoma (kidney cancer)
- Pancreatic cancer (pancreatic cancer – idiopathic elevated alkaline phosphatase may be an early alarm sign of pancreatic cancer.
- Sarcoidosis – systemic disease primarily affecting the lymph nodes and lungs.
Interpretation of decreased values
- Anemia (anemia)
- Achondroplasia – hereditary disease that causes short stature and deformities such as bone bending.
- Protein deficiency (protein deficiency)
- Hypothyroidism (underactive thyroid gland)
- Hypophosphatemia (phosphate deficiency)
- Hypophosphatasia
- Pituitary dwarfism – caused by a disorder in the pituitary gland (pituitary gland).
- Zinc deficiency
Other notes
