Alkaline Phosphatase
Overview
Alkaline phosphatase (ALP) is an enzyme found in various tissues, primarily liver, bone, intestine, and placenta, that catalyzes the hydrolysis of phosphate esters at alkaline pH. It plays a key role in bone mineralization and liver bile processing. Elevated levels may indicate liver disease (e.g., cholestasis, hepatitis), bone disorders (e.g., Paget’s disease, osteomalacia), or pregnancy, while low levels can occur in malnutrition, hypophosphatasia, or zinc deficiency.[ from prior context]Clinical Use Cases
- Differential diagnosis of cholestatic liver disease versus hepatocellular injury.
- Evaluation of bone diseases like Paget’s disease, rickets, or bone metastases.
- Monitoring treatment response in liver or bone conditions.
- Screening for pregnancy-related changes or nutritional deficiencies.
Specimen Types
- Serum.
- Plasma.
- Occasionally urine or amniotic fluid.
Measurement Methods
- Enzymatic colorimetric assay (IFCC method).
- Immunoassays for isoenzyme differentiation.
- electrophoresis for tissue-specific isoforms.
Test Preparation and Influencing Factors
- No fasting required, but avoid after fatty meals for intestinal ALP.
- Medications like anticonvulsants, estrogens, or antibiotics may elevate levels.
- Physiological factors: growth spurts in children, pregnancy (placental ALP).
- Recent fracture, surgery, or menstruation can transiently increase levels.
Synonyms
- ALP.
- Alk Phos.
- Phosphatase, alkaline.
Further Reading
- Alkaline Phosphatase – MedlinePlus;