ALP is an enzyme that catalyzes the hydrolysis of phosphate esters in an alkaline environment. The ALP test helps determine the concentration of the ALP enzyme in the blood. This allows doctors to evaluate liver function, investigate bone disorders, and monitor tumor diseases. So, what conditions is this test indicated for?
1. What is ALP?
Alkaline phosphatase (ALP or alkaline phosphatase) is an enzyme found in the liver, bones, placenta, small intestine, and kidneys, but primarily in the cells lining the bile ducts and in osteoblasts involved in the formation of new bone. ALP represents a family of enzymes that catalyze the hydrolysis of phosphate esters in an alkaline environment.
ALP has several different forms. Each form has a different chemical structure, known as an isoenzyme. The structure of isoenzymes depends on the organs in which they are produced, such as the liver and bone isoenzymes of ALP. In healthy individuals, more than 95% of the total serum ALP reflects the synthesis of bone isoenzymes (indicating osteoblast activity) and liver isoenzymes (alkaline phosphatase normally secreted from the liver into bile).
There is almost no biliary origin. Intestinal origin (not indicating a pathological condition) is sometimes found in people with blood type O and A. Fetal origin is seen towards the end of pregnancy (the last three months), and tumor origin is detected in liver, pancreatic, lung tumors, and even in healthy individuals.
2. ALP Testing
- For the liver, the ALP activity test is part of a basic liver function test. When the liver is damaged or has any disorders related to it, with symptoms such as jaundice, yellowing of the eyes, abdominal pain, nausea, and vomiting, the ALP test plays a crucial role in diagnosing the disease. The result of the ALP activity measurement is necessary information for doctors to diagnose conditions such as hepatitis, cirrhosis, cholecystitis, and bile duct obstruction.
- For bones, the ALP test is particularly useful for detecting conditions related to alkaline phosphatase levels in children, such as rickets, osteomalacia, and Paget’s disease. Additionally, the alkaline phosphatase levels in the blood have significant implications in assessing vitamin D deficiency, the presence of tumors, or abnormalities in bone development.
3. When should ALP testing be conducted?
- Jaundice;
- Abdominal pain;
- Vomiting;
- Rickets;
- Osteomalacia;
- Paget’s disease;
- Vitamin D deficiency;
- Bone tumors;
- Abnormal bone development;
- Tumor pathology: breast, lung, prostate, stomach, colon, kidney cancers, multiple myeloma.
4. Clinical significance of result values
4.1 Elevated ALP levels
4.2 Decreased ALP Levels
- Men: 30 – 100 U/L
- Women: 45 – 115 U/L
4.3 Factors Affecting Blood ALP Results
- Hemolyzed samples can falsely increase ALP test results;
- Blood samples taken from patients after eating can increase ALP activity by an additional 30 U/L;
- ALP activity is more than 25% higher in individuals with a high body mass index (BMI), increases by 10% in smokers, and decreases by 20% in female patients using oral contraceptives;
- Certain medications can raise blood ALP levels, such as: Angiotensin-converting enzyme inhibitors, Paracetamol, antibiotics, antipsychotic medications, non-steroidal anti-inflammatory drugs, thiazide diuretics, salicylates;
- Medications that can decrease ALP activity include: Combined oral contraceptives (Estrogen and progesterone), oxalate, propranolol, clofibrate.
