Alkaline Phosphatase (T505) [Back]
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| RISK ASSESSMENT VALUE: |
This enzyme comes mainly from the bone and liver. The intestine and placenta also produce it. Elevations are usually related to rapid bone production/turnover or to liver disease, especially biliary tract disease. A concurrent elevation in GGT or 5' nucleotidase (especially without AST/ALT elevation) points toward the biliary tract or infiltrating disease as being the source. Concurrent transaminase elevations suggest hepatitis. Isolated elevations suggest bone as the source.
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| NORMAL RESULTS: |
30 - 115 U/L
Isolated elevations below 160 U/L may not carry much additional risk.
The normal range of serum alkaline phosphatase varies with the laboratory method used. Total alkaline phosphatase levels, when measured by chemical inhibition, range from 30 to 115 units/liter. Since alkaline phosphatase concentrations rise during active bone formation in growth, infants children and adolescents normally have levels that may be three times as high as those of adults. Pregnancy also causes a physiologic rise in alkaline phosphatase levels which returns to normal within one month of delivery.
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| ABNORMAL RESULTS: |
Isolated elevations not associated with a physiologic cause (see above) are most likely related to rapid bone turnover/repair. Paget's disease, bony metastasis, hyperparathyroidism and fractures are all potential causes.
Elevation in conjunction with GGT elevation with normal transaminases suggests biliary disease including stones and biliary cirrhosis or infiltrative disease such as sarcoid or tumor. Concurrent elevation of transaminases suggests some type of hepatitis.
Drugs including: allopurinol, tetracycline, anticonvulsants, hormonal Rx, antiarrythmics and some antibiotics may be associated with elevation.
Low alkaline phosphatase in isolation is not generally of concern.
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| ADDITIONAL TESTS: |
Isoenzymes may help determine source of elevation but are rarely done since if liver is the source, other enzymes such as GGT are typically elevated as well.
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| SAMPLE NEEDED: |
Separated serum from a red-stopper tube.
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| SAMPLE STABILITY: |
10 days at room temperature, 2 weeks when refrigerated, indefinitely when frozen
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| METHOD & INSTRUMENT: |
p-Nitrophenylphosphate is hydrolyzed to phosphate and p-nitrophenol, Hitachi Modular.
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| INTERFERING FACTORS: |
Hemolysis decreases serum alkaline phosphatase activity.
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| PURPOSE: |
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| PROFILE INCLUDES: |
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| RISK RANGE & UNITS: |
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