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Test Code LAB4008 ALKALINE PHOSPHATASE (ALP)

Important Note

Useful for:

  • Diagnosing and monitoring treatment of liver, bone, intestinal and parathyroid diseases

Additional Codes

Labcorp 001107

Specimen Type

Preferred Sample: Lithium Heparin Plasma (Light Green Top)
Alternate Sample:  Serum Tube (SST, Gold, Corvac, Tiger, Red Top Tube)

Specimen Volume

Preferred: 1.0 mL

Minimum: 0.5 mL

 

Sample Stability

Room Temp: 7 days
Refrigerated: 7 days

Frozen: 2 months

Clinical Information

Human alkaline phosphatase (ALP) consists of at least five tissue-specific isoenzymes which catalyze the hydrolysis of phosphate mono-esters at a pH that is alkaline. A variety of disease processes can result in the release of increased quantities of ALP into the bloodstream. Elevation in serum ALP is used as an aid to detect various hepatobiliary and bone diseases. In order to distinguish between liver or bone source, clinical findings and additional diagnostic tools such as liver function tests including gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are used. A biliary obstruction may present with ALP levels 10 to 12 times the upper reference limit and usually return to baseline on removal of the obstruction. ALP levels are usually elevated in hyperthyroidism and hyperparathyroidism. ALP is also a useful marker for the management of patients the Paget disease, osteomalacia, and osteoporosis. ALP expressed by intestinal epithelial cells and secreted into serum serves as a marker of intestinal diseases.

Limitations

  • Interferences from medication or endogenous substances may affect results.
    • Penicillin derivitives
    • Antiepileptics
    • Antihistamines
    • Cardiovascular drugs
    • Others
  • Day-to-day variation is 5-10%
  • recent food ingestion may increase levels as much as 30 U/L
  • ALP is 15% and 10% higher in African American men and women, respectively, compared to other racial/ethnic groups
  • 25% higher in patients with increased BMI, 10% with smoking and 20% lower with the use of oral contraceptives

Method

Enzymatic/Colormetric (Para-nitrophenyl phosphate)

 

Alkaline phosphatase in the sample catalyzes the hydrolysis of colorless p-nitrophenyl phosphate (p-NPP) to give p-nitrophenol and inorganic phosphate. At the pH of the assay (alkaline), the p nitrophenol is in the yellow phenoxide form. The rate of absorbance increase at 404 nm is directly proportional to the alkaline phosphatase activity in the sample. Optimized concentrations of zinc and magnesium ions are present to activate the alkaline phosphatase in the sample.

Reference Ranges

 

ALP, U/L
  Male Female
0-15 Days 90 - 273
15 Days - 1 Year 134 - 518
1-10 Years 156 - 369
10-13 Years 141 - 460
13-15 Years 127 - 517 62 - 280
15-17 Years 89 - 365 54 - 128
17-19 Years 59 - 164 48 - 95
>19 Years 40 - 150

Test Components

ALP: U/L

Measuring Range 9 - 4555 U/L

Reporting Limits 9 - 4555 U/L

Turnaround Time

STAT: 1 hour
Routine: 4 hours

Test Schedule

Daily and STAT

CPT Code

84075

LOINC Code

6768-6

IMO Code

IMO-PROC-30999576