Alkaline Phosphatase, Serum

CPT CODE:

USEFUL FOR:

Diagnosis and treatment of liver, bone, intestinal, and parathyroiddiseases.

SPECIMEN REQUIRED:

Draw blood in a plain, red-top tube(s) or a serum gel tube(s). Spin down and send 0.5 mL of serum either refrigerated or frozen in plastic vial.Note:    Patient's age and sex are required on request form               for processing.

TRANSPORT TEMPERATURE:

Frozen\Refrig OK\Ambient NO

CLINICAL INFORMATION:

Alkaline phosphatase (ALP) is present in a number of tissues including liver, bone, intestine, and placenta. Serum ALP is of interest in the diagnosis of 2 main groups of conditions-hepatobiliary disease and bone disease associated with increased osteoblastic activity. 
A rise in ALP activity occurs with all forms of cholestasis, particularly with obstructive jaundice. The response of the liver to any form ofbiliary tree obstruction is to synthesize more ALP. The main siteof new enzyme synthesis is the hepatocytes adjacent to the biliarycanaliculi.
ALP also is elevated in disorders of the skeletal system that involve osteoblast hyperactivity and boneremodeling, such as Paget's disease, rickets and osteomalacia,fractures, and malignant tumors.
Moderate elevation of ALP may be seen in other disorders such as Hodgkin's disease, congestive heart failure, ulcerative colitis, regional enteritis, and intra-abdominal bacterial infections.

CLINICAL INTERPRETATION:

The elevation in ALP tends to be more marked (more than 3 fold)in extrahepatic biliary obstruction (e.g., by stone or by cancer ofthe head of the pancreas) than in intrahepatic obstruction, and isgreater the more complete the obstruction. Serum enzymeactivities may reach 10-12 times the upper limit of normal, returningto normal on surgical removal of the obstruction.
The ALP response to cholestatic liver disease is similar to theresponse of gamma-glutamyltransferase (GGT), but more blunted.If both GGT and ALP are elevated, a liver source of the ALP is likely.  Among bone diseases, the highest level of ALP activity is encountered in Paget's disease as a result of the action of the osteoblastic cells as they try to rebuild bone that is being resorbed by the uncontrolled activity of osteoclasts. Values from 10-25 times the upper limit of the reference interval is not unusual. Only moderate rises are observed in osteomalacia, while levels are generally normal in osteoporosis. In rickets, levels 2-4 times normal may be observed. Primary and secondary hyperparathyroidism are associated with slight to moderate elevations of ALP, the existence and degree of elevation reflects the presence and extent of skeletal involvement.  Very high enzyme levels are present in patients with osteogenic bone cancer. A considerable rise in ALP is seen in children followingaccelerated bone growth.
In addition, an increase of 2-3 times normal may be observed in women in the third trimester of pregnancy, although the interval is very wide and levels may not exceed the upper limit of the reference interval in some cases. The additional enzyme is of placental origin.

REFERENCE VALUES:

Males

      4 years: 149-369 U/L

      5 years: 179-416 U/L

      6 years: 179-417 U/L

      7 years: 172-405 U/L

      8 years: 169-401 U/L

      9 years: 175-411 U/L

      10 years: 191-435 U/L

      11 years: 185-507 U/L

      12 years: 185-562 U/L

      13 years: 182-587 U/L

      14 years: 166-571 U/L

      15 years: 138-511 U/L

      16 years: 102-417 U/L

      17 years: 69-311 U/L

      18 years: 52-222 U/L

      > or =19 years: 45-115 U/L

Females

      4 years: 169-372 U/L

      5 years: 162-355 U/L

      6 years: 169-370 U/L

      7 years: 183-402 U/L

      8 years: 199-440 U/L

      9 years: 212-468 U/L

      10 years: 215-476 U/L

      11 years: 178-526 U/L

      12 years: 133-485 U/L

      13 years: 120-449 U/L

      14 years: 153-362 U/L

      15 years: 75-274 U/L

      16 years: 61-264 U/L

      17-23 years: 52-144 U/L

      24-45 years: 37-98 U/L

      46-50 years: 39-100 U/L

      51-55 years: 41-108 U/L

      56-60 years: 46-118 U/L

      61-65 years: 50-130 U/L

      > or =66 years: 55-142 U/L