Davis's Lab & Diagnostic Tests

Alkaline Phosphatase and Isoenzymes

General

Synonym/Acronym:
Alk Phos, ALP and fractionation, heat-stabile ALP.

Common Use:
To assist in the diagnosis of liver cancer and cirrhosis, or bone cancer and bone fracture.

Specimen:
Serum (1 mL) collected in a red- or tiger-top tube. Plasma (1 mL) collected in a green-top (heparin) tube is also acceptable.

Normal Findings:
(Method: Spectrophotometry for total alkaline phosphatase, inhibition/electrophoresis for fractionation)

Total ALPConventional & SI UnitsBone FractionLiver Fraction
0–30 d
 Male75–375 units/L
 Female65–350 units/L
1–11 mo
 Male70–350 units/L
 Female80–330 units/L
1–5 yr
 Male56–350 units/L39–308 units/LLess than 8–101 units/L
 Female73–378 units/L56–300 units/LLess than 8–53 units/L
6–7 yr
 Male70–364 units/L50–319 units/LLess than 8–76 units/L
 Female73–378 units/L56–300 units/LLess than 8–53 units/L
8 yr
 Male70–364 units/L50–258 units/LLess than 8–62 units/L
 Female98–448 units/L78–353 units/LLess than 8–62 units/L
9–12 yr
 Male112–476 units/L78–339 units/LLess than 8–81 units/L
 Female98–448 units/L78–353 units/LLess than 8–62 units/L
13 yr
 Male112–476 units/L78–389 units/LLess than 8–48 units/L
 Female56–350 units/L28–252 units/LLess than 8–50 units/L
14 yr
 Male112–476 units/L78–389 units/LLess than 8–48 units/L
 Female56–266 units/L31–190 units/LLess than 8–48 units/L
15 yr
 Male70–378 units/L48–311 units/LLess than 8–39 units/L
 Female42–168 units/L20–115 units/LLess than 8–53 units/L
16 yr
 Male70–378 units/L48–311 units/LLess than 8–39 units/L
 Female28–126 units/L14–87 units/LLess than 8–50 units/L
17 yr
 Male56–238 units/L34–190 units/LLess than 8–39 units/L
 Female28–126 units/L17–84 units/LLess than 8–53 units/L
18 yr
 Male56–182 units/L34–146 units/LLess than 8–39 units/L
 Female28–126 units/L17–84 units/LLess than 8–53 units/L
19 yr
 Male42–154 units/L25–123 units/LLess than 8–39 units/L
 Female28–126 units/L17–84 units/LLess than 8–53 units/L
20 yr
 Male45–138 units/L25–73 units/LLess than 8–48 units/L
 Female33–118 units/L17–56 units/LLess than 8–50 units/L
21 yr and older
 Male35–142 units/L11–73 units/L0–93 units/L
 Female25–125 units/L11–73 units/L0–93 units/L
Values may be slightly elevated in older adults.

Description

Alkaline phosphatase (ALP) is an enzyme found in the liver; in Kupffer cells lining the biliary tract; and in bones, intestines, and placenta. Additional sources of ALP include the proximal tubules of the kidneys, pulmonary alveolar cells, germ cells, vascular bed, lactating mammary glands, and granulocytes of circulating blood. ALP is referred to as alkaline because it functions optimally at a pH of 9.0. This test is most useful for determining the presence of liver or bone disease.

Isoelectric focusing methods can identify 12 isoenzymes of ALP. Certain cancers produce small amounts of distinctive Regan and Nagao ALP isoenzymes. Elevations in three main ALP isoenzymes, however, are of clinical significance: ALP1 of liver origin, ALP2 of bone origin, and ALP3 of intestinal origin (normal elevations are present in Lewis antibody positive individuals with blood types O and B). ALP levels vary by age and gender. Values in children are higher than in adults because of the level of bone growth and development. An immunoassay method is available for measuring bone-specific ALP as an indicator of increased bone turnover and estrogen deficiency in postmenopausal women.

Indications

  • Evaluate signs and symptoms of various disorders associated with elevated ALP levels, such as biliary obstruction, hepatobiliary disease, and bone disease, including malignant processes
  • Differentiate obstructive hepatobiliary tract disorders from hepatocellular disease; greater elevations of ALP are seen in the former
  • Determine effects of renal disease on bone metabolism
  • Determine bone growth or destruction in children with abnormal growth patterns

Potential Diagnosis

Increased In:

Related to release of alkaline phosphatase from damaged bone, biliary tract, and liver cells

  • Liver disease:
    • Biliary atresia
    • Biliary obstruction (acute cholecystitis, cholelithiasis, intrahepatic cholestasis of pregnancy, primary biliary cirrhosis)
    • Cancer
    • Chronic active hepatitis
    • Cirrhosis
    • Diabetes (diabetic hepatic lipidosis)
    • Extrahepatic duct obstruction
    • Granulomatous or infiltrative liver diseases (sarcoidosis, amyloidosis, TB)
    • Infectious mononucleosis
    • Intrahepatic biliary hypoplasia
    • Toxic hepatitis
    • Viral hepatitis
  • Bone disease:
    • Healing fractures
    • Metabolic bone diseases (rickets, osteomalacia)
    • Metastatic tumors in bone
    • Osteogenic sarcoma
    • Osteoporosis
    • Paget’s disease (osteitis deformans)
  • Other conditions:
    • Advanced pregnancy (related to additional sources: placental tissue and new fetal bone growth; marked decline is seen with placental insufficiency and imminent fetal demise)
    • Cancer of the breast, colon, gallbladder, lung, or pancreas
    • Congestive heart failure
    • Familial hyperphosphatemia
    • Hyperparathyroidism
    • Perforated bowel
    • Pneumonia
    • Pulmonary and myocardial infarctions
    • Pulmonary embolism
    • Ulcerative colitis

Decreased In:

  • Anemia (severe)
  • Celiac disease
  • Folic acid deficiency
  • HIV-1 infection
  • Hypervitaminosis D
  • Hypophosphatasia (related to insufficient phosphorus source for ALP production; congenital and rare)
  • Hypothyroidism (characteristic in infantile and juvenile cases)
  • Nutritional deficiency of zinc or magnesium
  • Pernicious anemia
  • Scurvy (related to vitamin C deficiency)
  • Whipple’s disease
  • Zollinger-Ellison syndrome

Critical Findings

N/A

Interfering Factors

  • Drugs that may increase ALP levels by causing cholestasis include anabolic steroids, erythromycin, ethionamide, gold salts, imipramine, interleukin-2, isocarboxazid, nitrofurans, oral contraceptives, phenothiazines, sulfonamides, and tolbutamide.
  • Drugs that may increase ALP levels by causing hepatocellular damage include acetaminophen (toxic), amiodarone, anticonvulsants, arsenicals, asparaginase, bromocriptine, captopril, cephalosporins, chloramphenicol, enflurane, ethionamide, foscarnet, gentamicin, indomethacin, lincomycin, methyldopa, naproxen, nitrofurans, probenecid, procainamide, progesterone, ranitidine, tobramycin, tolcapone, and verapamil.
  • Drugs that may cause an overall decrease in ALP levels include alendronate, azathioprine, calcitriol, clofibrate, estrogens with estrogen replacement therapy, and ursodiol.
  • Hemolyzed specimens may cause falsely elevated results.
  • Elevations of ALP may occur if the patient is nonfasting, usually 2 to 4 hr after a fatty meal, and especially if the patient is a Lewis-positive secretor of blood group B or O.

Nursing Implications Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist with determining the presence of liver or bone disease.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s hepatobiliary and musculoskeletal systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • There are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • If the patient has a history of allergic reaction to latex, avoid the use of equipment containing latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding and hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post Test

  • A report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Nutritional Considerations: Increased ALP levels may be associated with liver disease. Dietary recommendations may be indicated and vary depending on the severity of the condition. A low-protein diet may be in order if the patient’s liver has lost the ability to process the end products of protein metabolism. A diet of soft foods may be required if esophageal varices have developed. Ammonia levels may be used to determine whether protein should be added to or reduced from the diet. Patients should be encouraged to eat simple carbohydrates and emulsified fats (as in homogenized milk or eggs) rather than complex carbohydrates (e.g., starch, fiber, and glycogen [animal carbohydrates]) and complex fats, which require additional bile to emulsify them so that they can be used. The cirrhotic patient should be carefully observed for the development of ascites, in which case fluid and electrolyte balance requires strict attention.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

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