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Test Code LAB5008 ALPHA-FETOPROTEIN TUMOR MARKER (AFP)

Important Note

Useful for:

  • Follow-up management of patients undergoing cancer therapy, especially for testicular and ovarian tumors and for hepatocellular carcinoma
  • Marker for hepatocellular and germ cell (nonseminoma) carcinoma
  • Often used in conjunction with human chorionic gonadotropin.

This test is NOT useful for:

  • Screening for cancer in the general population
  • The detection of neural tube defects
  • Patients with pure seminoma or dysgerminoma

Specimen Type

Preferred Specimen: Lithium Heparin Plasma (Mint/Light Green Top Tube)

Alternate Specimen: Serum (SST, Gold, Corvac, Tiger, Red Top Tube), Lithium Heparin Plasma (Dark green top tube)

Specimen Volume

Preferred:1 mL

Minimum: 0.5 mL

Sample Stability

Room Temperature: 3 days

Refrigerated: 7 days

Clinical Information

Alpha-fetoprotein (AFP) is a single polypeptide chain glycoprotein with physicochemical properties similar to those of albumin. Synthesis of AFP occurs primarily in the liver and yolk sac of the fetus. It is secreted into fetal serum, reaching a peak at about 13 weeks gestation and gradually declining thereafter. Elevated serum AFP levels appear during pregnancy and in conjunction with several malignant diseases.

 

AFP testing in maternal serum during pregnancy is an effective way to determine those women potentially at risk of carrying a fetus affected with an open neural tube defect. Used in conjunction with other confirmatory procedures such as ultrasonography or amniography, measurement of AFP serves as an important tool in the care and management of these patients. AFP testing on maternal serum is not performed at Kootenai Health.

 

Elevated serum AFP values also occur in several malignant diseases, most notably nonseminomatous testicular cancer and primary hepatocellular carcinoma. In the case of nonseminomatous testicular cancer, a direct relationship has been observed between the incidence of elevated AFP levels and the stage of disease. Greater than 70% of patients with primary hepatocellular carcinoma have been reported to have elevated levels of serum AFP. Elevation of serum AFP in benign hepatic diseases is usually transient.

Limitations

  • AFP testing is not recommended as a screening procedure to detect cancer in the general population
  • The concentration of alpha-fetoprotein (AFP) in each specimen, determined with assays from different manufacturers, can vary due to differences in assay methods and reagent specificity. Values obtained with different assay methods cannot be used interchangeably. If, while monitoring a patient, the assay method used for determining AFP levels serially is changed, additional sequential testing should be carried out.
  • When serial specimens are being evaluated, the same type of specimen should be used throughout the study
  • Serum levels do not correlate well with other clinical features of hepatocellular carcinoma, such as size, stage or prognosis
  • False elevations can occur with tumors of the GI tract or with liver damage (e.g. hepatitis, cirrhosis, and drug or alcohol abuse) and pregnancy
  • Lysis of tumor cells during chemotherapy may transiently elevate levels

Method

Chemiluminescent microparticle immunoassay (CMIA)

 

This assay is a two-step immunoassay for the quantitative determination of AFP in human serum and plasma using chemiluminescent microparticle immunoassay (CMIA) technology.

 

Sample and anti-AFP coated paramagnetic microparticles are combined and incubated. The AFP present in the sample binds to the anti-AFP coated microparticles. The mixture is washed. Anti -AFP acridinium-labeled conjugate is added to create a reaction mixture and incubated. Following a wash cycle, Pre-Trigger and Trigger Solutions are added.

 

The resulting chemiluminescent reaction is measured as relative light units (RLUs). There is a direct relationship between the amount of AFP in the sample and the RLUs detected by the system optics.

Reference Ranges

<15.00 ng/mL

 

Measuring Range 2.00 – 2000.00 ng/mL

Reporting Limits 2.00 – 20,000.00 ng/mL

If result after a 1:10 dilution is greater than 20,000.00 ng/mL, report out >20,000.00 ng/mL.

Turnaround Time

STAT: 1 hour

Routine: 4 hours

Timed: 4 hours

Test Schedule

Daily

CPT Code

82105