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ALPHA-FETOPROTEIN (AFP)

Item Value
Available Stat? No
Test code AFP
Performed by? Chemistry
Sendout? no
Price range $$$
In House Availability Monday - Friday
Saturday & Sunday, 12:00 pm - 8:00 pm
Principle The Siemens Centaur assay is a two-site immunoassay using direct Chemiluminometric technology
Interpretation AFP is elevated in hepatoma (70%), teratoblastoma and embryonal cell carcinoma of testes or ovary (90%), usually at concentrations > 400 mcg/L. Serial monitoring is useful in detecting post-op early recurrence or response to chemotherapy. AFP is a product also of several GI and lung tumors, appearing in concentrations of 10-400 ng/mL. Commonly, AFP is minimally elevated in cirrhosis, viral hepatitis (40%) and ataxia telangiectasia.
Container type gold gel tube
Amount to Collect 2.0 mL
Collection Instructions Plasma samples cannot be assayed.
Sample type Blood
Normal range 0-8.5 mcg/L
Synonyms AFP;
Stability Serum is stable 48 hours at 2-8°C; one month at -20°C
Interferences 1. Auto- (rheumatoid factor) and heterophile antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference. Anomalous values may be observed. The most common, although not exclusive, interference seen in immunometric ("two-site," or "sandwich") assays is a spuriously high value. Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).

2. A paradoxical, false low result may rarely occur when patient samples with extremely high concentrations of peptide/protein analytes (e.g. AFP, hCG, PSA, etc.) are measured by immunometric ("two-site," or "sandwich") assays. For example, a true value of 3,000,000 U/L could be reported as < 5 or 21 U/L. This phenomenon is called the "high dose hook effect." Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).

3. This assay is standardized against the W.H.O. Reference Preparation 72/225 using highly purified AFP.

4. The concentration of AFP in a given specimen, as determined by assays from different manufacturers, can vary due to differences in assay methods and reagent specificity. Values obtained with different AFP assays cannot be used interchangeably.
References 1. Bayer, Advia Centaur, 111778 Rev. 2002-04. Siemens Medical Solutions Diagnostics, Malvern, PA.

2. Henry, JB, ed: Clinical Diagnosis and Management by Laboratory Methods. ed. 20, Philadelphia: W.B. Saunders, 1037; 2001.

3. Tietz, N.W. Textbook of Clinical Chemistry and Molecular Diagnosis, ed. 4. St. Louis, MO: Elsevier Saunders, 767-769; 2006.
CPT coding 82105
Last Updated 10/17/2012 10:11:52 AM
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