Alpha-fetoprotein Profile Four (AFP4), Pregnancy

Prenatal Screening Laboratory

Immunoassays

Alpha-fetoprotein

Unconjugated estriol

Human chorionic gonadotrophin

Dimeric Inhibin A

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Specimen Required:

Serum: 4 mL

Refer to Special Handling Requirements

Days Test Set Up:

Monday - Friday

Analytic Time:

48 hours

Reference Values:

Screen Negative for open fetal defects is defined as < 2.0 multiple of median (MoM) for AFP.

Screen Negative for Down syndrome is defined as < 1:150 modified risk, based on four analyte levels and maternal age.

Screen Negative for trisomy 18 is defined as <1:100 modified risk, based on three analyte levels and maternal age, applies to 15 - 22 weeks gestation.

CPT Code(s):

82105, 82677, 84702, 86336

Relevance:

The levels of these four analytes are related to risk for open fetal defects such as spina bifida, anencephaly, gastroschisis, and omphalocele as well as to risk for Down syndrome (trisomy 21) and trisomy 18.

Notes:

All abnormal results are telephoned to the referring physician's office or laboratory.

Reference(s)

• Haddow JE, Palomaki GE, Knight GJ, Williams J, Pulkkinen AJ, Canick JA, Saller DN, Bowers GB: Prenatal screening for Down's syndrome with use of maternal serum markers. N Engl J Med, 327:588-593, 1992.
• Haddow JE, Palomaki GE, Knight GJ, Foster DL, Neveux LM: Second trimester screening for Down's syndrome using maternal serum dimeric inhibin A. J Med Screen, 5:115-119, 1998.