Alpha-fetoprotein (AFP) is a protein produced mainly by the liver and yolk sac of a developing fetus. Its levels are typically elevated in fetal development but decrease significantly after birth. In adults, AFP is present in very small amounts, and abnormal levels can indicate certain medical conditions.

Uses of the AFP Test

1. In Adults (Non-Pregnant):

• Tumor Marker:
• AFP is used to help diagnose and monitor cancers, particularly:
• Liver cancer (hepatocellular carcinoma).
• Germ cell tumors of the testicles or ovaries.
• Metastatic cancers (spreading to the liver).
• Monitoring Chronic Liver Conditions:
• Elevated AFP can be seen in chronic liver diseases like hepatitis or cirrhosis, which may increase the risk of cancer.

1. In Pregnancy:

• Screening for Fetal Abnormalities:
• AFP levels in maternal blood are measured to assess the risk of:
• Neural tube defects (e.g., spina bifida, anencephaly).
• Abdominal wall defects (e.g., gastroschisis, omphalocele).
• Chromosomal abnormalities (e.g., Down syndrome, Edwards syndrome).
• Part of the quad screen test conducted in the second trimester (16–18 weeks).

AFP Test Procedure

• For Adults:
• A blood sample is taken from a vein to measure AFP levels.
• For Pregnant Women:
• A blood sample is taken, and AFP is measured as part of maternal serum screening.

Normal AFP Levels

In Adults (Non-Pregnant):

• Normal Range: <10 ng/mL (varies slightly between laboratories).
• Elevated levels can indicate:
• Mild elevation (10–500 ng/mL): Liver regeneration (e.g., hepatitis or cirrhosis), germ cell tumors.
• High levels (>500 ng/mL): Strongly associated with liver cancer or metastatic disease.

In Pregnancy:

• Normal levels: Depend on gestational age, peaking around the second trimester.
• Abnormal results:
• High AFP: May indicate neural tube defects, multiple pregnancies, or abdominal wall defects.
• Low AFP: May suggest chromosomal abnormalities like Down syndrome or Edwards syndrome.

Conditions Associated with Abnormal AFP Levels

1. Elevated AFP in Adults:

• Primary liver cancer (hepatocellular carcinoma).
• Metastatic cancer involving the liver.
• Testicular or ovarian germ cell tumors.
• Chronic liver diseases like hepatitis or cirrhosis.

1. Low AFP in Pregnancy:

• Down syndrome (trisomy 21).
• Edwards syndrome (trisomy 18).

1. High AFP in Pregnancy:

• Neural tube defects like spina bifida.
• Abdominal wall defects.
• Miscalculated gestational age or multiple pregnancies.

Follow-Up Testing

Abnormal AFP levels usually require additional diagnostic tests, such as:

• Ultrasound or MRI: To locate tumors or confirm fetal abnormalities.
• Amniocentesis: To assess fetal chromosomal health.
• Liver biopsy: To confirm liver cancer.

Clinical Importance of AFP

• Cancer Diagnosis and Monitoring:
• AFP helps detect and monitor treatment responses for cancers, particularly liver and germ cell cancers.
• Fetal Health Screening:
• AFP is a critical component of prenatal care to detect potential fetal anomalies early.

Results should always be interpreted in the context of clinical findings and other diagnostic tests.