Quick answer

AFP serves two roles: prenatal screening for neural-tube defects (elevated) and Down syndrome (low), plus adult liver-cancer surveillance in cirrhosis patients. Adult elevations demand imaging investigation — they rarely appear from benign causes.

Dual clinical contexts

Pregnancy: AFP produced by fetal liver/yolk sac — rises then falls through gestation. MSAFP (maternal serum) screening integrates with estriol/hCG/Inhibin A for quad-screen risk calculations. Elevated → neural-tube-defect workup; low → trisomy-21 association.

Adults: elevated AFP signals hepatocellular regeneration or malignancy. Cirrhosis patients get AFP+ultrasound every 6 months for early HCC detection (surveillance imperfect but standard).

Adult interpretation

<10 ng/mL: normal · 10–200: chronic hepatitis, cirrhosis, HCC possible, germ-cell tumors · 200–400+: strongly HCC-suggestive · >10,000: advanced HCC or nonseminomatous germ-cell tumors. LECTIN-reactive AFP fractionation distinguishes HCC from benign regeneration when totals ambiguous.

What AFP DOESN'T screen

AFP is NOT a general cancer screening test — ordering it as 'cancer blood work' in asymptomatic adults generates false-positive cascades. It serves established-disease monitoring (treatment response, recurrence) and high-risk-population surveillance only.

Non-malignant AFP elevations

Acute hepatitis flares (transient surge), cirrhosis (modest sustained elevations), tyrosinemia, ataxia-telangiectasia, and pregnancy (expected). Levels >500 essentially always pathologic — investigation mandatory.

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Frequently asked questions

My AFP is 15 — do I have liver cancer?

Normal-range with cirrhosis — surveillance continues; single mild elevation without ultrasound lesion is reassuring.

Can I test AFP during pregnancy without prenatal care?

Maternal AFP is standard prenatal screening — discuss with obstetric provider; interpreting without gestational-age context is unreliable.