Makindo Medical Notes

Related Subjects: |Ferritin |CEA |ESR |CRP |ALP |LDH |HbA1c |Alpha Fetoprotein |Anti-Hu ab |Biochemical Lab values

🧪 Alpha-Fetoprotein (AFP) is a tumour marker most often used alongside β-hCG to monitor Non-Seminomatous Germ Cell Tumours (NSGCT). It is also clinically important in hepatocellular carcinoma (HCC) and pregnancy-related conditions.

📖 About

• Tumour marker with a relatively high incidence of false positives and false negatives.
• Best used for monitoring disease course and treatment response once a diagnosis is confirmed, rather than as a screening test.
• Serum AFP often rises prior to treatment and declines with effective therapy, making it a useful dynamic marker.

🧬 AFP as a Marker

• 🎯 NSGCT of the Testis (raised in ~50–70%).
• 🎯 NSGCT at other sites (40–60% of cases, rarely stage I).
• 🎯 Ovarian NSGCT.
• 🩸 Hepatocellular Carcinoma (HCC) – elevated in 70–90% (threshold >500 ng/mL strongly suggestive).
• 🧒 Hepatoblastoma – mainly in children, rare in adults.

🧾 Sample Requirements

• ⚠️ Avoid interference: if on high-dose biotin therapy (>5 mg/day), collect sample ≥8 hours after last dose.
• Adults: blood sample in a 5 mL gold-top gel tube (or rust-top in the Acute Unit).

👶 Normal Physiology

• In pregnancy, AFP is produced by the yolk sac, fetal GI tract, and liver.
• Passes via the placenta into maternal circulation → basis of maternal serum AFP testing.
• Structurally related to albumin; encoded by a gene on chromosome 4 (q arm).

📈 Causes of High AFP

• Adults:
  • Hepatocellular carcinoma (AFP >500 ng/mL is highly specific, though 10% remain normal).
  • Other liver pathology: acute viral hepatitis, alcoholic hepatitis, drug-induced hepatitis.
  • Used in combination with liver ultrasound for hepatoma screening.
• Children: Ataxia–telangiectasia.
• Pregnancy: Neural tube defects, multiple pregnancy, abdominal wall defects, fetal growth restriction, eclampsia, fetal loss.

📉 Causes of Low AFP

• Down’s Syndrome: Reduced maternal serum AFP is part of the triple/quadruple test in prenatal screening.
• NSGCT: In testicular nonseminoma, falling AFP suggests treatment response, while rising AFP indicates relapse.

🌟 Clinical Pearls

• AFP is not a screening tool due to limited sensitivity and specificity.
• Its greatest utility is in trend monitoring (rise or fall over time).
• Interpret AFP in context with β-hCG, LDH, imaging, and clinical findings.