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Human α-fetoprotein (AFP) is a tumor-associated fetal mammalian glycoprotein involved in ontogenic and oncogenic growth.[1] This tumor marker is encoded by the AFP gene on chromosome 4q25.[2] The fetal protein is a 70-kDa single polypeptide chain containing 3% to 5% carbohydrate. This protein exhibits a triplicate domain structure configured by intramolecular loops dictated by disulfide bridging.[3] AFP occupies an α-1 anodic position in the electrophoretic profile, running slightly slower compared to albumin.[4] AFP is synthesized in the yolk sac, fetal liver, and gastrointestinal tract during pregnancy but is re-expressed in multiple adult tumors of mixed mesodermal or endodermal origin.[5] In the clinical laboratory, AFP has been employed both as a post-operational tumor marker and as a gestational age-dependent fetal defect marker, demonstrating utility in screening for neural tube defects and aneuploidies.[6] When a fetus has neural tube defects, maternal serum AFP levels are elevated, whereas chromosomal disorders are associated with lower levels.[7] Yolk sac and liver-derived AFP have different carbohydrate content. The half-life of AFP is 4 to 5 days. Similar to albumin, serum AFP binds and transports many ligands such as bilirubin, fatty acids, retinoids, steroids, heavy metals, dyes, flavonoids, phytoestrogens, dioxin, and various drugs.[8] AFP can be fractionated by affinity electrophoresis into 3 glycoforms: L1, L2, and L3, based on the reactivity with the lectin lens culinaris agglutinin.[9] AFP-L3 binds strongly to lens culinaris agglutinin through an additional α-1-6 fucose residue attached at the reducing terminus of N-acetylglucosamine, in contrast to the L1 isoform. The L1 isoform is typically associated with non-hepatocellular carcinoma inflammation of the liver disease.[10] The L3 isoform is specific to malignant tumors, and the detected presence can identify patients who need increased monitoring for the development of hepatocellular carcinoma in high-risk populations such as chronic hepatitis B and C and liver cirrhosis.[11]

Risks associated with phlebotomy include: Phlebitis Abnormal bruising and bleeding in patients with clotting disorders or those taking blood thinners Risks associated with amniocentesis include: Miscarriage Preterm delivery