Lens culinaris agglutinin-reactive alpha-fetoprotein, an alternative variant to alpha-fetoprotein in prenatal screening for Down's syndrome.
BACKGROUND
Three serum tests, alpha-fetoprotein (AFP), human chorionic gonadotrophin and unconjugated oestriol, are now widely used for screening for Down's syndrome. Lens culinaris agglutinin-reactive alpha-fetoprotein (AFP-L3) is a variant of alpha-fetoprotein with alpha1-->6 fucose appended to the reducing terminal N-acetylglucosamine. It is the most prominent AFP detected in the serum of patients with hepatocellular carcinoma.


METHODS
We investigated microheterogeneities of the carbohydrate chain on AFP in fetal liver tissues, amniotic fluids and maternal sera obtained from pregnancies with Down's syndrome using lectin affinity electrophoresis with four lectins. The percentages of AFP-L3 in maternal sera from 22 Down's syndrome and 227 unaffected pregnancies were determined.


RESULTS
Unlike the case with AFP concentration, the percentage of AFP-L3 in maternal serum and amniotic fluid was similar, and apparently not influenced by membrane permeability. Knowing the percentage of AFP-L3 in maternal serum was effective for discriminating between Down's syndrome-affected pregnancies and unaffected pregnancies. The percentage of AFP-L3 in maternal serum identified 55% of Down's syndrome cases with a 5% false-positive rate.


CONCLUSIONS
AFP-L3 should be an effective replacement for AFP in prenatal Down's syndrome screening.
Yamamoto
R
R
Department of Obstetrics and Gynecology, Hokkaido University School of Medicine, Sapporo 060-8638, Japan. rityam@med.hokudai.ac.jp
Azuma
M
M
Hoshi
N
N
Kishida
T
T
Satomura
S
S
Fujimoto
S
S
D000328:Adult; D000653:Amniotic Fluid / Q000737:chemistry; D004314:Down Syndrome / Q000175:diagnosis*; D004586:Electrophoresis / Q000379:methods; D005260:Female; D005865:Gestational Age; D006801:Humans; D037102:Lectins; D008099:Liver / Q000737:chemistry / Q000196:embryology; D037121:Plant Lectins; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D020033:Protein Isoforms / Q000032:analysis / Q000737:chemistry; D012372:ROC Curve; D000509:alpha-Fetoproteins / Q000032:analysis* / Q000737:chemistry
D037102:Lectins; D037121:Plant Lectins; D020033:Protein Isoforms; D000509:alpha-Fetoproteins; C033619:lentil lectin