Alpha-fetoprotein microheterogeneity: a potential biochemical marker for Down's syndrome

Our purpose was to examine the utility of analyzing alpha-fetoprotein (AFP) microheterogeneity assessed by lectin affinity in Down's syndrome (DS) screening. Maternal sera and amniotic fluids were collected from 18 women who were carrying DS fetuses and 70 unaffected pregnancies around 16 weeks of gestation. The percentages of AFP which reacted with Lens culinaris agglutinin (AFP-L2,3) were determined by lectin affinity electrophoresis. AFP-L2,3 levels were significantly increased (P<0.0001) in both maternal serum and amniotic fluid from DS-affected versus unaffected pregnancies. The fractional areas under the receiver operating characteristic curves were 0.835 and 0.700 (P=0.106) for AFP-L3 and AFP MoM (multiples of the median) in maternal serum. No correlation was found between AFP-L3 and AFP MoM in maternal serum (r=0.006). Our data suggest that the measurement of AFP-L3 in maternal serum is a potential biochemical marker for DS.