Clinical evaluation of a single antibody RIA assay for alpha-fetoprotein.

Open neural tube defects have been associated with elevated levels of alpha-fetoprotein in maternal serum and amniotic fluid. In the present study, specimens were collected during 14 to 20 weeks of gestation in five laboratories. Dates were confirmed by ultrasound. Among 1,049 subjects included in total serum alpha-fetoprotein determinations, 25 infants were born with neural tube defects, one patient had intrauterine fetal demise, and 1,023 delivered normal infants. The false-negative rate for serum alpha-fetoprotein was 0.38%, and the false-positive rate was 0.29%. For the total 1,211 amniotic fluid specimens, 23 infants were born with neural tube defects. The false-negative rate for amniotic fluid alpha-fetoprotein was 0.25%. All were closed lesions. There were no false-positive values. This study reaffirms the value of screening for neural tube defects by means of serum alpha-fetoprotein RIA. It also negates the argument that serum screening would promote excessive amniocentesis.