Cyclical variations in mood in normal women taking oral contraceptives.

non-binding fraction and the composition of amniotic fluid altered accordingly. This is apparently so. Since affinity chromatography is more complicated than conventional AFP assay it will probably be used on selected samples. If the method proves as reliable as suggested here, an appropriate strategy would be to lower the cut-off value to three standard deviations above the mean total AFP concentration and subject all samples with concentrations above this value to con-A-binding studies. Theoretically, this would give a high incidence of detection of open spina bifida with a specificity of nearly 100%.