title: Interpreting elevated amniotic fluid alpha-fetoprotein levels in clinical practice: use of the predictive value positive concept.
abstract: The amniotic fluid alpha-fetoprotein assay (AF-AFP) is the single most valuable method of detecting anencephaly--spina bifida (ASB) in utero. A raised AF-AFP, however, is a more reliable indicator of a fetus with ASB in the pregnancy at high risk for ASB. Most women undergoing fetal chromosomal analysis are at low risk for ASB. Consequently, gravid patients who have an AF-AFP incidental to chromosomal studies, and elect abortion because of a raised AF-AFP, will more frequently abort a normal fetus than the gravida who has previously had an infant with ASB. For the obstetrician utilizing this assay, the predictive value positive (PVP) concept, a guide for the interpretation of a positive result, is introduced and then applied to examples of patients at varying risk for ASB in their offspring.
mesh_terms: D000649:Amniocentesis; D000653:Amniotic Fluid / Q000032:analysis*; D000757:Anencephaly / Q000175:diagnosis* / Q000453:epidemiology; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008403:Mass Screening; D011247:Pregnancy; D012306:Risk; D016136:Spina Bifida Occulta / Q000175:diagnosis* / Q000453:epidemiology; D014463:Ultrasonography; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D000509:alpha-Fetoproteins