A reappraisal of amniotic fluid alpha-fetoprotein measurement at the time of genetic amniocentesis and midtrimester ultrasonography.
OBJECTIVE
To evaluate the contemporary utility of amniotic fluid alpha-fetoprotein measurement as a complementary test for fetal abnormalities at the time of invasive genetic testing.


METHODS
A review of amniotic fluid alpha-fetoprotein test results was conducted to determine the frequency with which elevated alpha-fetoprotein values added independent diagnostic information and altered clinical management. Amniotic fluid specimens processed for alpha-fetoprotein between 1995 and 1998 were included. Elevated alpha-fetoprotein cases were classified as either incidental to the fetal abnormality diagnosed or central to the identification of a fetal anomaly on the basis of whether an ultrasonographic examination had already identified the anomaly before amniocentesis. The costs associated with alpha-fetoprotein testing were used to estimate the expenditure per pregnancy in which elevated alpha-fetoprotein values would add discriminatory diagnostic value. A hypothetical national cost model was constructed to explore the utility of selective rather than routine amniotic fluid alpha-fetoprotein measurement.


RESULTS
Eighty-two (3%) of 2769 amniotic fluid alpha-fetoprotein values were elevated. In only 1 instance was the elevated result found to be partially discriminatory (e.g., an established diagnosis of microcephaly with an associated small encephalocele identified after the elevated amniotic fluid alpha-fetoprotein value prompted repeated ultrasonographic assessment). Sixty-one other neural tube defects were detected by ultrasonography alone (myelomeningocele, n = 28; anencephaly, n = 24; and encephalocele, n = 9). Thus, an elevated alpha-fetoprotein result added diagnostic precision in only 1 (0.036%) of 2769 cases. Cost estimates suggested that routine amniotic fluid alpha-fetoprotein assessment resulted in a $219,000 expenditure per informative case.


CONCLUSIONS
Routine measurement of amniotic fluid alpha-fetoprotein during amniocentesis may not be warranted in centers with expertise in targeted ultrasonographic imaging.
Silver
R K
RK
Department of Obstetrics and Gynecology, Evanston Northwestern Healthcare, Northwestern University Medical School, Illinois, USA.
Leeth
E A
EA
Check
I J
IJ
D000293:Adolescent; D000328:Adult; D000649:Amniocentesis; D000653:Amniotic Fluid / Q000737:chemistry*; D003365:Costs and Cost Analysis; D005260:Female; D006801:Humans; D011247:Pregnancy; D016216:Ultrasonography, Prenatal / Q000191:economics; D000509:alpha-Fetoproteins / Q000032:analysis*
D000509:alpha-Fetoproteins