Differential staining techniques in amniotic fluid cytology diagnosis of neural tube defects: A prospective study of 129 pregnancies

Abstract

In order to assess the utility of amniotic fluid cytology in the diagnosis of neural tube defects (NTDs), we performed a prospective study of 129 pregnancies selected for maternal age or history of prior congenital defects or multiple stillbirths. Amniotic fluid obtained between the 16th and 22nd weeks of gestation was cytocentrifuged and stained with hematoxylineosin (H&E), Papanicolaou, and Diff-Quik. Chromosomal analysis, amniotic fluid alpha fetoprotein (AFP) level, and eventual pregnancy outcome were recorded for each case. The AFP levels were normal in 128 cases, including two closed NTDs (meningomyelocele and encephalocele). Three patients had abnormal chromosomal studies: two with 47,XXX and one with trisomy 21. Of these 128 cases, 16 had inadequate cytologic preparations; the remainder, including the five aforementioned patients, showed predominantly squamous cells, amnion cells, and minicells. Other cell types, including genito-urinary cells, umbilical cord cells, respiratory cells, and macrophages, were also present in smaller numbers. One case exhibited a large population of small, darkly staining neural cells and large macrophages. The AFP in this case was markedly elevated, and the fetus was noted to be anencephalic. We found the H&E to be the preferred stain for both cytologic detail and minicell preservation; however papanicolaou was better for bloody specimens. Amniotic fluid cytology may provide a rapid and inexpensive method of confirming the diagnosis of open NTDs.