The diagnostic performance of cytogenetic investigation in amniotic fluid cells and chorionic villi.

First-trimester chorionic villus sampling has not reached the popularity of second-trimester amniocentesis in prenatal cytogenetic diagnosis, in contrast to initial expectations. We investigated whether a difference in the diagnostic performances of cytogenetic investigation in amniotic fluid (AF) cells and chorionic villi in favour of AF-cells might justify this. Diagnostic performance was measured as laboratory failure rate, karyotype quality (G-band score, rate of follow-up samples, rate of wrong diagnoses), and karyotype representativity (rate of follow-up samples, rate of wrong diagnoses). From 1993-1999, 11 883 AF-samples were investigated (AF-cells). In chorionic villi, short term culture preparations solely were karyotyped from 1993-1996 (n=3499) (STC-villi), short and long-term culture preparations simultaneously provided a sufficient amount of tissue being available from 1997 onwards (n=1829) ((STC+LTC)-villi). Laboratory failure rates were the same after amniocentesis (0.40%) and chorionic villus sampling (0.50%). G-band scores (mean+/-SD) were equal in AF-cells (373+/-38.1) and LTC-villi (364+/-32.6) but significantly lower in STC-villi (311+/-34.6) (p=0.001). Follow-up sampling rates because of quality reasons were the same in AF-cells (0.14%), STC- villi (0.13%) and (STC+LTC)-villi (0.11%). Two wrong diagnoses turned up among AF-cells. Follow-up sampling rates because of representativity reasons differed significantly between AF-cells (0.10%), (STC+LTC)-villi (1.31%), and STC-villi (1.99%) (p<0.001). However, the ratios of the total numbers of follow-up samples and uncertain or abnormal cytogenetic results in STC, and (STC+LTC)-villi at cytogenetic risks > or =3% (0.132 and 0.160, respectively) were equal to that in AF-cells at risks <3% (0.155). Two wrong diagnoses were made in STC-villi. Diagnostic performance improved in the rank order of STC-villi, (STC+LTC)-villi and AF-cells. At cytogenetic risks > or =3%, (STC+LTC)-villi showed a diagnostic performance equal to that in AF-cells. This might justify a selective use of chorionic villus sampling.

Accuracy of abnormal karyotypes after the analysis of both short- and long-term culture of chorionic villi.

We report in detail the cytogenetic results of 1838 consecutive chorionic villus samples with the availability of both short-term culture (STC-villi) and long-term culture (LTC-villi) preparations in 1561 cases (84.9%). A high degree of laboratory success (99.5%) and diagnostic accuracy (99.8%) was observed; in four cases of low mosaicism, all four associated with the final birth of a normal child, a small risk of uncertainty was accepted. The combined analysis of STC- and LTC-villi reduced follow-up amniocenteses by one-third in comparison with the analysis of STC-villi alone. We believe that the desired level of quality and accuracy of prenatal cytogenetics in chorionic villi can only be achieved when both STC- and LTC-villi are available. We conclude that CVS might then be the mode of prenatal diagnosis of first choice in pregnancies with a high (cytogenetic) risk.