Kennerknecht I, Barbi G, Wolf M, Djalali M, Grab D, Terinde R, Vogel W
Abteilung Klinische Genetik der Universität, Ulm, Germany.
Prenat Diagn. 1993 Oct;13(10):929-44. doi: 10.1002/pd.1970131007.
An increasing number of cytogenetic prenatal diagnoses are performed on chorionic villus samplings. The accuracy of this method is influenced by chromosomal mosaicism, mostly confined to direct preparation methods. Especially those investigators who have experienced false-negative and false-positive findings propagate the combined use of direct and culture methods. Yet large collaborative studies have shown that in approximately two-thirds of diagnostic cases only one procedure is applied. Moreover, the accuracy of a cytogenetic investigation depends not only on the ontogenetic origin of the tissues investigated, but also on interacting factors such as the 'a priori risk' and the 'predictive value of a cytogenetic finding'. On this basis a differentiated prenatal diagnostic procedure is discussed, including either sole short-term culture (STC), combined STC and long-term culture (LTC), primary amniocentesis (AC), or primary percutaneous umbilical blood sampling (PUBS). The predictive value of the cytogenetic diagnosis from CVS varies significantly dependent on the a priori risk of a chromosome aberration and, in the case of an abnormal karyotype, on the specific chromosome involved. A non-mosaic and 'non-lethal' trisomy detected in STC is highly representative of the embryo/fetus, but there are exceptions of limited predictive value, e.g., trisomy 18. Guided by the strategy of an optional follow-up by LTC, AC, or PUBS in 1317 successive CV samplings, we are not aware of a false-negative diagnosis, but probably had one false-positive diagnosis: 47,XXY after STC; 46,XY after LTC. When referring to the rate of fetuses with an unbalanced karyotype expected in the different indication groups, a relative increase of false-positive findings in the very-low-risk group (maternal age < or = 35 years of age) and of false-negative findings in the very-high-risk group (abnormal ultrasonographic findings) of pregnant women when only performing CVS becomes obvious. Because of this dilemma, AC or--especially in the latter group--PUBS might be primarily offered to these indication groups instead of CVS.
越来越多的细胞遗传学产前诊断是通过绒毛取样进行的。这种方法的准确性受到染色体嵌合体的影响，主要局限于直接制片方法。尤其是那些经历过假阴性和假阳性结果的研究人员主张联合使用直接制片法和培养法。然而，大型合作研究表明，在大约三分之二的诊断病例中，只采用了一种方法。此外，细胞遗传学研究的准确性不仅取决于所研究组织的个体发生起源，还取决于相互作用的因素，如“先验风险 ”和 “细胞遗传学发现的预测价值”。在此基础上，讨论了一种差异化的产前诊断程序，包括单独的短期培养（STC）、联合STC和长期培养（LTC）、初次羊膜穿刺术（AC）或初次经皮脐血取样（PUBS）。绒毛取样的细胞遗传学诊断的预测价值因染色体畸变的先验风险以及在核型异常的情况下所涉及的特定染色体而异。在STC中检测到的非嵌合型和 “非致死性” 三体高度代表胚胎/胎儿，但也有预测价值有限的例外情况，例如18三体。在1317次连续绒毛取样中，以LTC、AC或PUBS进行选择性随访的策略为指导，我们没有发现假阴性诊断，但可能有一例假阳性诊断：STC后为47,XXY；LTC后为46,XY。当参考不同指征组中预期的核型不平衡胎儿的比例时，仅进行绒毛取样时，孕妇极低风险组（母亲年龄≤35岁）中假阳性结果的相对增加以及极高风险组（超声检查结果异常）中假阴性结果的相对增加就变得明显了。由于这种困境，对于这些指征组，可能首先提供AC或 —— 特别是在后一组中 —— PUBS，而不是绒毛取样。
