(Potential) false-negative diagnoses in chorionic villi and a review of the literature

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Abstract
Objectives To assess the incidence of (potential) false‐negative findings of cytogenetic diagnosis in STC‐villi and/or LTC‐villi and to determine the best strategy for karyotyping chorionic villi in order to avoid false‐negative results. Methods 2476 chorionic villus samples were received for prenatal cytogenetic investigations. Karyotyping was routinely performed on STC‐ and LTC‐villi preparations by G‐banding. Fluorescence in situ hybridization (FISH) analyses were performed in addition to standard chromosome analysis when necessary. Sometimes follow‐up investigations like amniocentesis were performed before a definite prenatal cytogenetic result could be reported. Results In 2389/2476 (96.5%) of the cases, both STC‐ and LTC‐villi were investigated. Normal STC‐ with abnormal LTC‐villi results and finally an abnormal fetal karyotype were detected in ten cases (10/2389; 0.42%); in 9/10 of the cases the indication was fetal ultrasound abnormalities. Normal STC‐ and LTC‐villi and finally an abnormal fetal karyotype were detected in two cases (2/2389; 0.08%). Conclusion The most reliable technique for prenatal diagnosis after chorionic villus sampling (CVS) is the combination of the analysis of both STC‐ and LTC‐villi to reduce the incidence of false‐negative findings to a minimum. In the case of fetal ultrasound abnormalities with a small amount of villi available, the investigation of LTC‐villi is recommended over that of STC‐villi. Copyright © 2006 John Wiley & Sons, Ltd.