Effectiveness of prenatal chromosomal analysis using multicolour fluorescent in situ hybridisation

Objective To evaluate the clinical effectiveness of multicolour fluorescent in situ hybridization (FISH) analysis in routine prenatal diagnosis, Design Prospective study. Sample 3203 amniotic fluid samples. Methods Unique DNA (chromosomes 13 and 21) and alpha satellite centromeric- specific (chromosomes X, Y and Is) probes were used in two mixes to permit the simultaneous analysis of several chromosomes. The performance of multic olour FISH and conventional cytogenetic analysis tvas compared. Results Conventional cytogenetic analysis identified III chromosomal abnorm alities, of which 94 were potentially detectable by the FISH technique and 97 would be typically associated with neonatal phenotypic abnormalities. Mu lticolour FISH analysis detected 84% (93/111) of all chromosome abnormaliti es and 99% (93/94) of abnormalities where there was a specific probe, The s ensitivity; of multicolour FISH analysis was 95% (92/97) for chromosomal ab normalities likely to result in an abnormal postnatal outcome. Multiple ult rasound abnormalities were detected in aa five: cases of clinically relevan t chromosomal abnormalities missed by muticolour FISH. FISH results were av ailable within 48 hours and the sample failure rate was 0.1% (3/3202). Conclusion Multicolour FISH analysis is a sensitive and reliable technique for the rapid prenatal diagnosis of chromosomal abnormalities. Examining on ly five chromosomes allowed 95% of clinically relevant chromosomal abnormal ities to be diagnosed correctly As routine antenatal screening is targeted at the major autosomal trisomies and sex chromosome aneuploidies, multi col our FISH analysis may potentially replace conventional cytogenetic analysis in routine prenatal diagnosis.