Original Article Simultaneous identification of chromosomes 18, X and Y in uncultured amniocytes by using multi-primed in situ labelling technique Gadji M, Krabchi K, Drouin R. Simultaneous identification of chromosomes 18, X and Y in uncultured amniocytes by using multi- primed in situ labelling technique. Clin Genet 2005: 68: 15–22. # Blackwell Munksgaard, 2005 The aim of this study is to validate the multi-PRINS (primed in situ labelling) technique for simultaneous detection of chromosomes 18, X and Y in uncultured amniocytes for prenatal diagnosis of aneuploidy. The sites of the newly synthesized DNA sequences were showed as fluorescent signals by using immunochemistry. A multi-PRINS techni- que was specifically performed for simultaneous detection in the same cells of three chromosome targets, e.g. chromosomes 18, X and Y. Fluorescent signals corresponding to chromosomes 18, X and Y were showed as yellow, red and green colour spots, respectively. A multi- FISH technique using chromosome 18, X and Y probes was performed for comparison. Sixty cases were analysed using both multi-PRINS and multi-FISH. Fifty to two hundred nuclei were scored for each case for each technique. In all cases, there was no significant difference in the detection of chromosomes 18, X and Y regarding the sensitivity, the specificity and the efficiency; multi-PRINS and multi-FISH yield a similar distribution of the number of spots per nucleus. Both techniques were able to identify aneuploid cases without any ambiguity. Both multi-PRINS and multi-FISH can accurately and reliably detect aneu- ploidies involving chromosomes 18, X and Y in uncultured amniocytes. Finally, multi-PRINS represents a faster and more cost-effective alter- native to FISH for prenatal testing of aneuploidy in uncultured amniocytes. M Gadji, K Krabchi and R Drouin Service of Genetics, Department of Paediatrics, Faculty of Medicine and Health Sciences, Universite ´ de Sherbrooke, Sherbrooke, Quebec, Canada Key words: chromosomes 18, X and Y – FISH – prenatal diagnosis – PRINS Corresponding author: Re ´ gen Drouin, Service of Genetics, Department of Paediatrics, Faculty of Medicine, Universite ´ de Sherbrooke, 3001 12th Avenue North, Sherbrooke, Quebec, Canada J1H 5N4. Tel.: þ1 819 820 6827; fax: þ1 819 564 5217; e-mail: regen.drouin@usherbrooke.ca Received 19 December 2004, revised and accepted for publication 14 March 2005 Aneuploidy is the most frequent chromosomal abnormality reported in prenatal diagnosis. The majority of aneuploidies involve chromosomes 13, 18, 21, X and Y, and represent 95% of all chromosome abnormalities present in livebirths (1). The routine test for chromosome identifica- tion in prenatal diagnosis remains standard kar- yotyping using in vitro culture of cells collected during either amniocentesis or chorionic villus sampling. This technique allows the identifica- tion, characterization and diagnosis of a variety of numerical and structural chromosomal aberra- tions. Although it is accurate and reliable, it remains labour-intensive and time-consuming. Because several days of cell culture are required before analysis, results are usually not available before 1–2 weeks. Thus, there is a real need for a rapid method to detect common aneuploidies at prenatal diagnosis. FISH-based analysis of inter- phase nuclei with chromosome-specific probes allows fast analysis of chromosome copy number and structural chromosome abnormalities (2–4). However, the commercially available FISH probes for prenatal diagnosis are too expensive and then, not accessible in all cytogenetic labora- tories. Furthermore, the generation of locus-spe- cific probes is laborious and time-consuming. The PRINS technique provides an alternative approach for direct detection of human chromo- somes. It involves annealing of oligonucleotide primers specific to the individual chromosome targets, followed by in situ elongation using Taq Clin Genet 2005: 68: 15–22 Copyright # Blackwell Munksgaard 2005 Printed in Singapore. All rights reserved CLINICAL GENETICS doi: 10.1111/j.1399-0004.2005.00454.x 15