FastFISH: technique for ultrarapid fluorescence in situ hybridization on uncultured amniocytes yielding results within 2 h of amniocentesis.

Rapid aneuploidy detection methods allow prenatal diagnosis results to be released within 48 h, but not on the same day as the invasive test. We aimed to develop a rapid fluorescence in situ hybridization (FISH) method (FastFISH) that releases accurate results on the same day as amniocentesis. FastFISH was optimized to be completed within 2 h of sample collection using CEP and LSI probes for chromosomes 13, 18, 21, X, Y and DiGeorge syndrome (DGS). The technique was tested on 100 consecutive amniotic fluid samples in a blinded study. It was also validated as a 1-day molecular genetic test on three representative fetal tissue samples: chorionic villus, amniotic fluid and fetal blood. In the blinded study, FastFISH results were ready within 2 h of sample collection. Of the 100 amniotic fluid samples, 49 male and 50 female fetuses were identified. One fetus was 47, XXY (Klinefelter syndrome). Three fetuses had trisomy 21. One fetus suspected of DGS by ultrasound was identified as normal. Results of FastFISH analyses in all 100 cases were concordant with their karyotypes (100% accuracy; lower 95% CI, 97.05%). In the 1-day test validation, all results were released on the same day and were concordant with their respective karyotypes. FastFISH allows results to be released on the same day as amniocentesis. It represents the necessary development for a 1-day prenatal diagnosis service.