ABSTRACT
OBJECTIVE: Primed in situ labeling (PRINS) is an interesting alternative to the traditional fluorescence in situ hybridization (FISH) for the in situ detection of specific sequences in chromosome anomalies. It combines the sensitivity and specificity of the polymerase chain reaction with the specific in situ signal detection capability of FISH. METHODS: We performed PRINS on uncultured amniocytes and compared the results with standard cytogenetic analysis. In a prospective study, a total of 262 independent samples were analyzed for numerical aberrations of chromosome 18. RESULTS: In more than 95% of the cases PRINS reactions were successfully achieved. Neither false-positive nor false-negative results were obtained. 62 of the 262 cases were in parallel examined for chromosome 18 aneuploidies by FISH. Although there were significant differences in signal distribution, these did not lead to a different overall classification of the respective cases, i.e., the end results of disomic and trisomic cases for chromosome 18 were identical between FISH and PRINS. In 205 of 262 cases PRINS was performed for chromosomes X and Y. 97.6% of these samples were properly sex differentiated. CONCLUSIONS: The PRINS assay is a simple and cheap alternative to detect numerical aberrations of chromosome 18. However, the rate of false-positive results for chromosome X was calculated as 1% and the rate of false-negative ones for chromosome Y as 2%. Further investigations are required to transform PRINS into an alternative to conventional methods for routine rapid prenatal diagnosis of gonosomes.
