Validation of fluorescence in situ hybridization (FISH) assay using an analyte-specific reagent in detecting aneuploidies of chromosomes 13, 18, 21, X, and Y in prenatal diagnosis

Abstract

Fluorescence In-Situ hybridization (FISH) is a sensitive and highly efficient technique commonly used in routine diagnostics. Most of these tests that use analyte-specific reagents are not approved by US Food and Drug Administration (FDA) but are developed by individual test laboratories. There is an emerging demand for prenatal diagnosis of aneuploidies by FISH. Since most of these assays are laboratory-developed tests, it is essential to validate them prior to their use in diagnosis. However, validation procedures of these assays are oversight despite the presence of several validation guidelines. To validate FISH assay using analyte-specific reagents in detecting aneuploidies of chromosomes 13, 18, 21, X, and Y as per American College of Medical Genetics (ACMG) guidelines in 2016. Analyte-specific reagents supplied by Oxford Gene Technologies were used in the validation process using blood and amniotic fluid samples obtained from healthy male and female adults and fetuses respectively. The validation process includes probe localization, evaluation of assay specificity, and establishment of lower cut-off and reportable reference ranges. Probe localization indicated a 100% specificity for all probes tested. Interphase FISH on uncultured amniotic fluid demonstrated significantly high (≥95%) overall disomic signal patterns for all autosomes and sex chromosomes tested. The reportable 95% confidence interval was 94.84, 94.84, 95.24, 94.54, and 94.54 for chromosomes 13, 18, 21, X, and Y respectively. The present study illustrates an experimental design in validating laboratory-developed FISH assay using analytespecific reagents in detecting aneuploidies of chromosomes 13, 18, 21, X, and Y as per ACMG guidelines. Test probes used in the present study are consistent with probe localization characteristics, assay specificity, and reportable reference ranges recommended by ACMG. Therefore, the FISH assay used in the present study could be recommended as a supplementary prenatal diagnostic test that can be carried out along with standard chromosomal analysis.