Segmental Duplications as a Complement Strategy to Short Tandem Repeats in the Prenatal Diagnosis of Down Syndrome

Background: quantitative fluorescence-polymerase chain reaction (qf-pcr) is an inexpensive and accurate method for the prenatal diagnosis of aneuploidies that applies short tandem repeats (strs) as a chromosome-specific marker. despite its apparent advantages, qf-pcr is not applicable in all cases due to the presence of uninformative strs. this study was carried out to investigate the efficiency of a method based on applying segmental duplications (sds) in conjunction with strs as an alternative to stand-alone str-based qf-pcr for the diagnosis of down syndrome. methods: fifty amniotic fluid samples from pregnant women carrying down syndrome fetuses, 9 amniotic fluid samples with 1 or without any informative str marker (inconclusive), and 100 normal samples were selected from shiraz, iran, between october 2015 and december 2016. analysis was done using an in-house str-sd-based multiplex qf-pcr and the results were compared. statistical analysis was performed using medcalc, version 14. results: all the normal, down syndrome, and inconclusive samples were accurately identified by the str-sd-based multiplex qf-pcr, yielding 100% sensitivity and 100% specificity. karyotype analysis confirmed all the cases with normal or trisomic results. conclusion: the str-sd-based multiplex qf-pcr correctly identified all the normal and trisomy 21 samples regardless of the absence of informative str markers. the str-sd-based multiplex qf-pcr is a feasible and particularly useful assay in populations with a high prevalence of homozygote str markers.