Molecular Detection of Trisomy 21 by Bicolor Competitive Fluorescent PCR

OBJECTIVE: To develop a reliable and specific method for rapid prenatal diagnosis of Trisomy 21 (Down syndrome). METHODS: We established a dual color competitive fluorescent Polymerase Chain Reaction (PCR) to measure the gene dosage of Down syndrome critical region (DSCR), a single copy sequence in chromosome 21. Another unique single copy sequence located on chromosome 2 (USC2) but not glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was chose as reference gene. RESULTS: The DSCR3/USC2 ratio of peripheral blood in trisomy 21 syndrome patients to normal subjects was 1.41∼1.74 to 0.93∼1.15, respectively (p < 0.01). Dual color competitive fluorescent PCR technique effectively differentiates the normal subjects from the Down syndrome patients. Next, according to the dual color competitive fluorescence quantitative PCR, among the 46 pregnant women, 3 cases were Down syndrome and 43 cases were normal, and these were confirmed by cytogenetic karyotype analysis. CONCLUSION: This indicated that the new technique may be a reliable and specific method for the rapid prenatal diagnosis of Trisomy 21.