RESUMEN
BACKGROUND: Quantitative-fluorescent polymerase chain reaction (QF-PCR) is a reliable, rapid, and economic technique for prenatal diagnosis of the most common abnormalities. However, conventional karyotyping is expensive and requires a much longer time to yield results. It is currently under debate whether the replacement or restriction of karyotyping reduces the quality of prenatal test results. This study was undertaken to determine the percentage of clinically significant chromosomal abnormalities that would not be detected if QF-PCR was the main analysis method and karyotyping reserved for cases with increased nuchal translucency (NT) and/or abnormal ultrasound findings and to estimate the difference in cost between QF-PCR and full karyotyping. METHODS: Nine hundred twenty-eight pregnant women underwent an invasive procedure at our center between May 2009 and December 2012, yielding 580 (62.5%) chorionic villous samples and 348 (37.5%) amniotic fluid samples. Samples were studied by both QF-PCR and full karyotyping. Karyotyping and detailed ultrasound findings were retrospectively analyzed. RESULTS: If QF-PCR was the main analytic method and full karyotyping reserved for cases with elevated NT (≥4.5) and/or abnormal ultrasound findings, 12.7% of the patients would have required full karyotyping, 99% of the clinically significant chromosomal abnormalities would have been detected, and the cost would have been 54% lower than a policy of full karyotyping for all. CONCLUSIONS: Detailed prenatal ultrasound scan can reduce the need for conventional karyotyping as a complement to QF-PCR in most prenatal samples, offering rapid results and reducing parental anxiety and healthcare costs.