Clinical Significance of Conventional Karyotype and QF-PCR in Detection of Fetal Chromosomal Abnormalities

Abstract

This study aims to compare the advantages of two widely used methods for fetal chromosomal detection, karyotyping and QF-PCR, together with the indications for invasive prenatal diagnosis. We retrospectively investigated 888 amniocenteses analyzed by karyotyping only or karyotyping combined with QF-PCR. We assessed the results of each method and compared them to the indications for prenatal testing including maternal age, fetal ultrasound findings, and serum screening. We found 39 (4.4%) abnormalities, where 59% of those abnormalities were numerical and 41% were structural abnormalities undetectable by QF-PCR methods. Many structural abnormalities do not have clinical significance and we found that 23% of found structural abnormalities were clinically significant but undetectable by QF-PCR (0.3% of all amniocentesis analyzed). Additional 23% of found structural abnormalities were balanced translocations which can have rare clinically significant consequences. In total, 46% of found structural abnormalities had possible clinical consequences, which were undetectable by QF-PCR, or by noninvasive prenatal testing for five common aneuploidies. Thus, QF-PCR is a reliable method to detect most common fetal aneuploidies, but karyotyping should be used if any other chromosomal abnormalities are suspected. Even though QF-PCR is a fast and reliable method, physicians should be aware of the limitations of various methodologies for detection of fetal abnormalities and assign the proper method to the indication for amniocentesis.