The prevalence of non-detectable chromosomal abnormalities by QF-PCR in amniocentesis for certain referral indications: experience at a mainland Chinese hospital.

Purpose: To study the prevalence of non-detectable chromosomal abnormalities by quantitative fluorescent polymerase chain reaction (QF-PCR) in a Chinese population referred for amniocentesis.

Methods: The karyotype results were reviewed in 8,466 amniotic fluid cultures performed for positive fetal Down syndrome screening or advanced maternal age between January 2002 and June 2012. The karyotype results were classified as detectable or not detectable by QF-PCR, using the assumption that all tests were conducted by this rapid molecular method.

Results: Of the 8,466 karyotypes obtained, 211 abnormal karyotypes were found (2.5%). Out of these, 168 cases of common aneuploidies were identified by QF-PCR, and 43 cases of chromosomal abnormalities were missed. The 43 cases missed by QF-PCR included 31 cases predicted to confer no increased risk and 12 with a potential clinical significance. When QF-PCR shows a normal result, the overall residual risk is 0.1% for any clinically significant chromosomal abnormality.

Conclusions: A normal QF-PCR result predicts a very low residual risk for patients who are referred solely for an increased risk of a common trisomy.