Quantitative fluorescent polymerase chain reaction versus cytogenetics: risk-related indication and clinical
P Kozlowski1, I Grund, G Hickmann
1Praenatal-Medizin und Genetik Dusseldorf, Dusseldorf, Germany. kozlowski@praenatal.de
Background:
The rapid detection of aneuploidies by quantitative fluorescent polymerase chain reaction (QF-PCR) allows reliable prenatal diagnosis of trisomies 21, 18, and 13. Discussion has been raised as to whether single QF-PCR could be an alternative to traditional cytogenetic karyotyping for certain referral categories.
Objective:
To evaluate an indication-based classification of cases at risk of missing clinically relevant chromosomal disorders by QF-PCR.
Methods:
From October 1999 to November 2003, 4,682 of 14,123 patients referred for amniocentesis decided to have QF-PCR as a rapid adjunct to conventional cytogenetic evaluation. Patients were classified according to the risk of missing chromosomal abnormalities by QF-PCR based on anamnestic risk and ultrasound prior to amniocentesis. The results in these two defined categories were compared in relation to the clinical significance of cytogenetic results.
Results:
QF-PCR and conventional cytogenetic analysis had concordant results in 4,617 of 4,682 (98.6%) cases. Thirty-six of 110 (32.2%) clinically significant chromosomal abnormalities were missed by QF-PCR. Patients classified not to be at risk of missing chromosomal abnormalities using QF-PCR had a residual risk of 1/166 (0.6%) for chromosomal distortions of clinical significance.
Conclusion:
Classification by anamnestic and sonographic data does not specifically identify patients at risk of structural abnormalities. Clinical relevance of the nondetected anomalies essentially justifies traditional karyotyping regardless of risk classification.
