An algorithm for the prenatal detection of chromosome anomalies by QF-PCR and G-banded analysis.
OBJECTIVE
The objective of this study was to examine in theory the clinical utility of a prenatal algorithm that uses rapid aneuploidy detection in all cases and G-banded analysis for selected cases (RAD/G algorithm).


METHODS
Over a 4-year period, amniotic fluid samples were prospectively assigned into RAD (limited analysis) or RAD/G (intensive analysis) categories based upon the likelihood of the fetus having a chromosome anomaly. The samples were cultured and analyzed by standard cytogenetic methods. The rates of clinically significant chromosomal anomalies potentially undetectable by the RAD/G algorithm were calculated.


RESULTS
The karyotype was normal in 3861/4054 (95.24%) cases and abnormal in 193 (4.76%). From these data, the detection rate of the RAD/G algorithm was 87.6% if all abnormalities detected by G-banding were taken into consideration and 97.6% if abnormalities having reduced predictive value were excluded (balanced rearrangements and most mosaic cases).


CONCLUSIONS
Compared to G-banding alone, the RAD/G algorithm has a reduction in sensitivity due to undetectable abnormalities and mosaicism in the RAD group. However, it provides a rapid and inexpensive alternative to traditional G-banded analysis, and might be more appropriate for patients with uncomplicated, low risk pregnancies.
Speevak
M D
MD
Genetics Division, Department of Laboratory Medicine, Credit Valley Hospital, Mississauga, Canada. mspeevak@cvh.on.ca
Dolling
J
J
Terespolsky
D
D
Blumenthal
A
A
Farrell
S A
SA
D000465:Algorithms; D000782:Aneuploidy; D002871:Chromosome Banding / Q000379:methods; D005260:Female; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D011446:Prospective Studies