Multiplex ligation-dependent probe amplification: a reliable and cost efficient ‘single-test’ alternative for fetal chromosome analysis?

Objective To evaluate multiplex ligation-dependent probe amplification (MLPA) as an alternative for rapid, accurate diagnosis of fetal chromosomal abnormalities. Background Traditionally fetal chromosome analysis is performed by full karyotyping, detecting most clinically significant abnormalities, but taking 2–3 weeks. Rapid testing (qfPCR) detecting only major trisomies and triploidy is also offered in most UK units. MLPA is a rapid molecular test used postnatally which may detect abnormalities not identified by full karyotyping or qfPCR. Methods MLPA probes designed to test for subtelomeric changes and microdeletion syndromes with well-defined phenotypes were used. Women undergoing karyotyping for clinical indications were asked for informed consent to use MLPA to test excess chorionic villi or amniocytes remaining after clinical testing. Results obtained using qfPCR, karyotyping and MLPA were compared. Results Of the 523 samples tested MLPA was inconclusive in 56 (10.7%), mainly due to insufficient DNA being available. Triploidy was not detected by MLPA. Of the 35 other rearrangements 10 were only detected by karyotyping, of which 3 were balanced and 7 were mosaics, 8 by MLPA alone and 17 by both. Overall, 24 of these 35 rearrangements conferred a significant risk of adverse outcome; 15 were detected by both karyotyping and MLPA, 6 only by MLPA and 3 by karyotyping alone. Conclusion MLPA is potentially a rapid alternative for full karyotyping but requires further evaluation and comparison with other molecular methods.