External quality assessment of prenatal diagnosis of a rare and subtle chromosomal structural abnormality

B.-H. Weng, Y.-E. Lu, X. Li

Women’s Reproductive Health Laboratory of Zhejiang Province, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China. lixsure@163.com

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• Genetics

PURPOSE OF THE STUDY: To explore the misdiagnosis probability of subtle chromosomal structural abnormalities and find proper strategy to improve the accuracy of prenatal genetic diagnosis, we carried out a preliminary external quality assessment of prenatal detection of a rare case.

PATIENTS AND METHODS: Three karyograms of a rare case of cri du chat syndrome associated with t(11;22) translocation [46,XY, del(5)(p15.2), t(11;22)(q23;q11.2)] were chosen. The patient’s information and karyograms were emailed to 21 laboratories simulating the scenarios of prenatal diagnosis. The laboratories were required to provide a report using current nomenclature.

RESULTS: Seven laboratories sent results for evaluation (response rate: 33.33%). For t(11;22), Two labs incorrectly reported that chromosome 22 was deletion. 5 of 7 labs reported t(11;22) translocation consistent with the actual karyotype. Among them, lab 6 suspected the abnormal 5q and lab 7 incorrectly considered chromosome 22 was deletion or reduplication. All laboratories missed to report the karyotype of del(5).

CONCLUSIONS: Conventional cytogenetic analysis couldn’t always detect subtle chromosomal structure abnormalities correctly during prenatal diagnosis. To improve the quality of prenatal genetic diagnosis, an excellent external quality assessment (EQA) scheme is currently imperative in China.

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