Desirable quality-control materials for the establishment of qualified external quality assessment on prenatal diagnosis of chromosomal aneuploidies

Abstract

Objective: To prepare desirable quality-control materials for the establishement of qualified external quality assessment on fluorescence in situ hybridization (FISH)-detected prenatal diagnosis of chromosomal aneuploidies.

Methods: Four types of amniotic fluid cell suspensions (13-trisomy, 18-trisomy, 21-trisomy and 47,XXY) were mixed together by ratio to produce mosaicism with the percentages of each aneuploidy as 10%, 20%, 30% and 40%, respectively. After being stored in liquid nitrogen of -196 °C for six months, randomly selected samples were incubated in 37 °C water, followed by cultivation, hypo-osmosis and fixation. Finally, FISH detetion was applied on them before and after external laboratory mailing, in step with detection on conventional case samples.

Results: Before mailing, the positive rates of each aneuploidy described above were 12.8%, 23.6%, 33.8%, 44.0%, while 12.6%, 23.8%, 34.0%, 43.5% after mailing. t-test, criteria for stability assessment of quality-control materials in CANS-GL03:2006, showed no significant effect of external mailing on mosaicism since corresponding t values are lower than threshold with significance level α as 0.05 and degree of freedom as 10.

Conclusion: As FISH detection showed, the mosaic cell strains prepared in current study exhibited excellent stabilities after cryopreservation in -196 °C, subculture, hypo-osmosis, fixation and external laboratory mailing, demonstrating them as reliable and promising quality-control materials for the establishment of a qualified external quality assessment on prenatal diagnosis of chromosomal aneuploidies.

Keywords: Chromosomal aneuploidies; External quality assessment; Fluorescence in situ hybridization; Prenatal diagnosis; Quality control materials.