Trends in cytogenetic prenatal diagnosis in the UK: results from UKNEQAS external audit, 1987-1998.

The aim of this audit was to evaluate trends in mean reporting time, culture success rate and abnormality rate for conventional cytogenetic prenatal diagnoses for amniotic fluid samples (AFS) and chorionic villus samples (CVS) in the UK. Anonymized data in the form of retrospective external audits were obtained from UKNEQAS in Clinical Cytogenetics annual reports, for AFS (1987-1997/98) and CVS (1988-1997/98). UK laboratories providing a prenatal service by referral criteria applicable at local level participated in the scheme. Over the period the number of AFS processed per annum increased from 28 639 to 36 817 (29 per cent) and for CVS from 2294 to 7918 (245 per cent). CVS made up 17.6 per cent of the total sample numbers in 1997/98 compared with 7.4 per cent in 1988. Reporting times and culture success rates have improved, notably overall reporting time means have fallen from 20.2 to 13.8 days for AFS and 21.3 to 14.5 days for CVS. Data submitted by individual laboratories suggest that further reductions in mean reporting times for both sample types are feasible. Such a potential improvement, if achieved by all laboratories, may question the value of a supplementary FISH or PCR-based 'rapid' aneuploidy screening test prior to karyotyping. Copyright 1999 John Wiley & Sons, Ltd.