OP17 .04: Unintended consequences of UK guidance for anomaly screening and invasive testing

Le résumé fourni par la source

To assess clinically important discrepancies between FISH/QFPCR and karyotype arising following prenatal invasive testing in one region. This follows a restriction in the routine use of full karyotype, and the downgrading of 'soft markers' as not warranting detailed ultrasound. From 2008–2012, we reviewed 2717 invasive tests performed following trisomy 21 (T21) screening risk >1:250. Routine karyotype was performed until new UK guidance in 2012. In 11 cases there was a discrepancy between FISH/QFPCR & karyotype. In one, QFPCR gave an incorrect result for a major trisomy. Based on early ultrasound findings and subsequent scan where soft markers would have been ignored there were 10 cases where FISH/QFPCR alone but not karyotype was performed and clinically important diagnoses would have been missed (table). In none was there a detectable major structural abnormality on ultrasound. Rapid antenatal diagnosis is cost effective if the aim of the invasive testing is to detect trisomies only but risks overlooking rare but potentially devastating chromosomal abnormalities, especially if soft markers are ignored as an indication for referral. Further, the rare discrepancy between QFPCR and Karyotype for T21 is reported as 0.1%. Though these risks are small, if prenatal testing is to provide autonomy of reproductive choice rather than testing only for trisomies, current guidance may result in more births where there is unanticipated major disability.

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