Down's syndrome: absence of nasal bone may be marker
30 November 2001
Screening fetuses at 11 weeks for the presence of a nasal bone could dramatically reduce the need for invasive testing for Down's syndrome, a UK study has found.
Sydney's Royal North Shore Hospital's consultant in foetal medicine Dr Andrew McLennan has welcomed the research, saying the results were an exciting development.
'I've just looked at the films of my last 3 proven Down's syndrome babies on the basis of the results and found they've all got absent nasal bone,' he said.
'I'm not usually excited by new markers because they never prove to be as good as you first thought, but this looks like it has something - the numbers are really quite extraordinary.'
In the study, reported in the British medical journal Lancet (2001;358:1665-67), researchers examined the profiles of 701 fetuses between 11 and 14 weeks' gestation and with possible chromosomal defects.
The nasal bone was absent in 73 per cent of fetuses with Down's syndrome (43 of 59) and in 0.5 per cent of chromosomally normal fetuses (3 of 603). Another 11 of 20 fetuses with trisomy 18 (known as Edward's syndrome) and 2 of 8 fetuses with Turner's syndrome did not have a nasal bone present.
None of those with the chromosome abnormalities trisomy 13, triple X syndrome, Klinefelter's syndrome or triploid, had a nasal bone visible.
'The prediction with these results is that they will improve the detection rate towards 90 per cent or beyond and potentially drop the positive rate down to hopefully 2 or 3 per cent,' Dr McLennan said.
Last Reviewed: 27 November 2001
- Medical Observer Weekly 30 November 2001
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