Antenatal maternal serum screening for Down's syndrome: results of a demonstration project.

Abstract

Conclusion -Antenatal maternal serum screening for Down's syndrome is effective in practice and can be readily integrated into routine antenatal care. It is cost effective and performs better than selection for amniocentesis on the basis of maternal age alone.

Authors' Reply

“…Table 2 shows the current performance achieved in prospective practice. We believe these screening performance figures confirm our predictions based on our retrospective study, especially when compared with the prospective performance achieved by Wald et al 16 of 48% detection and the 58% detection achieved by Haddow et al 17 using 'triple screening'. In summary, Wald et al offer comments on our paper based on theory.…”

“…2 that the proportion of cases greater than 2 MoM are higher at gestations greater than 16 weeks and suggest that this is directly opposite to those we stated in Table 9. 1 Wald et al misunderstand the data in Table 9, which contains detection rate data based on the use of three parameters-maternal age, o-fetoprotein (AFP) and free (3 hCG concentrations; this data cannot be directly compared with Fig.…”

“…However, on re-examination on Fig. 2 and its associated data we did find that this figure contained two errors: there are 91 points plotted rather than the 90 that should be and two cases plotted at 16 weeks should have been at 17 weeks.…”

“…Even though they could have presented empirical data they chose not to do so. The 60% detection efficiency resulting from this model was promoted as a benchmark for 'triple screening' , although even Wald et al 16 have not found this achievable in practice.…”

“…When the actual data is examined, the median Free (3-hCG in Down's syndrome cases at the [14][15][16] weeks' gestation period was 2·52 and at greater than 16 weeks was 2' 32. The corresponding median for AFP in these two groups was o· 66 and 0'73 and the mean age was 30·9 and 30'2 years, respectively.…”