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Objective To compare the efficacy of fetal nuchal translucency screening, maternal serum screening and combined screening for Down syndrome. Design A prospective study. Setting University hospital and its public health care district in Northern Finland. Population A total of 35 314 women participated in the first-trimester screening for Down syndrome within the public healthcare system in 2002-08. There were 95 pregnancies involving Down syndrome. Serum samples were obtained from 35 314 women, nuchal translucency was measured in 27 144 pregnancies and full combined screening was performed in those pregnancies, including 76 involving Down syndrome. Methods The adjusted estimated risk for Down syndrome was calculated using the Perkin Elmer Auto DELFIA® time-resolved fluoroimmunoassay kit for the measurement of pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin. Nuchal translucency was measured by trained personnel in a university or district hospital. Risk cut-off figures 1:250 and 1:300 at term were used. Main outcome measures Differences in detection rate, false-positive rate, positive and negative predictive values between nuchal translucency screening, serum screening and combined screening. Results Using the risk cut-off figure 1:250, the detection rates for serum screening, nuchal translucency screening and combined screening were 64.2, 64.5 and 72.4%, respectively and the false-positive rates were 7.8, 4.4 and 4.0%, respectively. Conclusions Combined screening is the method of choice for Down syndrome screening in Finland. [ABSTRACT FROM AUTHOR]

Objectives We evaluated the performance of first trimester screening for Down syndrome in women less than 35 years of age (study group) and in women aged 35 years or more (control group) in an unselected low-risk population. Methods The study group comprised a total of 63 945 women who participated in the first trimester combined screening in public health care in Finland during the study period of 1 May 2002 to 31 December 2008. Women at the age of 35 or more ( n = 13 004) were controls. Prevalence of Down syndrome, detection rate, false positive rate and number of invasive procedures needed to detect a single case of Down syndrome were analyzed in both groups. Results The overall prevalence of Down syndrome ( n = 73) in the study group was 1:876. The number of detected cases was 54. The detection rate was 74.0% with a false positive rate of 2.8%. Number of invasive procedures needed to detect a single case of Down syndrome was 33. In the control group, the detection rate was 87.0% with a false positive rate of 11.9%. The number of invasive procedures needed to detect a single case of Down syndrome was 15. The differences in detection rate and false positive rate were significant, P < 0.012, P < 0.001, respectively. Conclusion The overall detection rate given for the entire population is an overestimate for a woman younger than the age of 35, which should be taken into consideration when counselling women of that age. [ABSTRACT FROM AUTHOR]