Cribado combinado de síndrome de Down en primer trimestre: comparación de resultados de 4 años de aplicación con los 4 años precedentes

Objective

To analyze the 4-year results of first-trimester combined screening and its impact on rates of Down syndrome detection, population coverage and invasive procedures.

Subjects and methods

We performed a retrospective population-based study over 8 consecutive years (17,564 gestations with 51 cases of Down syndrome) divided in two periods: from January 31, 2002 to January 30, 2006 without combined screening (8,182 gestations and 24 cases of Down syndrome) and from January 31, 2006 to January 30, 2010 with combined screening (8,382 gestations and 27 cases of Down syndrome). Combined screening was applied in two phases: biochemical analysis was performed in the 10th week of pregnancy and ultrasound examination in the 12th week. We compared the results of screening with the previous period based on maternal age and fetal nuchal translucency measurement.

Results

Population coverage was 93%. The rate of Down syndrome detection due to the application of combined screening was 89% (91% for a single fetus) with a false-positive rate of 3.5%. There were 824 invasive procedures (34.1 to diagnose one episode). During the 4 years prior to the application of combined screening, the detection rate was 71% with 1,406 invasive procedures (87.8 to diagnose one episode).

Conclusion

Combined screening has improved the Down syndrome detection rate by 18% and has reduced the use of invasive procedures by 41%.