 Nuchal scanning alone detects 62% of all Down syndrome (sensitivity) with a false positive rate of 5.0%; the combination with blood testing gives corresponding values of 73% and 4.7%.In another study values of 79.6% and 2.7% for the combined screening were then improved with the addition of second trimester ultrasound scanning to 89.7% and 4.2% respectively.A further study reported detection of 88% for trisomy 21 (Down syndrome) and 75% for trisomy 18 (Edwards syndrome), with a 3.3% false-positive rate.