NOMOGRAMS TO HELP INFORM WOMEN CONSIDERING DOWNS-SYNDROME SCREENING

Objective: To derive graphical information for use in counselling wome n considering whether or not to have maternal serum screening for Down 's syndrome. Design: Statistical modelling of the frequency distributi on of estimated Down's syndrome risk for four marker combinations. Res ults: Nomograms are provided showing for each maternal age: (a) the de tection and false-positive rates, and (b) the proportion of pregnancie s with different estimated risks. Conclusion: When screening is offere d, clinicians need to have information readily available on test accur acy and the likely result, which is specific to the individual.