Calculation of roc curves in multidimensional likelihood ratio based screening with Down's syndrome as a special case

Objectives-The development of algorithms and computer programs for the analysis of screening performance in situations with multiple normally (Gaussian) distributed selection markers and a priori risks depending on a stratification of the population. Methods-The S-PLUS programming language was used to construct programs producing distributions of log likelihood ratios based on the Monte Carlo simulation. These distributions were used to construct programs for the calculation of roc curves, including a possible stratification of the population. Results-S-PLUS programs for the analysis of screening performance are listed and described. The programs can be used without any special knowledge of S-PLUS. An example of the use of the programs is given.