1. Institute for Hygiene, University of Münster, Robert-Koch-Strasse 41, D-48149 Münster, Germany, Sequenom GmbH, Mendelssohnstrasse 15 d, 22761 Hamburg, Germany, and Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Strasse 31, D-48149 Münster, Germany