1. Department of Chemistry, University of Jyväskylä, FIN-40351 Jyväskylä, Finland, Department of Clinical Chemistry, Tampere University Hospital and University of Tampere Medical School, P.O. Box 2000, FIN-33521 Tampere, Finland, Department of Chemistry, University of Turku, FIN-20014 Turku, Finland, and PerkinElmer Life Sciences, Wallac Oy, P.O. Box 10, FIN-20101 Turku, Finland