1. University of Vermont Larner College of Medicine, Burlington, Vermont, USA
2. Department of Biostatistics, University of Alabama at Birmingham, Birmingham, Alabama, USA
3. Department of Medicine, University of Vermont Larner College of Medicine, Burlington, Vermont, USA
4. SphingoTec GmbH, Hennigsdorf, Germany
5. Department of Pathology and Laboratory Medicine, University of Vermont Larner College of Medicine, Burlington, Vermont, USA