1. Section of Pulmonary and Critical Care Medicine, Yale University School of Medicine, Department of Internal Medicine, 300 Cedar Street, TAC S-441, New Haven, CT 06520–8057, USA.
2. Department of Pathology, Yale University School of Medicine, 310 Cedar Street, 108 LH, New Haven, CT 06520–8057, USA.
3. Pathology and Laboratory Medicine Service, VA-CT Health Care System, 950 Campbell Avenue, West Haven, CT 06516, USA.
4. Meakins-Christie Laboratories, 3626 Saint Urbain, McGill University, Montreal, Quebec, H2X 2P2, Canada.