From the Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City (Dr Krasowski); the Department of Pathology, University of Utah School of Medicine, ARUP Laboratories, Salt Lake City (Dr McMillin); the Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts (Dr Melanson); the Proficiency Testing Division, College of American Pathologists, Northfield, Illinois (Ms Dizon); the Department of Pathology and Laboratory Medicine, Tufts Medical Center, and Department of Anatomic and Clinical Pathology, Tufts University School of Medicine, Boston, Massachusetts (Dr Magnani); and the Department of Laboratory Medicine and Pathology, Mayo Clinic in Arizona, Scottsdale (Dr Snozek).