1. Department of Surgery, University of California, San Francisco-East Bay, 1411 E 31st Street, QIC 22134, Oakland, CA 94602, USA
2. Biostatistical Consulting Unit, Division of Research, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA 94612, USA
3. Division of Thoracic Surgery, Department of Surgery, Kaiser Permanente Northern California, 3600 Broadway, Oakland, CA 94612, USA
4. Department of Surgery, University of California, San Francisco School of Medicine, 533 Parnassus Ave, San Francisco, CA 94143, USA
5. Department of Clinical Medicine, Kaiser Permanente Bernard J. Tyson School of Medicine, 98 S Los Robles Ave, Pasadena, CA 91101, USA