1. From the National Heart and Lung Institute (J.C.C., Y.K., J.S.K.) and the Department of Medical Statistics and Evaluation (P.B., S.G.T.), Imperial College School of Medicine, Hammersmith Hospital, London, UK; F. Hoffmann-La Roche & Co Ltd, Basel, Switzerland (S.E.); and the Department of Medicine, Royal Free and University College Medical School, London, UK (J.R.G., M.B.P.).