1. From the Institute for Technology Assessment, Massachusetts General Hospital, Boston (A.A., P.C.E., C.H.)
2. Department of Medicine, Massachusetts General Hospital, Boston (A.A., P.C.E., C.H.)
3. Department of Emergency Medicine, Massachusetts General Hospital, Boston (K.S.Z.)
4. Harvard Medical School, Boston, MA (K.S.Z., P.C.E., L.H.S., C.H.).
5. Department of Neurology, Massachusetts General Hospital, Boston (L.H.S.)