From the *Arthritis and Rheumatism Council Epidemiology Research Unit, School of Epidemiology and Health Sciences, University of Manchester, England, the †School of Postgraduate Medicine, University of Keele, England, and the ‡Rheumatic Diseases Centre, University of Manchester, England.
This research was supported by the Arthritis and Rheumatism Council, Chesterfield, and the National Back Pain Association, Teddington, United Kingdom.
Acknowledgment date: March 21, 1996.
First revision date: July 15, 1996.
Acceptance date: September 1, 1996.
Device status category: 1.
Address reprint requests to Gary J. Macfarlane, PhD; Arthritis and Rheumatism Council Epidemiology; Research Unit; School of Epidemiology and Health Sciences, University of Manchester; Stopford Building, Oxford Road; Manchester M13 9PT, England