Comparison of Internal and External Responsiveness of the Generic Medical Outcome Study Short Form-36 (SF-36) with Disease-specific Measures in Rheumatoid Arthritis

MARTINE M. VEEHOF, PETER M. ten KLOOSTER, ERIK TAAL, PIET L.C.M. van RIEL, and MART A.F.J. van de LAAR

ABSTRACT.

Objective. To examine the comparative internal and external responsiveness of the generic Medical Outcome Study Short Form-36 Health Survey (SF-36) and disease-specific measures in patients with rheumatoid arthritis (RA).

Methods. Data were collected from 280 RA patients starting anti-tumor necrosis factor treatment. A total of 168 patients completed a questionnaire including the SF-36, the Arthritis Impact Measurement Scales 2 (AIMS2), the Health Assessment Questionnaire (HAQ), a visual analog scale for general health (VAS-GH), and an 11-point numerical rating scale for pain (NRS pain) at baseline and after 12 months. Internal responsiveness was evaluated with paired samples t-tests and standardized response means (SRM). External responsiveness was investigated with receiver-operating characteristic statistics and Spearman rank-order correlation coefficients. A health transition item was used as the external indicator of change.

Results. No significant differences in internal and external responsiveness were found between the SF-36 and disease-specific measures within the domains physical function, pain, and psychological function. In the domain social function, the SF-36 was more responsive than the AIMS2. In the domain general health, the SF-36 was less responsive (only internal) than the AIMS2 and VAS-GH.

Conclusion. Our study showed comparable internal and external responsiveness of the SF-36 compared with disease-specific measures (AIMS2, HAQ, NRS pain) in all health domains, except social function and general health domains. The assumption that disease-specific measures are more responsive to detect intervention-related changes over time is not confirmed by our data. (J Rheumatol First Release Mar 1 2008)

Key Indexing Terms:

RHEUMATOID ARTHRITIS
HEALTH-RELATED QUALITY OF LIFE
OUTCOME MEASURES
RESPONSIVENESS

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From the Institute for Behavioral Research, University of Twente, Enschede; Department of Rheumatology, Radboud University Nijmegen Medical Centre, Nijmegen; and Department of Rheumatology, Medisch Spectrum Twente, Enschede, The Netherlands.

Funded by an unrestricted educational grant by Schering-Plough and CVZ (Health Care Insurance Board).

M.M. Veehof, MSc, OT, University of Twente; P.M. ten Klooster, MSc, University of Twente; E. Taal, PhD, University of Twente; P.L.C.M. van Riel, MD, PhD, Professor, Radboud University Nijmegen Medical Centre; M.A.F.J. van de Laar, MD, PhD, Professor, University of Twente and Medisch Spectrum Twente.

Address reprint requests to M.M. Veehof, Institute for Behavioural Research, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. E-mail: m.m.veehof@utwente.nl

Accepted for publication November 14, 2007.