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NADINE WEISSCHER, CARLA A. WIJBRANDTS, ROB de HAAN, CEES A.W. GLAS, MARINUS VERMEULEN, and PAUL PETER TAK
ABSTRACT. Methods. 129 patients with RA completed the ALDS and Health Assessment Questionnaire Disability Index (HAQ-DI) at baseline, and after 8 and 16 weeks of anti-tumor necrosis factor-a treatment. Disease activity assessments at these timepoints included serum levels of C-reactive protein, Disease Activity Score 28, morning stiffness, and visual analog scales for global disease activity and fatigue. Results. Reliability of the ALDS was excellent (homogeneity, Cronbach's a = 0.95; test-retest, intraclass correlation coefficient = 0.93). The ALDS results at baseline were strongly correlated with the HAQ-DI (r = –0.75). With regard to known group validity, both instruments discriminated between higher and lower disease activity (ALDS, p < 0.0001; HAQ-DI, p = 0.002) and between non-, moderate, and good responders (ALDS, p = 0.002; HAQ-DI, p < 0.0001), indicating that both instruments differentiate between groups. The ALDS was moderately to highly responsive to changes between baseline and after 8 weeks and 16 weeks of treatment (standardized response mean, range = 0.71–1.19). No substantial floor or ceiling effects were found. Conclusion. Our results show that the ALDS is a promising new instrument, with at least equivalent psychometric properties compared to the HAQ-DI. Advantages of the ALDS item bank are its linear structure and an item bank that can be adapted depending on the ability level of the patient. (J Rheumatol 2007;34:1222-8) Key Indexing Terms:
DISABILITY
From the Department of Neurology, Division of Clinical Immunology and Rheumatology, Department of Clinical Epidemiology and Biostatistics, Academic Medical Center, University of Amsterdam; and Department of Educational Measurement, University of Twente, Enschede, The Netherlands. N. Weisscher is supported by a grant from the Academic Medical Center — the Anton Meelmeijer Fonds. C.A. Wijbrandts is supported by a grant (no. 945-02-029) from The Netherlands Organization for Health Research and Development (ZonMw), and the Dutch Arthritis Association. N. Weisscher, MSc, Department of Neurology; C.A. Wijbrandts, MD; P.P. Tak, MD, PhD, Division of Clinical Immunology and Rheumatology; R.J. de Haan, PhD, Department of Clinical Epidemiology and Biostatistics; M. Vermeulen, MD, PhD, Department of Neurology, Academic Medical Center, University of Amsterdam; C.A.W. Glas, PhD, Department of Educational Measurement, University of Twente. Address reprint requests to N. Weisscher, Department of Neurology, H2-236, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands. E-mail: n.weisscher@amc.uva.nl Accepted for publication February 8, 2007. |
