Rheumatology Advance Access originally published online on March 5, 2008
Rheumatology 2008 47(4):514-518; doi:10.1093/rheumatology/ken004
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Disease Activity Score 28-ESR bears a similar relationship to treatment decisions across different rheumatologists, but misclassification is too frequent to replace physician judgement
1University of Otago, Wellington, 2Wellington Regional Rheumatology Unit, Hutt Valley District Health Board, Lower Hutt, 3University of Otago, 4Otago District Health Board, Dunedin, 5Canterbury District Health Board, 6University of Otago, Christchurch, 7University of Auckland, Auckland, 8QE Health, Rotorua, 9South Canterbury District Health Board, Timaru, 10Nelson-Malborough District Health Board, Nelson, 11Wanganui District Health Board, Wanganui, 12Counties-Manukau District Health Board, Auckland and 13193 Memorial Avenue, Christchurch, New Zealand.
Correspondence to: W. J. Taylor, Department of Medicine, University of Otago Wellington, PO Box 7343, Wellington 6242, New Zealand. E-mail: will.taylor{at}otago.ac.nz
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Abstract |
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Objectives. To determine whether physician factors are associated with disease activity status in RA, independently of 28-joint disease activity score (DAS28)-ESR and to re-evaluate DAS28-ESR misclassification rates for identifying active disease in usual practice.
Methods. A prospective observational study of outpatients with RA seen by 17 rheumatologists across New Zealand. Active disease was defined by an increase in therapy together with a reason of ‘active disease’; very low disease activity was defined by a decrease in therapy together with a reason of ‘patient well’. The independent physician effect was assessed using logistic regression. Sensitivity and specificity of current DAS28-ESR thresholds were calculated.
Results. In 511 patients, 178 had active disease, 220 had low disease activity, 37 had very low disease activity and 76 had uncertain disease activity status. There was no independent effect of physician upon active disease status (P = 0.16) with DAS28-ESR [(OR) 3.7] explaining around 50% of the variability in active disease status. There was a trend towards an independent effect of physician upon very low disease activity status (P = 0.06) and greater variability in the distribution of DAS28-ESR for patients in very low disease activity. DAS28-ESR thresholds showed a significant risk of misclassification for active disease.
Conclusions. DAS28-ESR discriminates satisfactorily between groups of patients with active and non-active disease, with no evidence of additional physician-specific factors to explain disease activity status. However, DAS28-ESR is not as good for discriminating remission from non-remission status. There are appreciable probabilities of misclassification error, which make DAS28-ESR inappropriate as a sole guide for treatment decisions.
KEY WORDS: Rheumatoid arthritis, Disease activity score, Remission criteria, Reliability, Validity, Health status, Treatment decisions, Psychometrics, Physician-factor, Methodology
Submitted 31 October 2007;
revised version accepted 3 January 2008.
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