Identification of disease activity and health status cut points for the symptom state acceptable to rheumatoid arthritis patients

Turid Heiberg ^1*, Tore Kristian Kvien ², Petter Mowinckel ³, Daniel Aletaha ⁴, Josef S Smolen ⁵ and Kåre Birger Hagen ³

¹ Dept of Research and Education, Ullevål University Hospital, N-0407 Oslo, Norway
² Dept of Rheumatology, Diakonhjemmet Hospital, 0319 Oslo, Norway
³ Dept of Rheumatology, Diakonhjemmet Hospital, N-0319 Oslo, Norway
⁴ Medical University of Vienna, Vienna, Austria
⁵ Hietzing Hospital and Medical University of Vienna, Vienna, Austria

^* To whom correspondence should be addressed. E-mail: turid.heiberg{at}studmed.uio.no.

Accepted 13 October 2007

Abstract

Objective: Established thresholds for low levels of disease activity need to be examined in the context of the patients’ perspective. The aims of this study were to identify new cut points for patients’ perception of satisfactory condition (Patient Acceptable Symptom State (PASS)) in composite indices and patient reported outcomes, and to examine the agreement between the new PASS cut points for composite indices and existing thresholds for remission, low and moderate disease activity.

Methods: Cases with rheumatoid arthritis (RA) from a treatment register (n=1496, 72.1 % females, mean (SD) age 53.9 (13.5), disease duration 7.6 (9.1), DAS28 4.98 (1.36)) responded during follow-up (12, 24 and 52 weeks) to a global dichotomized question on satisfactory condition (PASS). New PASS cut points were identified with the 75th centile estimation and ROC analyses for a variety of outcome measures and cut points for composite indices were examined for agreement with the low disease activity threshold (1.625) of the Patient Activity Scale (PAS) and thresholds for remission, low and moderate disease activity in DAS28, SDAI and CDAI.

Results: New PASS cut points for DAS28, SDAI and CDAI were in the moderate range of disease activity, and was 3.56 for PAS. Agreement between thresholds for disease activity levels and the PASS cut points was best for low disease activity (accuracy 64.5-74.6), and better for moderate disease activity (accuracy 61.3-67.2) than for remission (accuracy 30.7-45.8).

Conclusion: The current PASS concept seems to be in the range of moderate disease activity.

Keywords: Patient Acceptable Symptom State (PASS), arthritis, rheumatoid, composite indices, outcome measures, patient perspective

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