ASSESSMENT OF ENTHESITIS IN ANKYLOSING SPONDYLITIS

Background: Enthesitis is a primary clinical feature in ankylosing spondylitis (AS).In 1987, Mander et al. published an instrument to investigate enthesitis in AS (Mander enthesis index=MEI).Objectives: The aim of this study was first to assess the validity of the enthesis index published by Mander and second whether it is possible to define a new enthesis index that is less time consuming to perform with at least similar or better validity.Methods: Data from the OASIS cohort, an international, longitudinal, observational study on outcome in AS, were used. In this study, measures of disease activity, among which the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the MEI, were assessed regularly in 217 patients. With regard to the MEI, a process of data-reduction was performed to identify the entheses most frequently scored as painful. The result was used to construct a more concise enthesis index. Using correlations with measures of disease activity tested the validity of several entheses indices.Results: Reduction of the number of entheses from 66 to 13 and omitting grading of the intensity of pain resulted in an index that we called Maastricht Ankylosing Spondylitis Enthesis Score=MASES. The MASES (range 0-13) has much greater feasibility compared to the MEI (range 0-90), however, up to 21% of patients with a score >0 on the MEI were not identified by a score on the MASES >0. Only 2.1% of the patients with an original enthesis score > 0 had an original score on the MEI > 3 (range 0-90) and it can be questioned whether a low sore on the MEI index represents clinically important enthesitis. Spearman Correlation coefficient between the MASES score and the MEI was 0.90 and between the MASES and the BASDAI was 0.53 compared to a correlation of 0.59 between the MEI and the BASDAI.Conclusion: MASES seems to be a good alternative to the Mander enthesis index. Further evaluation of sensitivity to change will be undertaken.Citation: , volume , supplement , year 2002, page Session: Spondylarthropathies including psoriatic arthritis 2