Measuring clinical enthesitis in psoriatic arthritis: assessment of existing measures and development of an instrument specific to psoriatic arthritis.
OBJECTIVE
To assess currently available tools for measurement of enthesitis and to develop a new instrument specifically for use in psoriatic arthritis (PsA).


METHODS
Twenty-eight patients with PsA underwent clinical assessment over a period of 6 months after change of disease-modifying therapy, usually to methotrexate. Measures of enthesitis included the Mander Enthesitis Index (MEI), the Maastricht Ankylosing Spondylitis Enthesitis Score, the Major index, and the Gladman index. Data from these assessments were used to develop a new enthesitis index, the Leeds Enthesitis Index (LEI).


RESULTS
An iterative process of data reduction enabled derivation of the LEI index, which consisted of 6 sites: right and left Achilles insertions, medial femoral condyles, and lateral epicondyles of the humerus. All measures showed significant change from baseline but only the LEI and Gladman indices showed a large effect size. All indices demonstrated a floor effect (a score of 0 when the MEI is >0) but this was minimal for the LEI index. All indices correlated strongly with each other and other measures of disease activity.


CONCLUSIONS
The LEI is a new enthesitis index designed for use in PsA. It shows good test characteristics that suggest it will be a robust and reliable assessment tool. We suggest that it be adopted for use in any randomized controlled trials and longitudinal observation cohorts involving patients with PsA.
Healy
Paul J
PJ
Wellington Regional Rheumatology Unit, Hutt Valley District Health Board, Lower Hutt, New Zealand. paul.healy@huttvalleydhb.org.nz
Helliwell
Philip S
PS
D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D015535:Arthritis, Psoriatic / Q000175:diagnosis* / Q000188:drug therapy / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000627:therapeutic use; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016896:Treatment Outcome
D018501:Antirheumatic Agents; D008727:Methotrexate