Healy PJ and Helliwell PS (2008) Measuring clinical enthesitis in psoriatic arthritis: assessment of existing measures and development of an instrument specific to psoriatic arthritis. Arthritis Rheum 59: 686–691

Enthesitis is thought to underlie most manifestations of psoriatic arthritis. While there are several tools that assess enthesitis in ankylosing spondylitis, development of a validated measure that is specific to psoriatic arthritis has received little research attention. Healy and Helliwell evaluated the currently available tools, and developed a new instrument—the Leeds Enthesitis Index (LEI)—for use in patients with psoriatic arthritis.

This open-label, observational trial included 28 patients (mean age 46.5 years) with active psoriatic arthritis who started treatment with methotrexate (n = 19), leflunomide (n = 4), etanercept (n = 4) or hydroxychloroquine (n = 1). Patients were assessed 2 weeks, 1 month, 3 months and 6 months after initiation of treatment, with the following evaluations: Mander Enthesitis Index (MEI), Maastricht Ankylosing Spondylitis Enthesitis Score, Gladman Index, Psoriasis Area and Severity Index, 78-joint count and the Health Assessment Questionnaire.

The LEI was developed by applying an iterative data-reduction process to MEI scores. The LEI includes six examination points (left and right lateral epicondyles, medial femoral condyles and Achilles tendon insertions). All enthesitis indices correlated strongly with each other and with measures of disease activity, and all showed a floor effect (i.e. a score of 0 when the MEI >0), although this effect was minimal for the LEI.

The LEI seems to be a robust and reliable tool for assessing enthesitis in patients with psoriatic arthritis; the authors suggest that it should be used in future clinical trials.