OP12. DISEASE ACTIVITY ASSESSMENT IN POLYMYALGIA RHEUMATICA (PMR) AND GIANT CELL ARTERITIS (GCA)

Abstract

Polymyalgia rheumatica (PMR) constitutes a common rheumatic disorder in the elderly population, affecting from 0.1 to 0.5% of people older than 50 years. The diagnosis is based upon a clinical syndrome, consisting of pain and stiffness in the shoulder and pelvic girdle, muscle tenderness of the upper and lower limbs, non-specific somatic complaints, frequently occurring fever, weight loss and fatigue. Moreover the acute phase response measured by Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) is highly elevated, despite the fact that PMR may also exist without elevated acute phase reactants [1–3]. Although PMR and Giant Cell Arteritis (GCA) are commonly regarded as two clinical variations of the same disease, their clinical picture is quite different. Whilst in PMR the musculoskeletal symptoms predominate, arterial inflammation and its consequences constitute the major features of GCA [1]. Giant-cell arteritis is less frequent than polymyalgia rheumatica. The American College of Rheumatology-criteria include an erythrocyte sedimentation rate of at least 50 mm per hour as one of the five criteria found to be useful in the classification of giant-cell arteritis [4]. It is well known and overall consensus that corticosteroid therapy in PMR and GCA usually leads to a rapid and dramatic improvement. Usually higher starting doses are administered in GCA patients. [1]. The EULAR response criteria for PMR and the PMR-disease activity score (PMR-AS) [5, 6] were developed on the basis of corticosteroid treatment. Along with the reduction of corticosteroids almost all parameters of disease activity, showed significant improvement indicating decrease of inflammatory activity, reduction of pain, and amelioration of functional status of the patients. The EULAR response criteria for PMR comprise a core set of markers of disease activity for monitoring therapeutic responses in PMR, namely ESR or CRP, representing the acute phase response, and the VAS of patient's pain, Physician's global assessment (PhGA), morning stiffness (MST) and the ability to elevate the upper limbs, representing the clinical situation [5]. In view of the crucial role pain plays during the course of the disease, it was decided to insist on the presence of a change of pain intensity, whereas out of the other four parameters only three have to change to indicate improvement or deterioration [5]. In order to express PMR-activity as an absolute number a PMR disease activity score, the PMR-AS, was developed on the basis of the EULAR response criteria. The PMR-AS is to be calculated as: CRP (mg/dl) + VAS p (0 – 10) + VAS ph (0 – 10) + [MST (min)*0,1] + EUL (3 – 0) [6]. Cronbach's alpha for the composite score amounted to 0.914 and 0.881 in two patient cohorts, indicating high internal consistency. Factor analysis revealed that each single item contributes significantly to the total score. PMR-AS values below 7 can be regarded as indicating low disease activity, between 7 and 17 medium disease activity, and greater than 17 high PMR-activity. In a third control cohort the PMR-AS was proven to be highly correlated to patient's global assessment, patient satisfaction and ESR (p<0.001) [6]. In GCA the onset of symptoms may occur subacutely, but also abruptly. An elevated ESR as well as elevated CRP-levels and elevated Interleukin-6-levels (IL-6) are considered as diagnostic features and as markers for disease activity [1]. Imaging techniques, such as magnetic resonance imaging and PET-scans play an important role as diagnostic, but also as monitoring tools during the course of GCA and its treatment respectively [7, 8]. Up to now the gold standard of monitoring GCA- patients comprises ESR or CRP, which is thought to provide higher specificity, in addition the control of symptoms as well as patient's global assessment. Anticardiolipin antibody levels may be helpful to predict flares and relapses in GCA patients; additionally IL-6 levels were recently described not only as markers for disease activity assessment, but also as prognostic markers. An elevated Il-6 production was seen to be related to a lower incidence of disease related ischemic events in GCA-patients [9, 10]. It may be anticipated that a better knowledge of disease activity processes, an exact monitoring of disease activity and treatment responses, as well as an increased risk-estimation of treatment schedules, e.g. corticosteroids, in PMR and GCA will result in improved clinical decision–making and ultimately in improved patient care.