To determine laboratory parameters that may be useful in identifying polymyalgia rheumatica (PMR) patients who require long-term corticosteroid therapy.
A prospective followup study of 94 consecutive untreated patients with PMR were assessed for relapse/recurrence for a mean of 39 months. This cohort represented all the patients diagnosed over a 4-year period in 2 Italian secondary referral centers. Patients were monitored for clinical signs and symptoms, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and serum interleukin-6 (IL-6). IL-6 levels were also measured in 43 controls matched to the patients for age and sex.
The ESR was elevated in 91.5% of the patients prior to therapy initiation, as were CRP in 98.9% and serum IL-6 in 92.6%. Forty-seven (50.0%) patients had at least 1 relapse/recurrence during the followup period and 24 (25.5%) had at least 2. After 4 weeks of prednisone therapy, ESR was elevated in 13.2% patients, CRP in 41.9%, and serum IL-6 in 37.2%. IL-6 levels remained persistently elevated in 9.9% and CRP in 8.7% of patients during the first year of followup, whereas no patient had persistently elevated ESR. Persistently elevated CRP and IL-6 levels were significantly associated with an increased risk of relapse/recurrence. In particular, patients with persistently elevated levels of IL-6 during the first year of therapy had the highest relative risk.
Despite the control of clinical symptoms, corticosteroids do not adequately control the inflammatory process in a subset of patients with PMR who have persistently elevated levels of CRP and IL-6 and who have a higher risk of relapsing.