Background: Systemic signs of inflammation such as raised CRP or ESR are a classical feature of PMR, but some patients present with normal acute phase reactants (APR). ^1,2 It is not known whether these patients represent milder forms of PMR, whether their disease is not yet fully expressed, or whether they represent another pathophysiological subset of PMR or another disease. Data on demographic and clinical differences between PMR patients with normal versus elevated APR might provide some answers.

Objectives: To explore baseline differences in demographics and clinical characteristics in PMR patients with and without elevated APR.

Methods: We conducted a retrospective cohort study of clinical characteristics of newly diagnosed PMR patients (clinical diagnosis) who visited our outpatient clinic between April 2012 and September 2017. Patient with concomitant inflammatory rheumatic disease were excluded. Data on patient-, disease,- and treatment characteristics were extracted from the electronic health record. Descriptive statistics were used [using mean (SD), median (p25-p75) or n (%) as appropriate], and differences between patients with high APR(CRP>10 mg/L and/or ESR >30mm/hour) were tested using Fischer’s exact test for categorical data, t-test for normally and Wilcoxon test for non-normally distributed data.

Results: 454 patients were included (table 1). Sixty-two patients had normal, and 392 had elevated APR. In the group with normal APR, fewer patients had peripheral arthritis (2 versus 9%; p=0.044) and fewer had anemia at diagnosis (17 versus 43%; p= 0.001). Furthermore, patients had a longer median duration of symptoms before diagnosis (13 versus 10 weeks; p= 0.0196) and were more likely to have a history of PMR (16 versus 8%; p= 0.057). No significant differences were found in other clinical characteristics.

Conclusion: The results of this cohort indeed suggest that patients with normal APR are a different subset of PMR patients. Fewer cases have peripheral arthritis and anemia at diagnosis, suggesting a milder form of PMR. Secondly, our results do not support the hypothesis that PMR of those with normal APR is not yet fully expressed, as they have a longer symptom duration prior to diagnosis.

REFERENCES:

[1] Buttgereit F, Dejaco C, Matteson EL, Dasgupta B. Polymyalgia Rheumatica and Giant Cell Arteritis: A Systematic Review. JAMA. 2016 Jun;315:2442-58.

[2] González-Gay MA1, Matteson EL2 Castaneda S3. Polymyalgia rheumatica. Lancet. 2017 Oct Oct 7;390(10103):1700-1712

Disclosure of Interests: None declared

DOI: 10.1136/annrheumdis-2019-eular.5685