Patients with polymyalgia rheumatica (PMR) with normal acute phase reactants (APRs) represent a distinct subset of individuals with milder disease presentation, prognosis, and possibly a different pathophysiologic pathway from that observed in the same spectrum of disease, according to study results published in Clinical and Experimental Rheumatology.
Researchers sought to examine whether patients with PMR who presented with normal APRs were caused by the fact that they were “caught early in the disease;” a misdiagnosis; or a distinct subset of PMR with varying clinical presentation and disease prognosis.
A retrospective explorative cohort study was conducted among patients with a clinical diagnosis of PMR who visited the outpatient rheumatology clinic of the Sint Maartenskliniek in Nijmegen, The Netherlands, between April 2008 and September 2017. All patients with a new clinical diagnosis of PMR or those with a new episode of PMR and had a follow-up of at least 9 months (minimum duration of glucocorticoid treatments) were eligible for study inclusion. Laboratory values of erythrocyte sedimentation rate and/or C-reactive protein levels were obtained — both of which are important markers for the diagnosis and assessment of PMR.
A total of 880 patients with PMR visited the Sint Maartenskliniek clinic during the 10-year study period. Overall, 454 (52%) of these individuals were included in the current analysis, among whom 62 (14%) had normal APRs and 392 (86%) had elevated APRs. Patients with normal vs elevated APRs had a significantly longer median duration of symptoms before diagnosis (13 vs 10 weeks, respectively; P =.02); however, 31% developed elevated APRs during follow-up. Patients with normal APRs vs those with elevated APRs were also significantly more likely to have a previous diagnosis of PMR (16% vs 8% respectively; P =.06).
Among the 392 patients with elevated APRs who had previously available APR data while they were symptomatic, 110 (58%) had no previous elevated normal APRs while having PMR symptoms. In addition, significantly fewer participants with normal vs elevated APRs had peripheral arthritis (2% vs 9%, respectively; P =.04) and anemia (17% vs 43%, respectively; P =.001) at diagnosis. Further, patients with normal APRs compared with those with elevated APRs had a previous PMR diagnosis (16% vs 8%, respectively; P =.057) and a shorter median time to glucocorticoid-free remission (552 vs 693 days, respectively; P =.02).
Researchers reported no differences in the 2 groups in distal swelling and pitting edema, systemic symptoms, osteoarthritis, the presence of rheumatoid factor or anti-citrullinated C-peptide, diabetes, and cardiovascular disease.
Limitations included the study’s retrospective design, index date event bias, and the lack of generalizability to all patients with PMR.
Researchers concluded that although diagnosing PMR in patients with normal APR values remains a challenge, as shown with delayed diagnosis and the lack of a gold standard diagnostic test for the disease, clinicians can diagnose PMR when APRs are normal.
Marsman DE, den Broeder N, Boers N, et al. Polymyalgia rheumatica patients with and without elevated baseline acute phase reactants: distinct subgroups of polymyalgia rheumatic? Clin Exp Rheumatol. 2021;39(1):32-37.