Classification Criteria for Polymyalgia Rheumatica
With no single test, no single symptom, and no known specific biomarkers, PMR has been difficult to diagnose and is often confused with other diseases. Those factors have also complicated research efforts. “It presents a problem if you try to formally study polymyalgia rheumatica because you need to be able to classify it and have confidence that the patient you have in your study actually has the disease,” Dr. Matteson says. The lack of standardized criteria has contributed to problems in assessing potentially effective therapies, he says.
The new “Provisional Classification Criteria for Polymyalgia Rheumatica” are addressing that problem.4 Not intended nor tested for diagnostic use, the criteria are intended, instead, to inform research efforts so that patients identified with these criteria are grouped together for the purpose of studying the disease course and treatments, Dr. Matteson says. “We hope in the future to [identify] a more specific biomarker or biomarkers so that we can say that if you have this biomarker or group of biomarkers and these symptoms, we are certain you have polymyalgia rheumatica and not some other disease that can be confused with it.”
Development of the PMR classification criteria was based on an international multicenter prospective study that examined consensus-based criteria proposed by a group of experts that included 111 rheumatologists and 53 nonrheumatologists in the United States and Western Europe. For the study, patients with new onset PMR were followed for a minimum of six months while receiving a standardized corticosteroid treatment regimen.
This group was compared with another group of patients who had new onset bilateral shoulder problems due to another condition. At the end of follow-up, the researchers determined which features were the most helpful in determining which patients had PMR.
The features identified for PMR classification were:
- Patient aged ≥50 years presenting with bilateral shoulder pain;
- Elevated C-reactive protein and/or erythrocyte sedimentation rate in the presence of morning stiffness >45 minutes;
- New hip pain in the absence of peripheral synovitis or positive rheumatoid arthritis serology; and
- Ultrasound score ≥5.
Noticeably absent from these criteria was response to low doses of corticosteroids, long believed to be a feature of PMR but found to have little validity in this study. “Many inflammatory rheumatic conditions such as rheumatoid arthritis are improved with corticosteroid therapy, so this response does not help in disease classification,” Dr. Matteson says. “An important aspect of dropping the response to corticosteroids is that it also facilitates enrollment of patients with PMR into studies evaluating the utility of various treatments compared with corticosteroids.