Unexplained shoulder pain and abnormal ultrasound findings of those large joints are part of provisional criteria published on polymyalgia rheumatica.
To be diagnosed with polymyalgia rheumatica (PMR) under the criteria proposed jointly by the American College of Rheumatology and the European League Against Rheumatism, patients should be at least 50 years old, have morning stiffness lasting at least 45 minutes, new hip pain, and elevated C-reactive protein and/or erythrocyte sedimentation rate.
ACR and EULAR based their criteria on findings from a prospective, international, multicenter cohort study, are published in the April issue of Arthritis & Rheumatism.
Additional validation in an external data set is required, and the criteria should not be used for diagnostic purposes, but they do have value for identifying the most appropriate patients for enrollment in clinical trials, and thus could pave the way for new therapeutic approaches and novel treatments for the inflammatory disease, Dr. Bhaskar Dasgupta of Southend University Hospital, Westcliff-on-Sea, U.K. and his colleagues reported (Arthritis Rheum. 2012 April;64:943-54).
PMR is a common condition, but its clinical management varies widely, due largely to considerable uncertainty with respect to diagnosis, disease course, and management, according to Dr. Eric L. Matteson, the study’s senior author, who noted in an interview that a lack of classification criteria has hampered development of rational therapeutic approaches because of difficulties in grouping together appropriate patients for enrollment in clinical studies.
"We have no good, established, and in any way validated criteria for classifying patients with having PMR. All previous criteria were based mainly on expert opinion, so what we did here was look at expert opinion about components of the disease that would help us classify a patient as having PMR, then tested to see which of the features in patients who appear to have PMR by expert diagnosis at the outset were most effective in identifying, for classification purposes, patients as having PMR after they were followed for 6 months," said Dr. Matteson, chair of rheumatology at the Mayo Clinic in Rochester, Minn.
The criteria were based on the findings of a criteria development work group convened in 2005 in response to an ACR/EULAR initiative. The group performed a systematic literature review, and through a multiphase process, identified candidate classification criteria, which were ultimately investigated in the 6-month prospective cohort study of 125 patients with new-onset PMR and 169 comparison patients with conditions mimicking PMR.
A scoring algorithm was developed based on four criteria: morning stiffness for greater than 45 minutes (2 points); hip pain/limited range of motion (1 point), absence of rheumatoid factor (RF) and/or anticitrullinated protein antibody (2 points), and absence of peripheral joint pain (1 point).
"A score of 4 or higher had 68% sensitivity and 78% specificity for discriminating all comparison subjects from PMR. The specificity was higher (88%) for discriminating shoulder conditions from PMR and lower (65%) for discriminating RA from PMR. The C statistic for the scoring algorithm was 81%," the investigators said.
The absence of peripheral synovitis or positive RF serology increased the likelihood of PMR.
Additionally, ultrasound was found to significantly improve the specificity of the clinical criteria, improving the C statistic to 82% when added to the scoring algorithm.
"Patients with PMR were more likely to have abnormal ultrasound findings in the shoulder (particularly subdeltoid bursitis and biceps tenosynovitis), and somewhat more likely to have abnormal findings in the hips than [do] comparison subjects as a group," the investigators said, adding that PMR could not be distinguished from RA on the basis of ultrasound, but could be distinguished from non-RA shoulder conditions and subjects without shoulder conditions.
Adding ultrasound to the scoring algorithm improved the C statistic of 82%.
The ultrasound finding mark the first time this technology has been systematically utilized in a longitudinal study for this purpose, Dr. Matteson said, adding that there are, indeed, typical findings on ultrasound in PMR, and although ultrasound alone can’t be used to identify PMR as opposed to RA, the findings can be helpful for classification of patients with PMR.
He also noted that the ultrasound features seen in PMR at the outset improved with treatment.
Patients and controls in the study were recruited from 21 community-based and academic rheumatology clinics in 10 European countries and the United States. All were aged 50 years or older, had new-onset bilateral shoulder pain, and no corticosteroid treatment within 12 weeks before the study. Patients had received a diagnosis of PMR, and corticosteroid treatment was initiated after enrollment.
The non-PMR comparison cohort included subjects with a variety of conditions that need to be distinguished from PMR, in both primary and secondary care, the investigators said.