Clinical and Genetic Factors at Onset of Polymyalgia Rheumatica Predict Prognosis
NEW YORK (Reuters Health) Feb 26 - At the onset of polymyalgia rheumatica, certain clinical and genetic factors increase the risk of poor outcomes, a recent prospective study has shown.
Specifically, increased plasma viscosity, female sex, certain HLA alleles, and a higher initial dose of steroids are associated with a worse prognosis, the research team reports in the January 11th online issue of Rheumatology.
Using data collected in a prospective cohort study, Dr. Sarah L. Mackie from the University of Leeds, UK, and colleagues analyzed the duration of steroid treatment, relapses, and development of giant cell arteritis in 176 patients with polymyalgia rheumatica.
After 5 years of follow-up, 124 of the patients had stopped taking steroids. A high initial steroid dose (> 15 mg) independently reduced the chances of stopping steroids by 7%. Also, compared to patients in the lowest tertile of plasma viscosity, odds of being able to discontinue steroids were 27% lower for patients in the middle tertile, and 51% lower for those in the upper tertile.
Seven patients died during the study, but none of the deaths were attributable primarily to polymyalgia or giant cell arteritis.
Eighty-three of 169 patients (49.1%) relapsed at least once during the 5-year follow-up, but none of the variables predicted relapse or the number of relapses.
Eighteen of 176 patients developed late giant cell arteritis at a median of 14.9 months after the start of treatment. Female gender, HLA-DRB1*0101 and HLA-DRB1*0401, higher plasma viscosity, and higher initial prednisolone dose were independently associated with an increased risk for late development of giant cell arteritis.
According to the article, the combination of baseline plasma viscosity of at least 2.0 millipascal seconds and one of the two genetic markers had a positive predictive value of 22% and a negative predictive value of 92% for giant cell arteritis.
As for the starting dose of steroids, the investigators said, "It seems likely that starting at greater than 15 mg prednisolone, for a given level of baseline inflammation, may prolong the steroid therapy. Developing giant cell arteritis following initiation of steroid therapy further prolongs steroid therapy, but this appears to be an independent effect."
"We were surprised by the apparently strong predictive power of the starting dose of steroids, particularly as this was independent of the level of inflammatory markers," they added.
"This provides further evidence to support current management guidelines," the researchers conclude.
Rheumatology 2010.