Results from a 5-year prospective study have identified baseline clinical features that can successfully differentiate polymyalgia rheumatica (PMR) from late onset rheumatoid arthritis (RA).
“At first presentation, there are many similarities between PMR and late-onset RA, which, in some cases, may lead to significant diagnostic difficulties,” say Colin Pease (Department of Rheumatology, Chapel Allerton Hospital, Leeds, UK) and colleagues.
To try to improve accuracy of diagnosis at first presentation, they studied 142 late-onset RA (rheumatic factor negative), 147 PMR, and 42 PMR plus temporal arteritis patients seen consecutively by one rheumatologist over a 10-year period.
All patients had clinical data collected at baseline and during at least 5 years of follow-up.
Pease and team found that, compared with late onset RA patients, those with PMR were younger, had more frequent myalgia (100% vs 16%), and less frequent arthritis in the proximal interphalangeal, metacarpophalangeal, and wrist joints.
They also commonly had increased levels of the HLA-DRB1 alleles *0101/0102 and *0401 compared with healthy controls. In contrast, late-onset RA patients only had increases in *0401.
A diagnostic algorithm was developed, showing that presence of plasma viscosity and arthritis in the wrist plus either the proximal interphalangeal or metacarpophalangeal joints at initial diagnosis is likely to indicate the presence of late-onset RA rather than PMR.
The researchers comment that “using clinical data available at presentation, it proved possible to accurately predict the final diagnosis obtained during long-term follow-up.”
They conclude: “It is hoped that this algorithm will aid the early diagnosis of RA in the over-60-years age group with the earlier initiation of appropriate second-line therapy.”
The results are published in the journal Rheumatology.
Hi Lynn
Could you post this on the polymyalgia site as I am sure there are many who would be interested.