To determine whether the low absolute numbers and percentages of CD8 positive T cells in the circulation of patients with polymyalgia rheumatica (PMR) could be used as a new diagnostic criterion for the disease.
The % CD4 and CD8 positive T lymphocyte sub-populations were measured in 37 patients with PRM before treatment and during steroid treatment over the subsequent 2 years, in 21 patients with rheumatoid arthritis (RA), and in 27 normal (N) control subjects.
During the study, 10 patients, who were initially diagnosed as PMR, were reclassified as having had a myalgic onset of RA (PMR-RA), according to the American College of Rheumatology criteria for the diagnosis of RA. No decreased %CD8+ T lymphocyte subset had been observed in these patients at presentation, before steroid therapy, or during treatment with steroids when compared with the RA and N groups.
The measurement of %CD8+ T cell subset may provide a simple method for determining whether patients presenting with myalgia are "true" PMR or are destined to develop RA.