A comparison of platelet count and acute phase proteins in the measurement of disease activity in rheumatoid arthritis.

Platelet count (PC) was compared with standard acute phase reactants (ESR, plasma viscosity and C-reactive protein) and clinical measurements to assess its usefulness as a measure of disease activity in 165 patients with active rheumatoid arthritis. Although PC was elevated (greater than 400 X 10(9) 1(-1) in 45% of patients and was seen to fall under the influence of second-line drugs, it was considered to be unsuitable as an indication of disease activity since levels fall for reasons other than disease improvement.