Background The platelet count, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR) are markers that reflect the inflammatory response in patients with rheumatoid arthritis (RA) (1). Although neutrophils, mast cells, and B and T lymphocytes have established roles in the pathogenesis of RA, the role of platelets is unclear (2).
Objectives The aim of this study was to investigate the correlation between the mean platelet volume (MPV) and inflammatory markers in patients with RA.
Methods The study was designed in the Sakarya University Faculty of Medicine Department of Rheumatology. A total of 102 patients with RA were retrospectively enrolled in the study. We used the DAS 28 to evaluate disease activity. The following clinical data were recorded: time elapsed from first clinical symptoms, time elapsed after diagnosis, presence of regular medication, and presence of clinical remission. Laboratory assessments included the complete blood cell count, ESR, CRP level, and MPV. Exclusion criteria included hematological, cardiovascular, and metabolic disorders that can affect assessment of the MPV.
Correlations among variables were assessed with Pearson's correlation test using SPSS 20.0. The Kruskal–Wallis test was used to compare MPV values and other laboratory parameters. A p value of <0.05 was considered to indicate a significant difference.
Results The patients' mean DAS 28 score was 3.14±0.57. A total of 16.8% of patients had high disease activity. There was a weakly positive correlation between DAS 28 scores and the disease-modifying antirheumatic drug count (p=0.002, r =0.336). There was a moderately positive correlation between DAS 28 scores and the ESR and CRP count (p=0.000, r =0.603 and p=0.000, r =0.640, respectively). There was a weakly positive correlation between DAS 28 scores and platelet counts (p=0.000, r =0.403). We found no correlation between CRP levels and MPV values (p<0.05, r = -0.098); on the other hand, there was a statistically significant correlation between DAS 28 scores and MPV in patients with RA (p<0.002, r = -0.316). MPV values were significantly lower in patients with high disease activity.
Conclusions In conclusion, MPV values were associated with disease activity in patients with RA. Thus, MPV may be used as a negative acute phase reactant in RA exacerbation. Measurement of changes in MPV values during follow-up may be a reliable tool in the assessment of the inflammatory response in patients with RA. We consider that evaluation of MPV values and platelet indices in patients with RA and other inflammatory diseases is useful. Platelet-derived microparticles may also be helpful to illuminate the relationship between MPV and clinical disease activity.
Choy EH, Panayi GS. Cytokine pathways and joint inflammation in rheumatoid arthritis. N Engl J Med 2001; 344: 907–916.
Smeets TJ, Dolhain RJ, Breedveld FC, Tak PP. Analysis of the cellular infiltrates and expression of cytokines in synovial tissue from patients with rheumatoid arthritis and reactive arthritis. J Pathol 1998 Sep; 186(1): 75-81.
Disclosure of Interest None declared