Association between mean platelet volume and severity of rheumatoid arthritis

Introduction In recent years, it is suggested that platelet histogram indices, such as mean platelet volume (MPV) may be related to the activity of rheumatoid arthritis (RA). The aim of this study was to assess relationship between MPV and activity of rheumatoid arthritis. Methods Sixty consecutive patients fulfilling the American College of Rheumatology (ACR) criteria for RA were recruited from the rheumatology outpatient clinics in Semnan, Iran. Current disease activity score (DAS-28 score) was assessed at baseline, 2 months and 4 months after the admission time and beginning of the treatment schedule. Complete blood count (including MPV), C-reactive protein (CRP) and ESR were measured in each visit. MPV was analyzed by the Cell Dyne 3500 automated blood cell counter. Results There was a significant reduction in DAS-28 score within 4 months of total assessment (from 4.47 ± 2.24 versus 3.18 ± 1.55) (p < 0.001). There was no significant difference in MPV levels at the three study time points. No significant correlations were observed between the DAS-28 score and mean MPV levels at the same time points. The rate of positive CRP was decreased within the same period (p = 0.002); however, the trend of the changes in other laboratory parameters including MPV, platelet count and ESR values was not significant. The measurement of MPV value did not correlate with disease activity in RA patients within 4 months of treatment scheduling. Conclusion Although therapeutic regimens, which improve RA manifestations, can reduce RA activity, they had no effect on MPV during this time period. It seems MPV may not be able to predict disease activity in RA patients.


Introduction
Currently, many physicians are interested in platelet indices, particularly the platelet volume, because it may reflect the platelet function better than the platelet count itself. Nowadays, platelet volume is usually reported in routine complete blood count results.
The mean platelet volume (MPV) reflects the platelet size. Elevation of MPV is a suggestive paraclinical indicator for platelet production and activation [1]. Several studies showed the role of platelet indices such as MPV in thrombosis, immunity, inflammation and angiogenesis [2,3]. In clinical settings, changes in this simple marker are linked to cardiovascular disease, brain stroke risk profile, dyslipidemia, hypertension, non-insulin dependent diabetes mellitus, overweight [4][5][6][7]. Disease-specific and cardiovascular confounding factors affect the direction of MPV changes. Platelet count estimations complicate the interpretation of MPV values in thrombocytopenia. It would seem that the size of circulating platelets is dependent on the intensity of systemic inflammation, with contrasting features of MPV in high and low-grade inflammatory disorders and the course of anti-inflammatory treatment [3]. Rheumatoid arthritis (RA) is a chronic inflammatory disease which characterized by tenderness, swelling and stiffness of the joints, with progressive destruction of cartilage and bone [8]. It has been recently identified that MPV is one of the most widely used surrogate markers of platelet function and has been shown to reflect inflammatory burden and disease activity in rheumatic arthritis. Thus, serial measurements of MPV may be worthwhile in prediction of developing of different diseases [9]. The aim of the current study was to assess relationship between the changes of MPV and indices of RA activity.

Results
Mean ± SD of age was 49.5 ± 12.3 years (ranged 25 to 74 years) and 51 (85.0%) were female. The Mean ± SD duration of disease was 6.2 ± 6.5 years that was statistically similar in men and women (7.8 ± 9.7 years versus 5.9 ± 5.8 years, p = 0.786). At baseline, Page number not for citation purposes 3 mean DAS-28 score was 4.47 ± 2.24. As showed in Table 1 and regarding changes in study parameters within 4 months of the assessment, significant difference was noted in the rate of disease activity that significantly reduced at 4-month time point. The trend of the changes in DAS-28 score was significant, so that it was significantly decreased from its baseline level of 4.47 ± 2.24 to 3.18 ± 1.55 over 4 months of total assessment ( Figure 1 and Table 1).
Comparing mean MPV values between the groups showed no significant difference in MPV levels at the three study time points.
No significant correlations were observed between the DAS-28 score and mean MPV levels at the same time points ( Table 2). The rate of positive CRP was decreased within the same period (p = 0.002); however, the trend of the changes in other laboratory parameters including PLT and ESR values was not significant (Table 1).

Discussion
In present study, regarding trend of the changes in RA severity,

Conclusion
Although therapeutic regimens, which improve RA manifestations, can reduce RA activity, they had no effect on MPV during this time period. It seems MPV may not be able to predict disease activity in

RA patients within 4 months of treatment scheduling
What is known about this topic  In recent years, it is suggested that Platelet histogram indices such as MPV may be linked to the activity of RA.

What this study adds
 MPV value may not be able to predict diseases activity in RA patients.