Background RA activity is assessed by means of laboratory data and physical examination.
Objectives We assessed RA activity during the year in order to investigate whether the seasonal change influences parameters for the assessment of RA activity or not. This investigation may be useful to assess the reliability of parameters for RA activity.
Methods This study consisted of 348 patients (281 females and 67 males) with RA including 140 patients treated with biologics. The average age was 62.1 years old and the average period of RA was 10.8 years in all patients, and the average age was 63.0 years old and the average period of RA was 11.9 years in patients treated with biologics.
This study was performed in Fukuoka city, Japan. Fukuoka city locates in southern part of Japan and clearly has four seasons. Since September 1st 2009 to August 31st 2011, all parameters for RA activity were assessed in total 3811visits of 348 patients including 2174 visits of 140 patients treated with biologics. In the patients treated with the biologics, tocilizumab was administrated 437 times, etanercept 1171 times, abatacept 28 times, adalimumab 77 times and infliximab 461 times. The parameters were CRP, ESR, MMP-3, Rheumatoid factor, tender joints count, swollen joints count, patient general health measured on a visual analogue scale, DAS28-CRP and DAS28-ESR. All parameters in each month in the first year and the second year were assessed and the results were compared among the months. The monthly average temperature in Fukuoka city in 2 years since September to August was 25, 19, 13, 8, 4, 8, 9, 14, 19, 23, 27 and 29 degrees Celsius.
Results In all cases, the average CRP value was 0.65mg/dl since October to December and was 0.53mg/dl since July to September. The difference was statistically significant (p<0.05). In cases with biologics, the average CRP value was 0.67mg/dl since October to December and was 0.50mg/dl since January to March. The difference was statistically significant (p<0.05). The CRP value of 0.70mg/dl since April to June was also significantly higher than that since January to March (p<0.01). No significant difference was found in other parameters. However, ESR and MMP-3 values were also higher since October to December and since April to May. CRP was significantly higher in autumn to early winter and in spring even in the patients treated with biologics.
The results clearly showed that seasonal change significantly influenced the CRP values. In autumn, some patients may have cold or some kinds of respiratory infections and/or inflammation. In spring, pollinosis is widespread in Japan. These respiratory diseases may increase CRP value. However, MMP-3 value was also higher in autumn and spring even though no significant difference was found. In winter, CRP value was stable even though the temperature was the lowest in the year. The seasonal change may influence RA activity.
No significant difference was found in ESR values. It may be better to use ESR for the assessment of RA activity throughout the year. DAS28CRP was not influenced by the difference of CRP value. On the other hand, SDAI value may be influenced by the difference of CRP value to some extent because CRP value is simply added to CDAI value. When RA activity is assessed, it may be better to consider the change of seasons.
Conclusions Seasonal change significantly influenced the CRP values in RA patients.
Disclosure of Interest None Declared
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