Background Power Doppler can show the degree of hyperemia in inflamed synovium. Serum inflammatory markers also reflect the arthritic activity in various rheumatic disease including rheumatoid arthritis. However, no report has been published regarding an association between them.
Objectives We investigated an association between power Doppler semiquantitative signal grade and all the 5 serum inflammatory markers of white blood cell (WBC), hemoglobin (Hb) and platelet (PLT) count which possibly can be used in the practical field as well as commonly used ESR and CRP.
Methods Rheumatic disease patients initially presenting with objective joint tenderness or swelling were evaluated with ultrasound and blood test was done to determine serum inflammatory marker level. A total of 827 ultrasound examined joints (112 metacarpophalangeal, 85 metatarsophalangeal, 82 proximal interphalangeal, 13 knee, 46 tendons, 136 ankle, 53 elbow, 15 hip, 255 wrist, 29 shoulder) from 2009 to 2014 were analyzed in this study. According to rheumatic disease classification, rheumatoid arthritis was most common and undifferentiated arthritis, ankylosing spondylitis and gout followed. ANOVA, two sample T-test, Spearman correlation test, multiple linear regression and logistic regression analysis were performed for statistics using SAS 9.2 version. p<0.05 were considered as significant.
Results The presence of positive Doppler signal itself was associated with elevated ESR, CRP and PLT number but not Hb level at the time of ultrasound examination (ESR, CRP: p<0.0001, WBC: p=0.0116, platelet: p=0.0246). Spearman correlation coefficients showed positive linear association between power Doppler grade and serum levels inflammatory markers (ESR: r=0.21, CRP: r=0.30, WBC: r =0.13, platelet: 0.11, p-value <0.05) except Hb level. However, multiple linear regression test after adjusting confounding variables showed that only the CRP level among the 5 variables showed a positive relationship with power Doppler grade (p=0.0022). Furthermore, logistic regression test showed one step increase of Doppler grade resulted in 1.3 mg/dL increase of serum CRP level. Post hoc (Scheffe) analysis showed rheumatoid arthritis was the most correlated disease among the rheumatic diseases we included.
Conclusions In a patient with presenting objective joint tenderness or swelling, if there is a positive power Doppler signal, it is associated with elevated serum markers of inflammation. Especially, the CRP is the only marker that have positive correlation with the Doppler signal semi-quantitative grade. One grade up of Power Doppler signal is expected to elevate CRP as amount of 1.3 mg/dL. Rheumatoid arthritis is the most associated disease that can be applied this result.
Disclosure of Interest None declared