Accuracy of power Doppler ultrasonography in the diagnosis and monitoring of idiopathic inflammatory myopathies

Abstract

Background No clear-cut guidelines exist about the use of imaging procedures for the diagnosis of idiopathic inflammatory myopathies (IIM). The aim of the present study was to assess the diagnostic accuracy of Power Doppler Ultrasonography (PDUS) score in IIM patients compared with a control group and its usefulness during follow-up. Methods All patients evaluated in the Vasculitis and Myositis clinic, Rheumatology Unit, University of Siena were prospectively collected. All patients underwent US examination of both thighs in axial and longitudinal scans, also performed twice(T1) or three times(T2). Results Forty-five patients with IIM (median age(IQR) 55(45–66) years; 35 female) were enrolled. ROC curve distinguished patients and controls based on ∑PD, ∑oedema, ∑atrophy and CRP. The best cut-off value for ∑PD was 0.5, ∑oedema 1.5, ∑atrophy 0.5 and CRP 0.22 mg/dl. In the logistic regression analysis, the variables that most influenced diagnosis of IIM were ∑PD and ∑oedema (p= 0.017 and p= 0.013, respectively). ∑oedema was lower at T1 (p= 0.0108) and T2 (p= 0.0012) than at T0. Likewise, ∑PD was lower at T1 (p= 0.0294) and T2 (p= 0.0420) than at T0. PhGA was lower at T1 (p= 0.0349) and T2 (p= 0.0035) than at baseline. Conclusion Our findings show that PDUS is a reliable diagnostic tool in the differential diagnosis between inflammatory and non-inflammatory myopathies. Moreover, PDUS can be employed also during the follow-up of patients with IIM. A reduction in disease activity, measured by PhGA, led to a concomitant decrease in both oedema and PD, which was directly correlated with their rate of change. This underlines the close link between clinical assessment and PDUS findings, not only at diagnosis but also during monitoring.