Background Angiogenesis and vasodilatation play a crucial role in the development and perpetuationof synovitis in rheumatoid arthritis (RA). Ultrasonography (US) is an useful tool for evaluation of pannus vascularization in active RA. Differently from US power Doppler (pD), the resistive index (RI) of spectral Doppler provides a quantitative analysis of vascular inflammation. As the musculoskeletal structures are characterized by high-resistance flows, the RI has a value of 1 in normal conditions; a decrease in the RI is registered in case of inflammation.
Objectives To investigate a possible association of the RI spectral Doppler with other US parameters of synovitis and clinical measures of disease activity in established RA.
Methods 95 pD-positive RA patients (1987 ACR criteria) were consecutively evaluated and scanned in this prospective cross-sectional study. Disease acitivity and disability were measured using Disease Activity Score in 28 joints (DAS28) and Health Assessment Questionnaire (HAQ), respectively. US examination was performed by ultrasound-trained rheumatologists in 10 hand joints (the wrists, 2nd and 3rd metacarpophalangeal and 2nd and 3rd proximal interphalangeal joints) using high-resolution equipment (MyLab 60, Esaote). Clinical and US evaluations were performed in a blinded fashion. Gray-scale (GS) and pD were searched using a semi-quantitative scale (0–3). For each patient, the most inflammed joint on US examination was identified and, then, RI was measured at least on three different sites of the sinovial area. The sum of the individual joint scores for GS and pD (10-joint score GS or pD) and the mean RI of the most US-affected joint were calculated. Kappa statistics was used to evaluate interobserver reability. Mann-Whitney test and Spearman correlation coefficient (rS) were used for statistical analysis.
Results Patients' features were mean age, 55.6±11.8 years; female gender 79%, positive rheumatoid factor, 58%; median disease duration, 7 (range, 1–36) years; mean DAS28, 4.33±1.66; mean HAQ, 1.04±0.88. Real-time US interobserver kappa was 0.77 for GS, 0.87 for pD, and 0.68 for RI. RI was not significantly associated with 10-joint pD-score (rS=-0.15, 95% CI -0.33 to 0.05, p=0.15; figure 1), 10-joint GS-score (rS=-0.14, 95% CI -0.31 to 0.04, p=0.17), DAS28 (rS=0.05, 95% CI -0.17 to 0.26, p=0.61) or HAQ (rS=-0.01, 95% CI -0.22 to 0.20, p=0.95). There was also no association of RI with the presence of bone erosions (p=0.72).
Conclusions RI was not either clinically or statistically correlated with clinical measures of disease acitivity, US inflammatory parameters, and structural damage in our study. Adding the RI to musculoskeletal US evaluation does not seem to improve US performance in PD-positive patients with established, long standing RA.
Terslev L et al. 2008;35(1):49–53
Carotti M et al. Eur J Radiol. 2012;81(8):1834–8
Disclosure of Interest None declared