Dr Elisa Fernández-Fernández presented a study looking at the validity of existing EULAR recommendations on the use of ultrasound in the diagnosis of GCA – specifically colour doppler ultrasound (CDUS). The results show that combining the results of a pre-test probability score with the CDUS allows for an accurate diagnosis of GCA, as established by the EULAR group, with less than 2% misclassification. Even a negative CDUS in patients with intermediate risk showed strong association with a negative diagnosis. This study validates the EULAR recommendations for the use of imaging in large vessel vasculitis, and establish that an imaging test supported by clinical pre-test probability is sufficient for the diagnosis of GCA.
Three other groups presented data at the congress on the evidence for ultrasound in GCA.
The ultrasonographic Halo score provides a quantitative measure of the extent of vascular inflammation in GCA. High Halo scores correlate with systemic markers of inflammation and may help diagnose GCA with high specificity. However, an increase in intima media thickness (IMT) in patients with elevated cardiovascular risk may lead to false positives. Dr Juan Molina Collada presented findings from a retrospective observational study in 157 patients referred to a fasttrack ultrasound clinic.
There were no differences in cardiovascular risk between patients with and without GCA. Among patients without GCA, extra-cranial artery IMT and Halo scores were significantly higher in those with high or very high risk than in those with low or moderate risk. The group conclude that high cardiovascular risk may influence the diagnostic accuracy of the ultrasound Halo Score, leading to false-positive findings in these patients. This suggests that cardiovascular risk should be considered in the vascular assessment of patients with suspected GCA.
Follow-up assessment of Halo count and different quantitative scores based on intima media complex (IMC) measurement of Halos have demonstrated potential to show sensitivity to change. Including IMC of normalized arteries in such scores may reduce the risk of missing new arteritic lesions and assessment bias towards a response. Berit Dalsgaard Nielsen and colleagues aimed to evaluate ultrasound scores based on Halo features and scores based on IMT measurements of both visually normal and arteritic arteries in a prospective cohort of 47 new-onset patients.
All ultrasound outcomes improved during follow-up and were apparent by week 8. However, only scores including temporal arteries consistently showed statistically significant change from baseline, and a significant correlation with markers of disease activity. Some scores based on large vessels showed a weak correlation with C-reactive protein, but otherwise did not correlate with clinical disease activity. These findings confirm ultrasound as a potential tool for monitoring treatment response in people with GCA.
Polymyalgia rheumatica (PMR) and GCA are closely related, with PMR occurring in approximately 50% of patients with GCA. Research presented by Dr Eugenio de Miguel aimed to determine the prevalence of subclinical GCA in 258 people with newly diagnosed PMR, using vascular ultrasound as a diagnostic tool.
The results showed that one-fifth of PMR patients without symptoms or signs of GCA have ultrasound findings consistent with the diagnosis of GCA. Overall, 24.3% had only temporal artery involvement (cranial GCA), 65.8% had an extra-cranial artery involvement, and 9.8% had a mixed form.