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The impact of disease extent and severity detected by quantitative ultrasound analysis in the diagnosis and outcome of giant cell arteritis.

OBJECTIVES
To develop a quantitative score based on colour duplex sonography (CDS) to predict the diagnosis and outcome of GCA.


METHODS
We selected patients with positive CDS and confirmed diagnosis of GCA recruited into the TA Biopsy (TAB) vs Ultrasound in Diagnosis of GCA (TABUL) study and in a validation, independent cohort. We fitted four CDS models including combinations of the following: number and distribution of halos at the TA branches, average and maximum intima-media thickness of TA and axillary arteries. We fitted four clinical/laboratory models. The combined CDS and clinical models were used to develop a score to predict risk of positive TAB and clinical outcome at 6 months.


RESULTS
We included 135 GCA patients from TABUL (female: 68%, age 73 (8) years) and 72 patients from the independent cohort (female: 46%, age 75 (7) years). The best-fitting CDS model for TAB used maximum intima-media thickness size and bilaterality of TA and axillary arteries' halos. The best-fitting clinical model included raised inflammatory markers, PMR, headache and ischaemic symptoms. By combining CDS and clinical models we derived a score to compute the probability of a positive TAB. Model discrimination was fair (area under the receiver operating characteristic curve 0.77, 95% CI: 0.68, 0.84). No significant association was found for prediction of clinical outcome at 6 months.


CONCLUSION
A quantitative analysis of CDS and clinical characteristics is useful to identify patients with a positive biopsy, supporting the use of CDS as a surrogate tool to replace TAB. No predictive role was found for worse prognosis.