Purpose: To evaluate the diagnostic yield and concordance of color duplex ultrasound (CDU) of the superficial temporal artery (STA), temporal artery biopsy (TAB), and American College of Rheumatology (ACR) criteria in the diagnosis of giant cell arteritis (GCA).
Methods: Prospective, masked study of all patients evaluated in one institution suspected of having GCA. All patients with a suspected diagnosis of GCA were admitted for pulsed intravenous corticosteroids. Patients underwent serologic work-up and ACR criteria were documented. All patients had a CDU and TAB performed within 3 days of initiation of systemic corticosteroid therapy. Main outcome measure: Concordance of CDU and TAB. Secondary outcome measures: Concordance between unilateral and bilateral CDU and TAB by side and segment, concordance between TAB and ACR criteria, and statistical analysis of serologic markers for GCA.
Results: The diagnosis of biopsy-proven GCA was found in 14 of 71 (19.7%) patients. The sensitivity of CDU compared to the reference standard of TAB ranged between 5.1% and 30.8% depending on the signs studied on CDU and correlation of specific TAB parameters. Of the serologic studies, a platelet count threshold of 400,000μL had the highest positive (18.32) and lowest negative (0.37) likelihood ratios for a diagnosis of GCA.
Conclusions: In this study, CDU showed minimal value in diagnosing GCA compared to TAB. There was poor correlation between CDU results and ACR criteria for GCA. The threshold platelet count had higher positive and negative predictive values for GCA than CDU and is a useful serologic marker for GCA.