Ultrasound examination of the temporal artery was proposed as a noninvasive assessment for GCA more than 15 years ago. Though earlier analyses expressed concerns about sensitivity and specificity, the technique has persisted, much more so in Europe than in the U.S. (another rheumatologic mystery), and recent studies continue to cite an adequate performance as a diagnostic test for GCA.9,10 Still, given the inescapable fact of its operator dependency, the diagnostic value of this procedure will continue to be controversial. A noninvasive, sensitive, and specific test for the diagnosis of GCA remains a major unmet need.
What about a strongly suspected diagnosis of GCA that cannot be confirmed by histopathology or other means? Most of us certainly treat such patients—though I find “biopsy-negative GCA” as among the most fraught of rheumatologic diagnoses. It might be noted that there is scant literature on these patients, and that most of the published studies on GCA—diagnosis, treatment, and clinical course—are largely composed of patients who are biopsy positive.
GCA: What’s Easy, What’s Not
What’s easy in GCA is its treatment, specifically, the prevention of blindness. Corticosteroids work. If there is no vision loss at the time that GCA is diagnosed, and if treatment is instituted with higher doses of CS, given daily, the risk of subsequent vision loss is very small, probably less than 1%.11 (If vision loss due to GCA has already occurred, a small percentage of patients may experience further deterioration of vision during the first week or two of treatment.) I am, of course, painting with a broad brush; there are manifold difficulties in the treatment of GCA, nearly all of which have to do with the toxicities of higher doses of CS. But the proven ability of the appropriate and timely administration of CS to prevent blindness in GCA is a yardstick against which any other treatment must be measured.
Could CS toxicities be lessened by using a lesser dose than the traditional 1 mg/kg? The dosing of CS for the treatment of GCA is based on retrospect and custom; there are no prospective studies. No doubt the specter of blindness drives the choice of high-dose CS. If patients could be stratified for the risk of blindness, perhaps the CS dose could be accordingly calibrated. No clinically reliable means for such stratification have emerged; probably the strongest risk factor for subsequent permanent loss of vision is a history of prior amaurosis. It is also worth bearing in mind that the majority of patients with GCA in fact do not incur the catastrophe of vision loss. Such was the case of the first reported GCA patient, one Mr. Rumbold, as vividly described by Hutchinson in 1890.12
