I went to the emergency room after losing vision in one eye for a few seconds. While I was there they ran a LOT of tests, checking for stroke and other problems. Also while I was there I had more episodes of losing vision temporarily. I think the temporary vision loss and relatively high values for the sedimentation rate (ESR) and C-Reactive Protein tests were the main indicators, plus the other symptoms I had like jaw muscle fatigue, low grade fever for several weeks, and scalp tenderness. They immediately started giving me IV infusions of high dose prednisone, and they did a temporal artery biopsy less than 24 hours after I went to the hospital. That came back positive for GCA.