Not everyone gets headache. 4% of sufferers have a normal ESR. Biopsy can show false negatives.
Constitutional symptoms (fever, sweats, weight loss/anorexia, fatigue) are common; but do consider other causes (infection, malignancy).
Visual symptoms can affect part of the visual field rather than all of it; check fields. It can cause scotomata or diplopia.
Ultrasound is often diagnostic, which can reduce the number of biopsies needed.
Aspirin has been shown to reduce risk of neurovascular complications.