Giant cell arteritis (GCA) is a nasty inflammatory disorder that affects the large arteries. Because it characteristically involves the temporal artery, this form of vasculitis is also referred to as temporal arteritis. It usually affects people over the age of 50 years and manifests with sudden onset headache, scalp pain, and a thick, tender temporal artery. GCA is often accompanied by polymyalgia rheumatica (PMR) , a painful condition of the joints and muscles. The active systemic inflammation in GCA is often detected by the erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) tests. These distinguishing features constitute most of the diagnostic criteria for GCA.
Most people with GCA however do not have all the ‘classical’ features of the disease. A high index of suspicion is therefore required to sniff out the duplicitous miscreant. It is particularly imperative to make the diagnosis as early as possible to prevent the dreaded complications of GCA, sudden blindness and stroke. The treatment of GCA, implemented according to established treatment guidelines, involves several months of oral steroids, drugs which cause immune suppression and a host of other side effects. It is therefore essential that the diagnosis of GCA is made correctly to avoid putting the patient on a long, risky, and unnecessary treatment.
The conventional method of establishing the definitive diagnosis of GCA is by performing a temporal artery biopsy. This involves taking a short segment of the temporal artery as it traverses the temple. This procedure however only confirms the diagnosis of GCA in 13–35% of people with the condition. One reason the biopsy has such a poor sensitivity is that it is often performed after treatment has already commenced. Another reason the biopsy is often normal is that the inflammation in GCA occurs in patches, sparing large segments of the artery. Don’t even think about it-taking a longer biopsy segment does not increase the yield of temporal artery biopsy. Put another way, “specimen length is not associated with diagnostic yield of temporal artery biopsy“.
This is an entirely reasonable question especially because there are other more accurate and less invasive ways of establishing the diagnosis of GCA. These include: