Abstract and Introduction
Early diagnosis and treatment of GCA is essential to prevent complications of the disease, including permanent vision loss. Temporal artery biopsy has been intrinsically linked with the diagnosis of GCA for several decades. A negative predictive value of > 90% has been reported for temporal artery biopsy; however, a negative result does not reliably indicate the absence of GCA because inflammation of the temporal artery is not always evident because of segmental involvement or other reasons. This is demonstrated by a case study of a patient hospitalized following acute vision loss to the right eye whose glucocorticoid treatment was suspended after temporal artery biopsy revealed no evidence of GCA. The patient subsequently lost sight in the left eye 6 weeks after stopping glucocorticoid therapy. The specificity of temporal artery biopsy for the diagnosis of GCA is variable and influenced by many factors, including length of biopsy specimens, vasculitis in vessels other than the temporal artery (ophthalmic, retinal and posterior ciliary vessels), unilateral versus bilateral biopsy, expertise of the surgeon, interpretation of histology, effects of treatment and confounding factors such as atherosclerosis or other non-GCA diseases that can affect the temporal artery. Considering the limitations of temporal artery biopsy, collaboration and education between the clinician, the pathologist and the patient, taking into account a thorough examination of patient history, recognizing signs and symptoms, and potentially involving newer imaging studies with trained technicians and physicians, are essential in confirming or eliminating diagnosis of GCA.
The first temporal artery biopsy was performed at the Mayo Clinic in 1932, >40 years after GCA was first described in the medical literature, indicating how slow progress has been in this disease. Temporal artery biopsy has become intrinsic to the diagnosis of GCA; however, although >85 years have passed since the first procedure was performed, there is much uncertainty regarding the performance, interpretation and test characteristics of temporal artery biopsy. How could a patient have GCA without documentable (and therefore diagnostic) inflammation of the temporal artery? After all, GCA is often referred to as temporal arteritis. Unfortunately, there are many reasons this might happen. Appropriate care of patients with GCA depends critically on gaining insight into these reasons.
The stakes are high in making a diagnosis of GCA; the patient's vision and life are at risk if a diagnosis is missed. Conversely, an incorrect diagnosis of GCA can lead to inappropriate glucocorticoid use and associated morbidity, as well as to undertreatment if the patient has another form of vasculitis (e.g. an ANCA-associated vasculitis). For these reasons, understanding the power and limitations of temporal artery biopsy is crucial to the diagnosis and treatment of patients with suspected GCA.
Experience and caution are paramount in the interpretation and reporting of temporal artery biopsy findings and there is great danger in attaching too much certainty to a negative temporal artery biopsy result. This is illustrated by the following case.
Rheumatology. 2018;57(2):ii3-ii10. © 2018 Oxford University Press