What is Giant Cell Arteritis?
Giant cell arteritis (GCA) is a serious form of vasculitis (inflammation of the blood vessels) which can result in irreversible ischaemic complications, including stroke and blindness.
GCA typically affects the temporal arteries, hence the alternative name of “temporal arteritis”.
GCA most commonly affects older individuals.
What are the signs and symptoms?
Patients can (but not always) present with headache, jaw claudication, temporal artery tenderness or fever. However, definitive diagnosis is challenging due to the non-specific and varied clinical presentation and the lack of a robust diagnostic biomarker. The temporal artery biopsy therefore remains the gold standard test in GCA diagnosis.
Patients with suspected GCA are immediately started on high-dose glucocorticoid therapy to prevent ischaemic complications.
What is the role of the temporal artery biopsy?
There is, unfortunately, no single quick blood test which can diagnose GCA.
The temporal artery biopsy is regarded as the gold standard test in GCA diagnosis and forms part of the core diagnostic criteria in all UK, European and American classification guidelines. Under current National Health Service (NHS) England prescribing guidance a TAB result is a component of the eligibility criteria for the biologic therapy tocilizumab.
What are the best practice guidelines for handling TABs?
The Royal College of Pathologists (RCPath) tissue pathways for cardiovascular pathology (2018) document outlines the best practice guidelines for the handling of temporal artery biopsies. These can be summarised as follows:
- It is recommended that the minimum length of TAB, post formaldehyde fixation, should be 5-10mm
- The length and diameter of the TAB should be measured
- The TAB should be sectioned transversely into segments 3-5mm in length
- The segments should be embedded on end
- All of the TAB should be submitted for histology as arteritis may be focal
Further information on TAB specimen submission, sectioning and staining and further investigations can be found in the RCPath tissue pathway for cardiovascular pathology document. The link to this document can be found in the “useful resources” section.
What are the issues with the reporting of TABs for the diagnosis of GCA?
Recent research has shown that there is disconcordance between histopathologists in the assessment and reporting of TABs for the diagnosis of GCA. An online survey of all consultant members of the RCPath conducted by our research team, AHEADgca, found the following:
- Most respondents expressed that there are no reporting guidelines or agreed reporting categories
- Multiple respondents commented that the criteria for what constitutes ‘positive for’ or ‘consistent with’ GCA is not clear, and that there is variation in the interpretation of certain microscopic appearances
- Timed change in histopathology due to steroid treatment are undefined
Giant cell arteritis can be challenging to diagnose on TAB for a number of reasons. These include, but are not limited to the following:
- Suboptimal sampling and subsequent handling of the temporal artery biopsy
- Biopsies may exhibit a variable extent of inflammatory involvement with segments showing no inflammation. This is often referred to as ‘skip lesions.’
- Making a definitive diagnosis of GCA can be difficult in TABs which also show features of age related changes or atherosclerosis.
Full list of the literature relevant to this section can be found in the “useful resources” section.
Links to useful resources regarding GCA:
https://patient.info/doctor/giant-cell-arteritis-pro
https://cks.nice.org.uk/topics/giant-cell-arteritis/
Organisations offering help and support for patients living with GCA
Vasculitis UK: https://www.vasculitis.org.uk/about-vasculitis/giant-cell-arteritis-temporal-arteritis
HealthUnlocked forum: https://healthunlocked.com/
PMRGCAuk: https://pmrgca.org.uk/
