LAUSR

We welcome Dr Ing’s critique [1] of our review paper [2], which articulated the advances in Giant Cell Arteritis (GCA). His letter highlights the importance of reviews in a disease area where high-quality evidence is challenging as well as changing historical practice. We unequivocally support the need for a confirmatory test for GCA, given the seriousness of the disease and the significant adverse events from the cumulative glucocorticoid burden as recommended by evidence [3, 4] and through rigorous systematic literature review by guideline groups [5]. Ultrasound has many clear advantages over temporal artery biopsy (TAB). It is more sensitive than TAB in most studies, safe, non-invasive, repeatable, and allows many different arterial territories to be examined at one time [3, 4]. A recent meta-analysis of ultrasound use in GCA found a pooled sensitivity of 77% and specificity of 96% [4, 5]. Fast track pathways that utilise ultrasound have shown reduced rates of visual loss compared with their previous TAB-driven pathways [4]. However, we strongly agree that TAB still has a place where ultrasound does not rule in or rule out GCA, or is unavailable. There are many mimics of GCA, as detailed by Dr Ing [1]. However, in our collective experience, the diagnosis would not rest solely on the histopathology in isolation, without due consideration of a thorough history and examination. What constitutes a positive TAB is not black and white, for example atherosclerotic changes can be misinterpreted as healing GCA. A key point from TABUL was the inter-observer agreement for evaluation of biopsy vs ultrasound. Both tests provided only moderate levels of agreement when 12 sonographers (kappa 0.61) assessed 30 ultrasound videos and 14 pathologists (kappa 0.62) assessed 30 high-quality biopsy images [3]. It can be easy to be critical of study results, and indeed in TABUL when 381 biopsies were performed 28 (7.3%) did not return arterial tissue. Sadly, this reflects routine care within normal NHS practice. It is equally important to recognise the potential bias deriving from idealised practice within a single individual centre, with a dedicated surgeon obtaining TAB effectively, thereby considerably improving the sensitivity of the test. Whilst not wishing to undermine such practice, we should avoid using such audit data to popularise the incorrect assumption that such practice can be replicated readily, without a large change in how the service is provided. As to the controversy of a ‘gold standard’ for diagnosis in GCA, the use of this term originated from the widespread acceptance of gold as currency. Over time, various commodities have been used as money but typically, the ones that lose the least value over time have become the accepted form. TAB used to be the only confirmatory test available. Many clinicians in the United Kingdom now find it hard to access this ‘commodity’. By contrast, ultrasound, combined with careful physician judgement, has been proven to be superior to TAB both in diagnosis and in terms of cost effectiveness (ultrasound is almost ten times less expensive than TAB) [3]. Despite the fact that (TAB) gold is now a rare currency, it remains accessible when the (clinician) need requires it.