Diabetes screening necessary in patients with GCA and polymyalgia rheumatica

Irish Society for Rheumatology Spring Meeting, Virtual, 13 May 2021

Dr Sarah Mackie, Consultant Rheumatologist and Associate Professor at the University of Leeds, presented to delegates at the Irish Society for Rheumatology (ISR) Spring Meeting, which was held virtually on 13 May, on the subject of polymyalgia rheumatica and giant cell arteritis (GCA). Dr Mackie provided an overview of a systematic review and meta-analysis of 68 studies, including 14,037 patients who had suspected GCA. Findings of the meta-analysis revealed that where the likelihood ratio of a symptom was greater than one, it was likely that GCA was present, whereas when the likelihood ratio was less than one, it was unlikely that GCA was present.

While each of the four existing methods of assessing pre-test probability in GCA has its benefits and limitations, Dr Mackie highlighted the necessity of addressing diagnostic uncertainty while utilising and tweaking the chosen method to fit specific settings. Dr Mackie referenced the British Society of Rheumatology (BSR) guidelines on the diagnosis and treatment of GCA, which were published in January 2020 and accredited by the UK National Institute of Health and Care Execellence (NICE). BSR guidelines addressed the limitations of the assessment methods by recommending that each patient is referred to a specialist who has experience of diagnosing GCA (a rheumatologist), and an ultrasound, or biopsy, or both should be obtained.

Unlike GCA, before engagement with rheumatology, polymyalgia rheumatica is usually treated by GPs with steroids. While MRI, PET-CT and PET-MRI can help in diagnosis, practical limitations mean that not all patients in the community receive such screening. As such, approximately 3 per cent of polymyalgia rheumatica patients in the UK are treated with disease-modifying antirheumatic drugs (DMARDs) and the level of care is inconsistent. It is possible that some of these patients will go on to develop GCA.

To ascertain how many patients with GCA or polymyalgia rheumatica go on to develop diabetes, Dr Mackie carried out a meta-analysis of observational studies and trials. This meta-analysis involved 3,743 patients and revealed that 30 per cent of the GCA patients go on to develop diabetes, while 6 per cent of patients with polymyalgia rheumatica do likewise.

A further study of a dataset from the Clinical Practice Research Datalink involved a group of 100,722 patients without diabetes, 32 per cent of whom had either GCA or polymyalgia rheumatica. In the 10 years since diagnosis, 13.9 per cent of these patients had developed diabetes. Given that treatment of both conditions involves the use of high doses of steroids, which can cause multisystem toxicity, Dr Mackie stated that diabetes screening is needed in patients with GCA and polymyalgia rheumatica.