Dr Anthony Samuel

The 2017 Arthritis Australia and State/Territory Affiliate Translational Grant, kindly funded by Arthritis South Australia, allowed us to run a productive research program into giant cell arteritis (GCA). GCA is an inflammatory condition of blood vessels which can cause sudden onset blindness, joint stiffness, headache, fevers and jaw pain in older people. The current best test to make the diagnosis is a temporal artery biopsy. This involves surgery to remove a small piece of the artery on the side of the head. Our key objective was to test a new type of positron emission tomography (PET) scan in patients suspected of having this condition to see if it was better at diagnosing the condition than the biopsy. The new scanner allowed us to see active disease in arteries in regions of the head and neck that could not be seen on older PET scanners.

We enrolled a total of 64 patients in the study. All patients were initially suspected by their doctors as having GCA and had been treated for less than three days. This made them a perfect group to test the accuracy of the new scan. Patients undertook a survey, clinical examination, blood tests, PET scan and temporal artery biopsy. They were then followed up at three monthly intervals. Some patients had a second PET scan at 6 months.

We have published two articles in peer reviewed medical journals describing our findings and presented results at the Australian Rheumatology Association and American College of Rheumatology conferences in 2017. We are currently in the process of finalising the PET results for our full group of 64 patients. Once complete, we will know if the scan can be used to accurately diagnose GCA and whether it can predict how aggressively the disease will behave in the first two years.

The main question we sought to answer was whether our new PET scan technique was accurate in diagnosing GCA. A fast and accurate diagnosis is critical for this condition, as early treatment prevents both sudden onset vision loss and the characteristic debilitating symptoms of headache, joint stiffness and fevers. It also minimises the risk of treating the wrong condition in those who have a different illness. The current ‘best’ diagnostic test is a temporal artery biopsy which is problematic in that it is negative in a significant number of patients who have the disease. It also requires the patient to undergo surgery.

We also wanted to determine if the PET scan could help predict which patients would develop vision loss, widened arteries or flares of disease when treatment was reduced. This knowledge could help doctors tailor treatment plans to individual patients. We made significant research discoveries with the assistance of the grant. The first was to show that key arteries in the scalp and neck, namely the temporal, occipital and vertebral arteries, can reliably be visualised on our new PET scan and are often inflamed. These arteries are known to be involved in GCA but had been poorly seen on older scanners. Importantly, 6 of our first 41 patients had PET abnormalities limited to these three arteries. Their diagnosis may have been missed using older scanners.

The second discovery was to identify the location of the maxillary artery, an artery near the jaw that supplies the chewing muscles, on PET scan and show that it also has signs of inflammation in a proportion of patients with GCA. Active inflammation may be the cause of jaw pain in GCA patients because the chewing muscles are starved of blood.

We are currently analysing the scans, biopsy and six-month diagnoses of all 64 patients to determine the  if scans are reliably positive in the correct patients. In 2019 we will have long-term follow-up on all our patients to determine how well PET scans predict artery blockages, widening and disease flares.

We have disseminated our research findings through the publication of two peer reviewed journal articles and five conference presentations. Further publications are planned for the coming year.

Once results are finalised in late 2018, we will know if the new PET scan is accurate in diagnosing GCA. If it is shown to be accurate, future patients may be able to forgo a surgical procedure (temporal artery biopsy) and be at a reduced risk of blindness and symptoms of joint stiffness, headache and jaw pain because of delayed treatment.

The research program facilitated by this Arthritis Australia Grant will be continued into the foreseeable future. The grant has allowed us to establish a large group of suspected GCA patients who all have had PET scans, multiple clinical assessments and blood tests. Future work beyond that specified above includes:

– Assessing a range of new blood tests for GCA

– Fine-tuning PET scan settings and reporting techniques

– Assessing how well PET predicts long-term disease outcomes