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22-10-2018 | Giant cell arteritis | ACR/ARHP 2018 | News

Support for PET imaging in early giant cell arteritis diagnosis


medwireNews: Imaging with a combined positron emission tomography (PET) and computed tomography (CT) scanner shows good accuracy for diagnosing giant cell arteritis (GCA) versus the gold-standard temporal artery biopsy.

Advancements in PET scanning in the past 5 to 10 years now mean that imaging can be used to visualize the key vessels involved in GCA, namely the large arteries in the chest and the carotid arteries, study presenter Anthony Sammel, from Royal North Shore Hospital in Sydney, Australia, explained to the press at the 2018 ACR/ARHP Annual Meeting in Chicago, Illinois, USA.

The team used newer generation PET/CT time-of-flight scanners to scan 64 patients suspected of having GCA from the vertex to the diaphragm. Imaging was carried out within 72 hours of patients receiving corticosteroids and before they underwent temporal artery biopsy.

Of 58 who had a gold-standard biopsy, 12 (21%) patients tested positive for GCA and 11 of the 12 also tested positive on PET/CT scan, giving a sensitivity of 92%. The specificity was 85%, with 39 of the 46 patients testing negative on biopsy also showing a negative PET/CT scan result. The positive predictive value was 61% and the negative predictive value was 98%.

Sammel also noted that scanning revealed other useful information, which may not have been seen by ultrasound imaging, biopsy, or scalp magnetic resonance imaging.

“The first was that we managed to identify alternative diagnoses in one in five patients,” he said, explaining that the symptoms of GCA can often be mistaken for cancer or infection.

Indeed, Sammel reported that PET/CT scanning identified acute infection in seven patients and a serious neck infection mimicking GCA in one patient, who if treated with corticosteroids for 2 weeks while waiting on a biopsy could have come to serious harm. The team also identified five cancers and one case of thyroid disease.

Further to this, scanning identified five of the 12 patients testing positive for GCA as having inflammation of their aorta, a group of concern for rheumatologists due to the risk for aortic rupture.

Sammel concluded that “PET/CT scan when we include the arteries of the head, neck, and chest has very good diagnostic accuracy for giant cell arteritis.”

He continued: “We believe this study will support its use as a suitable first-line test for giant cell arteritis and for a significant number of patients it may mean that they don’t have to go on to perform a temporal artery biopsy.”

By Lucy Piper

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