Pairing PET with CT achieved better diagnostic accuracy than temporal artery biopsy (TAB) in patients with newly suspected giant cell arteritis (GCA), according to research presented at the 2018 American College of Rheumatology (ACR)/ Association of Reproductive Health Professional (AHRP) meeting in Chicago.
“Patients and their doctors increasingly seek non-invasive, timely, accurate and low-risk diagnostic tests,” said lead author Anthony M. Sammel, MD with Royal North Shore Hospital in Sydney, in a statement. “This is especially important for GCA, where symptoms are often non-specific, and a delay in diagnosis can lead to permanent vision loss.”
The Australian researchers enrolled 64 patients with newly suspected GCA over 20 months. All participants received PET/CT from the vertex to diaphragm within 72 hours of starting corticosteroid therapy prior to TAB. Two experienced nuclear medicine physicians analyzed the scans for GCA and graded the FDG tracer uptake in 18 artery segments.
Overall, PET/CT had a sensitivity of 92 percent, specificity of 85 percent, positive predictive value of 61 percent and negative predictive value of 98 percent. Of the 58 patients who underwent TAB, 21 percent had biopsies that were GCA-positive.
Sammel and colleagues noted that defining the uptake grade cut-off at 1-plus in any vessel as a positive scan resulted in PET/CT sensitivity of 100 percent and a specificity of 46 percent. A cut-off of two-plus achieved 83 percent sensitivity and specificity.
Although TBA is commonly used for GCA, the authors argued their PET/CT method could be used a first-line defense to rule out the disease.
“Rheumatologists could consider using this PET/CT scan protocol to help confirm or refute the diagnosis of acute GCA,” said Sammel in the same statement. “The study indicates that a negative scan may be particularly useful in ruling out the disease in patients who have a low pre-test probability of GCA.”