Objectives
To investigate the performance of cranial PET/CT for the diagnosis of giant cell arteritis (GCA).
Methods
All patients with a suspected diagnosis of GCA were prospectively enrolled in this study and had a digital PET/CT with evaluation of cranial arteries if they had not started glucocorticoids more than 72 hours previously. The diagnosis of GCA was retained after at least 6 months of follow-up if no other diagnosis was considered by the clinician and the patient went into remission after at least 6 consecutive months of treatment. Cranial PET/CT was considered positive if at least one arterial segment showed hypermetabolism similar to or greater than liver uptake.
Results
For cranial PET/CT, sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) were 73.3%, 97.2%, 91.7% and 89.7%, respectively. For extracranial PET/CT, diagnostic performance was lower (Se = 66.7%, Sp = 80.6%, PPV = 58.8%, NPV = 85.3%). The combination of cranial and extracranial PET/CT improved overall sensitivity (Se = 80%) and NPV (NPV = 90.3%) while decreasing overall specificity (Sp = 77.8%) and PPV (PPV = 60%).
Conclusion
Cranial PET/CT can be easily combined with extracranial PET/CT with a limited increase in examination time. Combined cranial and extracranial PET/CT showed very high diagnostic accuracy for the diagnosis of GCA.
Trial registration
ClinicalTrials.gov, https://clinicaltrials.gov, NCT05246540.
Introduction
Giant cell arteritis (GCA) is a frequent granulomatous vasculitis. In the diagnosis of large vessel GCA, FDG-PET/CT imaging has been recommended and its use has steadily increased. The objective of this prospective study was to evaluate the diagnostic performance of digital FDG-PET imaging with a head and neck dedicated protocol, especially to detect cranial arteries involvement, using different visual grading scores, and to assess the inter-reader agreement.
Material and Methods
FDG-PET/CT scans with a 10-min acquisition time on the head and neck were performed in patients suspected of having recent GCA. A score including 20 segments due to the inclusion of cranial segments and a score established only for the cranial segments were compared to the Total Vascular Score (TVS) established on 7 arterial segments. These scores were assessed by two nuclear medicine physicians on a blinded manner and, in case of disagreement, a consensus was established with a third nuclear medicine physician.
Results
GCA diagnosis was retained for 15 of the 52 patients included. Sensitivity and specificity of the 20-segment or the cranial scores were higher than those of TVS (sensitivity and specificity of 80% of 97% for both scores vs 73% and 89% for TVS, respectively). The inter-reader agreement was substantial in the 20-segment score (weighted kappa = 0.68) but better in the cranial segments than other segments.
Conclusion
This study shows the usefulness of grading scores able to highlight involvement of cranial arteries in GCA with a better inter-reader agreement in cranial segments than other segments.
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