Ultrasound, PET/CT or temporal artery biopsy for giant cell arteritis? A prospective diagnostic accuracy study (the
Michael S Hansen1,2, Lene Terslev2,3, Uffe M Døhn3
1Department of Ophthalmology, Rigshospitalet, Copenhagen, Denmark.
Purpose:
To investigate the diagnostic performance of ultrasound, 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography (2-[18F]FDG PET/CT) and temporal artery biopsy (TAB) in giant cell arteritis (GCA).
Methods:
This was a prospective single-centre diagnostic accuracy study (ClinicalTrials.gov NCT05248906). One hundred and ten patients suspected of GCA were considered, of which 103 were analysed, 100 had a final diagnosis and 58 had complete data for all modalities. Ultrasound, 2-[18F]FDG PET/CT and TAB were performed after clinical examination and blood sampling. The main outcome included diagnostic accuracy measures with final clinical expert diagnosis at 6-month follow-up as the comparator.
Results:
Sixty-one patients had GCA, 39 had non-GCA and 3 had inconclusive. The sensitivities were 82% (95% CI: 66%-92%), 74% (95% CI: 57%-87%) and 68% (95% CI: 51%-83%) for ultrasound, 2-[18F]FDG PET/CT and TAB, respectively. The corresponding specificities were 90% (95% CI: 68%-99%), 100% (95% CI: 83%-100%) and 100% (95% CI: 83%-100%), the positive predictive values 94% (95% CI: 81%-98%), 100% (95% CI: 88%-100%) and 100% (95% CI: 87%-100%), the negative predictive values 72% (95% CI: 57%-84%), 67% (95% CI: 54%-77%) and 63% (95% CI: 51%-73%) and accuracies 85% (95% CI: 73%-93%), 83% (95% CI: 71%-91%) and 79% (95% CI: 67%-89%). When ultrasound was inconclusive, 2-[18F]FDG PET/CT had a higher sensitivity of 75% (95% CI: 35%-97%) vs. 38% (95% CI: 9%-76%) for TAB, with equal specificity of 100% (both 95% CI: 69%-100%). Results were inconclusive in 22 of 99 ultrasounds, 3 of 102 2-[18F]FDG PET/CTs and 4 of 90 TABs.
Conclusion:
Ultrasound had high diagnostic accuracy for GCA, supporting this as the first imaging modality in suspected GCA. 2-[18F]FDG PET/CT combined a high diagnostic accuracy with fewer inconclusive results, suggesting it may be used for second-line testing when ultrasound is inconclusive, reserving TAB for third-line testing. A fast-track setup may facilitate efficient diagnostics.
