PET/CT compared with temporal artery biopsy for giant cell arteritis

Diagnosing giant cell arteritis (GCA) remains challenging due to the limitations of current diagnostic methods. Temporal artery biopsy (TAB) has long been considered the gold standard, but it is invasive and may miss active inflammation in non-biopsied segments. Non-invasive imaging techniques like PET/CT have gained attention for their potential to assess inflammation in a broader vascular context. However, the accuracy of PET/CT in comparison to TAB has not been fully established. Prior research has shown that TAB has limitations in sensitivity and may not capture the full extent of arterial involvement. This gap motivated a closer examination of how PET/CT performs relative to TAB in diagnosing GCA. Additionally, the influence of glucocorticoid treatment on diagnostic outcomes remains unclear. No prior work had resolved whether early glucocorticoid use affects the diagnostic accuracy of these tools. This uncertainty drove the need for a study that directly compares these diagnostic approaches in a real-world clinical setting.

The primary aim of this study was to evaluate the diagnostic performance of PET/CT in comparison to temporal artery biopsy for detecting GCA in patients suspected of the condition. The secondary objective was to assess how glucocorticoid treatment, administered before diagnostic testing, might influence the accuracy of each method. The researchers sought to determine whether PET/CT could serve as a reliable alternative or complement to TAB in GCA diagnosis. They also aimed to quantify the agreement between the two diagnostic methods and evaluate their sensitivity in relation to a clinical diagnosis confirmed after follow-up. The study was designed to address the limitations of TAB, such as its invasiveness and potential for sampling bias. By comparing PET/CT and TAB in a cohort of patients, the researchers hoped to provide evidence on the relative strengths and weaknesses of each diagnostic approach. This work could inform clinical decisions about diagnostic testing in patients with suspected GCA.

The researchers conducted a retrospective cohort study involving 157 patients suspected of GCA who underwent either temporal artery biopsy (TAB) or both TAB and PET/CT. The study population was divided into two groups: a TAB-only group and a PET/CT + TAB group. Clinical diagnosis of GCA was determined after a minimum six-month follow-up period. PET/CT scans were analyzed for signs of arterial inflammation, while TAB results were based on histopathological findings. The sensitivity of each diagnostic method was calculated in relation to the clinical diagnosis. The agreement between PET/CT and TAB was assessed using a negative agreement rate. The study also examined how the timing of glucocorticoid treatment affected diagnostic accuracy. Statistical analysis included confidence intervals and z-tests to compare sensitivities between methods. The study design allowed for a direct comparison of the two diagnostic tools in a real-world clinical setting.

The study found that the sensitivity of PET/CT was 76% (95% CI: 63-90%) compared to the clinical diagnosis of GCA. The sensitivity of TAB was 63% (95% CI: 48-78%), with no significant difference between the two methods (p = 0.2). In 15 cases, the results of PET/CT and TAB did not match, indicating variability in diagnostic outcomes. The negative agreement rate between PET/CT and TAB was 19% (95% CI: 11-29%), suggesting limited concordance between the two methods. When PET/CT and TAB were performed within three days of glucocorticoid therapy, their sensitivities increased to 85% (95% CI: 72-99%) and 74% (95% CI: 58-91%), respectively. This suggests that early glucocorticoid treatment may improve diagnostic accuracy. The study also found that PET/CT could detect inflammation in both cranial and extra-cranial arteries, which TAB cannot assess. These results support the potential utility of PET/CT in diagnosing GCA across a broader vascular spectrum.

The authors concluded that PET/CT is a useful imaging modality for diagnosing GCA, particularly in detecting inflammation in both cranial and extra-cranial arteries. The study supports the idea that PET/CT may offer advantages over TAB in terms of non-invasiveness and broader vascular assessment. However, the authors did not propose that PET/CT should replace TAB entirely, as both methods have comparable sensitivities. The findings suggest that early glucocorticoid treatment may enhance the diagnostic accuracy of both PET/CT and TAB. The researchers propose that PET/CT could be used in conjunction with TAB to improve diagnostic confidence in patients with suspected GCA. The study also highlights the importance of timing in diagnostic testing, as glucocorticoid therapy within three days may improve sensitivity. The authors did not suggest that PET/CT is superior to TAB in all cases, but they do propose it as a valuable tool in the diagnostic arsenal for GCA. These conclusions are based on the observed outcomes in the study cohort and the statistical comparisons made between the two diagnostic methods.