CT Scan Beats Radiograph for Diagnosing Sacroiliitis

Excellent inter-reader reliability of staging and ascertaining sacroliitis with CT scans

FRIDAY, Nov. 18 (HealthDay News) -- For patients with suspected spondyloarthritis (SpA), sacroiliitis is underestimated by radiography compared with computerized tomography (CT) scans, according to a study published online Nov. 11 in Arthritis & Rheumatism.

Valérie Devauchelle-Pensec, M.D., Ph.D., from the Université Européenne de Bretagne in Universit de Brest, France, and colleagues assessed the performance of CT scan for ascertaining sacroiliitis in 489 patients with suspected SpA. All participants underwent clinical examination, human leukocyte antigen-B typing, and pelvic radiography at baseline. The patients underwent a pelvic CT scan if sacroiliitis on the radiograph was considered uncertain or if they presented with buttock pain duration of more than six months. Two radiologists blindly read a set of 100 paired radiographs/CT scans, and their reliability was assessed using kappa coefficient.

The investigators found that inter-reader reliability for sacroiliitis staging was moderate on radiograph and excellent on CT scan. The inter-reader reliability for ascertaining sacroiliitis on both radiograph and CT scan was excellent. The two radiologists identified the quality of imaging as good in 66 and 67 percent of the radiographs, and 93 and 92 percent of the CT scans, respectively. Sacroiliitis staging or ascertainment by radiograph had low concordance with that done by CT scan. Definite sacroiliitis was ascertained in 3.5 and 18.5 percent of patients based on radiographs and CT scans, respectively. A significant association was seen between the history of uveitis and definite sacroiliitis on radiograph and CT scan.

"Definite sacroiliitis was underestimated by radiograph, as compared to CT scan. CT scan should facilitate the diagnosis of ankylosing spondylitis in patients with suspected SpA," the authors write.

The study was funded by Pfizer and Schering-Plough.

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