1561 Geijer, et al: CT and radiography in sacroiliitis Personal non-commercial use only. The Journal of Rheumatology Copyright © 2007. All rights reserved. The Clinical Utility of Computed Tomography Compared to Conventional Radiography in Diagnosing Sacroiliitis. A Retrospective Study on 910 Patients and Literature Review MATSGEIJER,GROGADEHOLTGÖTHLIN,andJANH.GÖTHLIN ABSTRACT. Objective. Ankylosing spondylitis (AS) is a progressive, debilitating disease with complex symptoms, unclearetiologyandpathogenesis,anddifficultdiagnosis.Currentimagingmethodsareusefulindiag- nosingASandotherspondyloarthropathies,andarefrequentlyusedininvestigationsofsacroiliitis.The radiographicdiagnosisofsacroiliitishaslargeinterobservervariations.Computedtomography(CT)has been used for evaluation of sacroiliitis since 1979, and has been evaluated in several studies, most of them with a limited number of patients. These studies have shown a large number of false-negative results from radiography. Methods. Inaretrospectivestudyofclinicaldata,weevaluated910patientswithASwhowereexam- ined by radiography and CT within a 2-year period. The reported outcomes from radiography and CT were compared. Results. TheagreementbetweenradiographyandCTdatawasonlyfair,withakappavalueof0.2418. There were 35.0% false-positive radiography reports, 22.5% false-negative radiography reports, and 86.0% false-equivocal radiography reports. In total, 41.3% of all radiological reports gave a false answer.Whilethenumberoffalsenegativeswassimilartothatpreviouslyreported,thenumberoffalse positives was much higher than previously reported, and is probably similar to everyday radiology reporting. Conclusion. Our results indicate that the clinical utility of radiography for evaluation of sacroiliitis is limited. The high rate of inaccurate results should motivate the use of sectional imaging for its superi- or performance. (First Release June 15 2007; J Rheumatol 2007;34:1561–5) Key Indexing Terms: SPONDYLOARTHROPATHIES DIAGNOSIS ANKYLOSING SPONDYLITIS DIAGNOSIS TOMOGRAPHY X-RAYCOMPUTED RADIOGRAPHY COMPARATIVESTUDIES From the Department of Radiology, Sahlgrenska University Hospital, Gothenburg, Sweden. M. Geijer, MD; G.G. Göthlin, MD, PhD; J.H. Göthlin, MD, PhD. Address reprint requests to Dr. M. Geijer, Department of Radiology, Lund University Hospital, S-221 85 Lund, Sweden. E-mail: mats@geijer.info Accepted for publication March 19, 2007. Ankylosingspondylitis(AS)isaprogressive,debilitatingdis- easewithcomplexsymptomsandunclearetiologyandpatho- genesis. Diagnosis is difficult, and delayed diagnosis as well as unsatisfactory management and treatment is not uncom- mon 1 . There is frequently a delay of several years from the start of symptoms until the radiographic diagnosis of sacroiliitis 2 . Diagnostic imaging methods assist in the diagnosis of AS and other spondyloarthropathies, and are used frequently in examination for suspected sacroiliitis. Conventional radio- graphic evaluation of sacroiliitis is an important part of diag- nosticcriteriasuchastheNewYorkcriteria 3,4 . Itiswellknownthattheradiographicdiagnosisofsacroili- itishaslargeinterobservervariations 5,6 .Thismayaccountfor at least some of the variation in the reported frequencies of false-positive and false-negative diagnoses. Computed tomography (CT) has been used for evaluation of sacroiliitis since 1979 7 . Several studies report a large number of false- negative radiography examinations, whereas CT has been reported to show higher accuracy 8-11 . MostreportscomparingtheoutcomeofradiographytoCT ormagneticresonanceimaging(MRI)arebasedonsmallpop- ulations and few controls 9-24 . These studies evaluated differ- entdiseasesofthesacroiliac(SI)joints.Onlyonestudyeval- uatedalargernumberofpatients 25 .Thesereportshaveshown that CT and MRI have higher sensitivity and specificity than radiographyforthediagnosisofsacroiliitis.Ithasbeenadvo- catedthatradiographyshouldbetheinitialradiologicalexam- ination and additional imaging should be done only when the radiographic results do not support the clinical diagnosis 26 . Wecarriedoutaretrospectivestudytoassesstheutilityof CTreportscomparedtoradiographyreportsineverydayclin- ical practice in a large number of patients with AS. The assumption was that CT is more accurate than radiography, thus improving decision-making and clinical outcome as well www.jrheum.org Downloaded on April 23, 2021 from