Computed Tomography Does Not Support Sacroiliitis as a Feature of Behçet Disease

To the Editor: Whether sacroiliitis is a feature of Behçet disease (BD) has been a subject of debate for many years. Some authors have found a high prevalence of sacroiliitis, whereas others have found no association at all. High observer variation in interpreting radiographs of sacroiliac joints (SI) has been suggested as the main cause of these differing results. Computed tomography (CT) is known as a more sensitive technique than plain radiographs in early detection and definition of SI changes, and has been recommended for more precise imaging in patients with equivocal sacroiliitis on plain films. Our aim was to study the SI changes seen on plain films of patients with BD by means of CT, along with 2 different control groups consisting of healthy subjects and patients with rheumatoid arthritis. Because widely differing prevalences of sacroiliitis have been found in different series of patients with BD, we also aimed to perform a metaanalysis of these results. Standard anteroposterior radiographs of the SI joints of 134 patients fulfilling International Study Group Criteria for BD were evaluated. One control group consisted of 14 ageand sexmatched healthy subjects. A second control group consisted of 15 ageand sex-matched patients with rheumatoid arthritis. Radiographs were mixed with those of the control patients and were read by a radiologist (IT) and a rheumatologist (NK) twice within 2 months. They were unaware of the diagnosis. Each SI was scored separately using the New York Criteria on a 0–4 scale (0 normal, 1 suspicious, 2 possible or minimal, 3 moderate changes, 4 ankylosis of the SI). In case of disagreement, radiographs were read again together and a reconciled grade was accepted. In a second step, each patient and control subject with a diagnosis of sacroiliitis on plain film had a sacroiliac CT scan. The CT scans were graded according to New York Criteria on the same scale by the same observers without any knowledge of the plain film findings. Metaanalysis was performed after the literature review for relevant papers. Ten articles related to the subject was found and reviewed. Five of them were found suitable for inclusion in the metaanalysis. They were dealing with the prevalence of sacroiliitis, so fixed-effects model (Peto) was used. Tests of heterogeneity of the effect size were conducted to determine whether one or more studies exerted an unusually large influence on the results or its effect size differed substantially from those of the other studies. Kappa values were calculated and chi-squared test was used. Thirty-one patients with BD (16 men and 15 women) had a mean age of 35.9 9.1 year (range, 16–60 years) with a mean disease duration of 7.1 5.8 years (range, 1–20 years). The healthy control group consisted of 7 men and 7 women with a mean age of 32.5 10.9 years (range, 18–52 years), In the group of patients with rheumatoid arthritis, 7 men and 8 women had a mean age of 37.5 10.0 years (range, 25–50 years). The groups were statistically similar (P 0.05). Of the 134 radiographs of patients with BD, 31 were evaluated as having sacroiliitis (23.1%). Two patients had bilateral grade 3 sacroiliitis, 1 patient unilateral grade 3, 2 patients had grade 2 on one side and grade 3 on the other side (Table 1). Two patients had unilateral grade 2 sacroiliitis. The rest of the 24 patients had equivocal findings: bilateral or unilateral grade 1 lesions. None of the patients had clinical evidence of sacroiliitis. Two patients (14.2%) in the healthy control group and 2 patients (13.3%) in the rheumatoid arthritis group had unilateral grade 2 sacroiliitis. CT confirmed sacroiliitis in 7 of 31 patients in the BD group (22.5%) and eliminated inflammatory sacroiliitis in the rest of the patients with equivocal sacroiliitis (Figs. 1 and 2). For plain films, the intraobserver variation (kappa value) for the first observer (IT) was 0.74; for the second observer (NK), it was 0.69. The interobserver variation was 0.78. For CT images, these values were 0.90, 0.80, and 0.78, respectively. When we performed metaanalysis with these 5 studies, we found the chisquared value for heterogeneity was 19.47 with an odds ratio of 2.27 (95% confidence interval [CI], 1.49–3.46) (P 0.001). When the metaanalysis was repeated without Dilsen’s study; the chisquared value for heterogeneity was calculated as 7.0872; the table value for the chi-squared test was 7.82 with an odds ratio of 0.78 (95% CI, 0.38–1.62). Although 7.09 7.82, we accepted this result as homogenous; also, it was quite significant (P 0.045). Examining the individual studies included in this metaanalysis, there are 2 studies that showed significantly higher prevalences of sacroiliitis over control groups. Yazıcı et al. found the prevalence of sacroiliitis as 35.1% in patients with BD versus 56.5% in the control group. Dilsen et al. stated this ratio as 36.8% and 5%, respectively. These studies reported the prevalence of sacroiliitis in diseased groups similarly, whereas the main conflict was in the control groups. Dilsen et al. found the sacroiliitis prevalence in the control group as 5%; but this ratio was 56.5% in the other study, debating against the idea of sacroiliitis being the feature of BD like other spondyloarthropathies. Some years later, Olivieri et al. conducted a similar study by CT scan and announced similar results as Dilsen’s study. The prevalence of sacroiliitis was 30% in the BD group versus 5% in the control group. Chamberlain et al. calcu-