Prevalence Of Axial Spondyloarthritis In Beijing Shougang Company

OBJECTIVES:This study conducted a questionnaire in Beijing Shougang Company, to determine prevalence of inflammatory back pain and axial Spondyloarthritis in Beijing Shougang Company and estimate prevalence of axial Spondyloarthritis in Beijing and adjacent district, and to validate the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial Spondyloarthritis in China.MEHTODS:A survey was conducted of 15357 subjects aged 17 years or over in 34 departments out of 50 departments of Beijing Shougang Company, selected by cluster sampling. Those who responded positively to the screening questions were contacted by 3 rheumatologists, suspected subjects were then screened with sacroiliac joints X ray and HLA-B27 typing by PCR. In the end,6 rheumatism specialists evaluated in detail to establish presence of axial SpA (The ASAS Classification Criteria for Axial SpA) and other subtypes, data obtained from the Chinese national census in the year 2005 were used as the reference population for standardization.RESULTS:(1) A total of 15357 subjects partiaipated in the study,12124 replied,731 patients with suspected inflammatory back pain were invited to hospital and took rart in the face-to-face survey and Physical examination.138 patients with suspected axial SpA were carried out pelvic X-ray dxamination and HLA-B27 test. Finally 68 cases of axial SpA were confirmed in 46 men and 22 women, AS was the most common subtype (38 cases), followed by uSpA (21 cases), PsA (6 cases),IBDA (2 cases) and ReA (only 1 case).(2) Among 138 patients with suspected axial SpA,65 cases had sacroiliitis, the patients with bilateral grade 2, grade 3, grade 4 and over grade 3 unilateral radiographic sacroiliitis were 27,18,9,7,4 respectively. Among 68 axial SpAs, HLA-B27 were positive in 64 patients, the prevalence of HLA-B27 was 94.1%. Other 70 patients, HLA-B27 were positive in 8 patients, the prevalence of HLA-B27 was 10.8%, it was lower than that in axial SpA (P<0.01).(3) The overall prevalence of axial SpA standardized for age and sex was 0.577% (95% CI 0.442 to 0.712), the prevalence of AS was 0.361% (95% CI 0.254 to 0.468). The prevalence of axial SpA was higher in women (male to female: 0.511% VS 0.851%) and the prevalence of AS among men was obviously higher than that in women (male to female:0.385% VS 0.283%).(4) The prevalence varied in different age groups, the highest prevalence was in the age from 17 to 29 years and decreased suddenly after the age of 40 years. The average age at onset and positive rate of HLA-B27 in men were similar to that in women (P>0.05). Inflammation of sacroiliac joints in men was remarkably higher than that in women (P<0.01).(5) Amor and ESSG criteria were examined in all 138 cases, the sensitivity and specificity of Amor criteria were 82.3% and 80.0%, which of ESSG criteria were 77.9% and 84.3%.CONCLUSIONs:(1) The new survey questionnaire for SpA in this study is useful for axial SpA screening in China. The prevalence of axial SpA standardized for age and sex in Shougang company was 0.577%, it was lower than other several researchs in our country. AS was the most common SpA subtype, followed by uSpA, PsA,IBDA and ReA.(2) The older studies have documented a clear male predominance in axial SpA and AS. A striking finding in our study that the prevalence of AS among men was obviously higher than that in women, but the overall prevalence of axial SpA was obviously higher in women. The prevalence varied in different age groups, the highest prevalence was in the age from 20 to 30 years.(3)Although IBP is the usual presenting symptom and one of the most important clinical features of axial SpA, it's insufficient for diagnosis of axial SpA. In our study, only 56.9% cases with IBP were confirmed axial SpA, it indicats that other assistant examinations were performed in establishing the diagnosis of axial SpA.(4)The sensitivities that the two sets of criteria showed for Chinese population in our study were 82.3% for Amor and 77.9 for ESSG, the specificities were 80.0% and 84.3%, respectively. It indicates that the adaptability of the 3 sets criteria to Chinese population was validated.