Poddubnyy Denis, Callhoff Johanna, Spiller Inge, Listing Joachim, Braun Juergen, Sieper Joachim, Rudwaleit Martin
Department of Gastroenterology, Infectious Diseases and Rheumatology, Campus Benjamin Franklin, Charité Universitätsmedizin Berlin, Berlin, Germany.
Epidemiology Unit, German Rheumatism Research Centre, Berlin, Germany.
RMD Open. 2018 Dec 5;4(2):e000825. doi: 10.1136/rmdopen-2018-000825. eCollection 2018.
Inflammatory back pain (IBP), the key symptom of axial spondyloarthritis (axSpA), including ankylosing spondylitis, has been proposed as a screening test for patients presenting with chronic back pain in primary care. The diagnostic accuracy of IBP in the rheumatology setting is unknown.
Six rheumatology centres, representing secondary and tertiary rheumatology care, included routinely referred patients with consecutive chronic back pain with suspicion of axSpA. IBP (diagnostic test) was assessed in each centre by an independent (blinded) rheumatologist; a second (unblinded) rheumatologist made the diagnosis (axSpA or no-axSpA), which served as reference standard.
Of 461 routinely referred patients, 403 received a final diagnosis. IBP was present in 67.3%, and 44.6% (180/403) were diagnosed as axSpA. The sensitivity of IBP according to various definitions (global judgement, Calin, Berlin, Assessment of SpondyloArthritis international Society criteria for IBP) was 74.4%-81.1 % and comparable to published figures, whereas the specificity was unexpectedly low (25.1%-43.9%). The resulting positive likelihood ratios (LR+) were 1.1-1.4 and without major differences between sets of IBP criteria. The presence of IBP according to various definitions increased the probability of axSpA by 2.5%-8.4% only (from 44.6% to 47.1%-53.0%).
The diagnostic utility of IBP in the rheumatology setting was smaller than expected. However, this was counterbalanced by a high prevalence of IBP among referred patients, demonstrating the effective usage of IBP in primary care as selection parameter for referral to rheumatology. Notably, this study illustrates potential shifts in specificity and LR+ of diagnostic tests if these tests are used to select patients for referral.
炎性背痛（IBP）是包括强直性脊柱炎在内的轴性脊柱关节炎（axSpA）的关键症状，已被提议作为基层医疗中慢性背痛患者的筛查试验。IBP在风湿病环境中的诊断准确性尚不清楚。
六个代表二级和三级风湿病护理的风湿病中心纳入了常规转诊的、连续出现慢性背痛且怀疑患有axSpA的患者。每个中心由一名独立（盲法）风湿病学家评估IBP（诊断试验）；另一名（非盲法）风湿病学家做出诊断（axSpA或非axSpA），该诊断作为参考标准。
在461例常规转诊患者中，403例获得了最终诊断。67.3%的患者存在IBP，44.6%（180/403）被诊断为axSpA。根据各种定义（整体判断、卡林、柏林、国际脊柱关节炎评估协会IBP标准），IBP的敏感性为74.4%-81.1%，与已发表的数据相当，而特异性出乎意料地低（25.1%-43.9%）。由此得出的阳性似然比（LR+）为1.1-1.4，不同组的IBP标准之间没有重大差异。根据各种定义存在IBP仅使axSpA的概率增加了2.5%-8.4%（从44.6%增至47.1%-53.0%）。
IBP在风湿病环境中的诊断效用低于预期。然而，转诊患者中IBP的高患病率对此起到了平衡作用，表明IBP在基层医疗中作为转诊至风湿病科的选择参数有效。值得注意的是，本研究说明了如果将这些诊断试验用于选择转诊患者，其特异性和LR+可能会发生潜在变化。
