Severity of baseline magnetic resonance imaging–evident sacroiliitis and HLA–B27 status in early inflammatory back pain predict radiographically evident ankylosing spondylitis at eight years

Abstract

Objective. Magnetic resonance imaging (MRI) is increasingly used to detect sacroiliitis earlier. This study was undertaken to investigate what proportion of patients with MRI-evident sacroiliitis develop ankylosing spondylitis (AS) in the long term and whether there are predictors of outcome.Methods. Consecutive undiagnosed patients with early inflammatory back pain (IBP) (of <2 years' duration) were assessed clinically and radiologically. Baseline imaging assessments included fat-suppressed MRI sequences of the sacroiliac joints and lumbar spine that were scored for active bone marrow edema representative of acute inflammation, and anteroposterior radiographs of the pelvis and lateral radiographs of the lumbar spine, which were scored using the Stoke Ankylosing Spondylitis Spine Score. Patients were reassessed clinically and radiographically after 8 years. The primary outcome was the modified New York criteria for AS at followup.Results. Fifty patients were assessed at the beginning of the study, and 40 patients were followed up after a mean of 7.7 years. Of these 40 patients, 58% were HLA-B27 positive, and 98% met the European Spondylarthropathy Study Group criteria. The current diagnostic criteria for ankylosing spondylitis (AS), the modified New York criteria (1), rely on the presence of radiographically evident sacroiliitis, which may only appear after years of inflammatory back pain (IBP) (2). However, it is known that much of the pathologic condition in axial spondylarthritis (SpA) is related to perifibrocartilage osteitis, and magnetic resonance imaging (MRI) has been proven to be supe-1 A.

Development and Validation of a Magnetic Resonance Imaging Reference Criterion for Defining a Positive Sacroiliac Joint Magnetic Resonance Imaging Finding in Spondyloarthritis

“…This requirement is challenging in the early stages of the disease because structural changes on pelvic radiographs, which constitute the basis of the modified New York criteria for classifying SpA, may take Ͼ10 years to become apparent (6,7). Consequently, the expert opinion of clinicians has been used as a gold standard, which has obvious limitations associated with false-positive or false-negative assignments and ultimately still requires a lengthy followup period to ascertain the development of radiographic sacroiliitis.…”

“…Two interventional trials of nr-axSpA reported a symptom duration of 7-8 years and 10.1 years with HLA-B27 frequencies of 59 -75% and 70 -75%, respectively (22,23). In 2 prospective studies of SpA inception cohorts with 7.7 and 10 years of followup, only 33.3% and 24.3% of nr-axSpA patients, respectively, progressed to radiographic sacroiliitis, meeting the modified New York criteria (7,24). …”

Evaluation of the diagnostic utility of spinal magnetic resonance imaging in axial spondylarthritis

“…This is principally because the diagnostic radiographic changes in the SI joints and spine usually develop slowly (1). Fat-suppressed MRI enables identification of osteitis at disease presentation and has the potential to transform the diagnosis of axial SpA, since much of the axial pathology is related to a diffuse perifibrocartilage osteitis, either in the SI joints or at the entheses in the spine (2)(3)(4).…”

“…It is generally assumed that these MRI patterns of disease can be used to distinguish SpA from other diseases. Indeed, these lesions are being used to diagnose axial SpA early in its onset (3,8) and might influence early initiation of biologic therapy; for this purpose, several systems of scoring spinal BME lesions have been established (6,(9)(10)(11)(12). However, the specificity of these spinal BME lesions for SpA and their diagnostic utility for SpA have not been confirmed.…”

Ankylosing Spondylitis – the changing role of imaging

“…Furthermore, recent work has confirmed the predictive value of an abnormal MRI in a group of patients with early inflammatory back pain. The combination of severe BMO lesions (according to the Leeds MRI Scoring System) and a positive HLA B27 each gave a sensitivity and specificity of 77 % for the subsequent development of radiographic sacroiliitis [3]. These findings were confirmed in a separate prospective study.…”