title: How sensitive and specific are MRI features of sacroiliitis for diagnosis of spondyloarthritis in patients with inflammatory back pain?
abstract: OBJECTIVE
  To determine the sensitivity and specificity of MRI features of sacroiliitis in spondyloarthritis (SpA).
  
  
  METHODS
  A retrospective study reviewed MRI of the sacroiliac (SI) joints in 517 patients with inflammatory back pain. Sensitivity, specificity, positive and negative likelihood ratios of active and structural lesions of sacroiliitis with final clinical diagnosis as golden standard was calculated.
  
  
  RESULTS
  MRI showed active inflammation in 42% of patients (bone marrow oedema (BMO) (41.5%), capsulitis (3.3%), enthesitis (2.5%)) and structural changes in 48.8% of patients (erosion (25%), fat infiltration (31.6%), sclerosis (32%) and ankylosis (7.6%)). BMO was the MRI feature with the highest sensitivity (65.1%) for diagnosis of SpA. Capsulitis (99%), enthesitis (98.4%), ankylosis (97.4%) and erosion (94.8%) had a high specificity for diagnosis of SpA, whereas BMO (74.3%), sclerosis (75.8%) and fat infiltration (84.0%) were less specific. BMO concomitant with enthesitis, capsulitis or erosions increased the specificity. Concomitant presence of BMO and sclerosis or fat infiltration decreased the specificity.
  
  
  CONCLUSIONS
  BMO is moderately sensitive and specific for diagnosis of SpA in patients with inflammatory back pain. BMO concomitant with enthesitis, capsulitis, ankylosis or erosion increases the specificity. Concomitant fat infiltration or sclerosis decreases the specificity for diagnosis of SpA. Of all lesions, erosion had by far the highest positive likelihood ratio for diagnosis of SpA.
authors.affiliation: Department of  Radiology and Medical Imaging, Ghent University Hospital, Ghent, Belgium.  lennartjans@hotmail.com
authors.forename: L
authors.initials: L
authors.lastname: Jans
authors.forename: L
authors.initials: L
authors.lastname: Coeman
authors.forename: L
authors.initials: L
authors.lastname: Van Praet
authors.forename: P
authors.initials: P
authors.lastname: Carron
authors.forename: D
authors.initials: D
authors.lastname: Elewaut
authors.forename: F
authors.initials: F
authors.lastname: Van den Bosch
authors.forename: J L
authors.initials: JL
authors.lastname: Jaremko
authors.forename: W
authors.initials: W
authors.lastname: Huysse
authors.forename: K L
authors.initials: KL
authors.lastname: Verstraete
mesh_terms: D000293:Adolescent; D000328:Adult; D001416:Back Pain / Q000209:etiology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007249:Inflammation / Q000175:diagnosis / Q000209:etiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012189:Retrospective Studies; D012446:Sacroiliac Joint / Q000473:pathology*; D058566:Sacroiliitis / Q000150:complications* / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D025241:Spondylarthritis / Q000150:complications* / Q000175:diagnosis*; D055815:Young Adult