title: Percentage of patients with spondyloarthritis in patients referred because of chronic back pain and performance of classification criteria: experience from the Spondyloarthritis Caught Early (SPACE) cohort.
abstract: OBJECTIVE
  The objectives of the study are to describe the Spondyloarthritis Caught Early (SPACE) cohort, present the performance of various SpA classification criteria and compare patients fulfilling the imaging arm with patients fulfilling the clinical arm of the Assessment of Spondyloarthritis international Society (ASAS) axSpA criteria on demographics, presence of SpA features and level of disease activity.
  
  
  METHODS
  Patients with back pain (≥3 months but ≤2 years, onset <45 years) visiting the rheumatology outpatient clinic of the Leiden University Medical Center were included in the SPACE cohort. Patients were classified according to the modified New York (mNY), ESSG, Amor and ASAS axSpA criteria. The sensitivity and specificity of criteria were tested against a rheumatologist's diagnosis.
  
  
  RESULTS
  In total, 157 patients were included; 92 patients fulfilled any criteria, 11 fulfilled the mNY (sensitivity 16.9%, specificity 100%), 68 the ESSG (sensitivity 64.6%, specificity 71.7%), 48 the Amor (sensitivity 47.7%, specificity 81.5%) and 60 the ASAS axSpA criteria (sensitivity 84.6%, specificity 94.6%). Of those 60 patients, 30 fulfilled the imaging arm and 30 the clinical arm. Patients in the imaging arm are statistically significantly more often male, have a longer symptom duration and less often a positive family history for SpA than patients fulfilling the clinical arm. Patients in both arms are very similar regarding all other SpA features and level of disease activity.
  
  
  CONCLUSIONS
  The inclusion criteria of the SPACE cohort yield the same high numbers of SpA patients compared with referral strategies like inflammatory back pain, HLA-B27+ or sacroiliitis, yet are easier to apply. The ASAS axSpA criteria outperformed the other criteria; 38.2% fulfilled the ASAS axSpA criteria. Patients fulfilling the clinical arm of the ASAS axSpA reflect a group of patients similar to those fulfilling the imaging arm.
authors: Department of Rheumatology, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands.
authors: Rosaline
authors: R
authors: van den Berg
authors: Manouk
authors: M
authors: de Hooge
authors: Floris
authors: F
authors: van Gaalen
authors: Monique
authors: M
authors: Reijnierse
authors: Tom
authors: T
authors: Huizinga
authors: Désirée
authors: D
authors: van der Heijde
mesh_terms: D000328:Adult; D017677:Age Distribution; D000554:Ambulatory Care Facilities; D002908:Chronic Disease; D015331:Cohort Studies; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D017116:Low Back Pain / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D018579:Patient Selection; D011859:Radiography; D012017:Referral and Consultation / Q000145:classification* / Q000706:statistics & numerical data; D018570:Risk Assessment; D058566:Sacroiliitis / Q000145:classification / Q000000981:diagnostic imaging / Q000453:epidemiology; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017678:Sex Distribution; D012955:Societies, Medical; D025241:Spondylarthritis / Q000145:classification* / Q000000981:diagnostic imaging / Q000453:epidemiology*
keywords: classification criteria; diagnosis; referral; spondyloarthritis