title: Application of the 2012 Systemic Lupus International Collaborating Clinics classification criteria to patients in a regional Swedish systemic lupus erythematosus register.
abstract: BACKGROUND
  In 2012, the Systemic Lupus International Collaborating Clinics (SLICC) network presented a new set of criteria (SLICC-12) to classify systemic lupus erythematosus (SLE). The present study is the first to evaluate the performance of SLICC-12 in an adult European study population. Thus, SLICC-12 criteria were applied to confirmed SLE cases in our regional SLE register as well as to individuals with a fair suspicion of systemic autoimmune disease who were referred to rheumatology specialists at our unit.
  
  
  METHODS
  We included 243 confirmed SLE patients who met the 1982 American College of Rheumatology (ACR-82) classification criteria and/or the Fries 'diagnostic principle' (presence of antinuclear antibodies on at least one occasion plus involvement of at least two defined organ systems) and 55 controls with possible systemic autoimmune disease, including the presence of any SLE-related autoantibody.
  
  
  RESULTS
  SLICC-12 showed a diagnostic sensitivity of 94% (95% confidence interval (CI), 0.90 to 0.96) compared with 90% (95% CI, 0.85 to 0.93) for the updated set of ACR criteria from 1997 (ACR-97), whereas ACR-82 failed to identify every fifth true SLE case. However, the disease specificity of SLICC-12 reached only 74% (95% CI, 0.60 to 0.84) and did not change much when involvement of at least two different organs was required as an indicator of systemic disease. In addition, SLICC-12 misclassified more of the controls compared to ACR-82, ACR-97 and Fries.
  
  
  CONCLUSIONS
  Establishing a standard definition of SLE continues to challenge lupus researchers and clinicians. We confirm that SLICC-12 has advantages with regard to diagnostic sensitivity, whereas we found the diagnostic specificity to be surprisingly low. To accomplish increased sensitivity and specificity figures, a combination of criteria sets for clinical SLE studies should be considered.
authors.affiliation: Rheumatology/AIR, Department of Clinical and Experimental Medicine, Linköping University, University Hospital, SE-581 85, Linköping, Sweden. anna.ighe@gmail.com.
authors.forename: Anna
authors.initials: A
authors.lastname: Ighe
authors.affiliation: Swedish Institute for Disability Research, Department of Behavioural Sciences and Learning, Linköping University, SE-581 83, Linköping, Sweden. orjan.dahlstrom@liu.se.
authors.forename: Örjan
authors.initials: Ö
authors.lastname: Dahlström
authors.affiliation: Rheumatology/AIR, Department of Clinical and Experimental Medicine, Linköping University, University Hospital, SE-581 85, Linköping, Sweden. thomas.skogh@lio.se.
authors.forename: Thomas
authors.initials: T
authors.lastname: Skogh
authors.affiliation: Rheumatology/AIR, Department of Clinical and Experimental Medicine, Linköping University, University Hospital, SE-581 85, Linköping, Sweden. christopher.sjowall@liu.se.
authors.forename: Christopher
authors.initials: C
authors.lastname: Sjöwall
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D038622:Internationality; D008180:Lupus Erythematosus, Systemic / Q000145:classification* / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012042:Registries; D012720:Severity of Illness Index; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult