Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


The New ASAS Criteria for Axial SpA Does Not Predict the Development of mNYC AS at 8 Years in a Cohort of Very Early IBP Patients.

Aydin2,  Sibel Z., Bennett1,  Alex, Emery2,  Paul, McGonagle2,  Dennis, Marzo-Ortega2,  Helena

Defence Medical Rehabilitation Centre, Headley Court, Epsom, Surrey, United Kingdom
Section of Musculoskeletal Diseases, The Leeds Institute of Molecular Medicine. University of Leeds, Leeds, United Kingdom

Objective:

Axial SpA can be identified by using the new ASAS criteria. We aimed to test the predictive value of the imaging (MRI) and HLA-B27 arms of these criteria for the future development of Ankylosing Spondylitis (AS).

Method:

An inception cohort of 33 patients with early inflammatory back pain (IBP) (median symptom duration 24 weeks) were retrospectively evaluated against both arms (imaging and HLA-B27) of the criteria. Plain radiographs and MRIs of the SIJs at baseline and radiographs after a mean duration of 8-years were assessed. MRIs were scored according to the ASAS definition of a "positive MRI" and the predictive value of both arms was compared. Further scoring to identify patients with severe MRI sacroiliitis (grade 3 according to the Leeds MRI SIJ Scoring System) was also available.

Results:

All patients could be classified as axial SpA with more patients fulfilling the imaging (85%, n=28/33) than the clinical arm (58%, n=19/33) of the criteria. Eight patients with baseline evidence of radiographic sacroiliitis fulfilling the mNYC were excluded from the predictive analysis. Of the rest (25/33), n=4 patients developed AS at follow-up (all had a positive baseline MRI and 2 were HLA-B27+ve) and 11/33 had an increase in the radiographic sacroiliitis scores at 8 years. For prediction of new AS the MRI arm showed 100% sensitivity and 19% specificity whereas the HLA-B27 arm had 50% sensitivity and 43% specificity. No differences were seen between both arms for developing new AS or for progression of sacroiliitis when applying the ASAS definition of a positive MRI.

However an association was seen between development of AS (PPV 67%, NPV 91%, LR: 10) and progression of sacroiliitis (PPV 71%, NPV 76%, LR: 4.8) when using the Leeds definition of severe MRI sacroiliitis.

Conclusion:

Neither arm of the new ASAS classification criteria predicted the progression of radiographic sacroiliitis (including the development of mNYC AS) over an 8 year period in this cohort of very early IBP. This may be due to the inclusion of "mild" MRI sacroilitis in the ASAS definition of a "positive MRI" since severe MRI sacroiliitis was a better predictor.

Table 1. New AS or worsening of sacroiliitis by X-rays according to the MRI findings and HLA-B27 positivity

  Positive MRI (ASAS definition)Severe MRI (Leeds Scoring System)HLA-B27
  +-p+-p+-p
New AS (mNYC) n = 25+401220.057221
 -174 120 129 
Progression of sacroiliitis n = 33+1010.6560.03740.7
 -174 219 1110 

To cite this abstract, please use the following information:
Aydin, Sibel Z., Bennett, Alex, Emery, Paul, McGonagle, Dennis, Marzo-Ortega, Helena; The New ASAS Criteria for Axial SpA Does Not Predict the Development of mNYC AS at 8 Years in a Cohort of Very Early IBP Patients. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :553
DOI: 10.1002/art.28322

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