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Table 1 Selection of patients sampled for the chart review population

From: Cohort identification of axial spondyloarthritis in a large healthcare dataset: current and future methods

Subgroups Subgroup Criteria (ICD-9 or laboratory data) No. of Veterans No. of Veterans selected to chart review population % from each risk stratum selected to the chart review population (95% CI)
High risk for axSpA
 Ankylosing spondylitis 720.0 15,862 100 0.83 (0.72–0.96)
 HLA-B27 positivity positive B27 test result 8168 100
Moderate risk for axSpA
 Sacroiliitis 720.2 50,603 100 0.25 (0.21–0.28)
 SpA subtype other than AS    100a
  Spondyloarthritis NOS 720.8× and/or 720.9× 6319
  Reactive arthritis 711.x and/or 99.3 1072
  Psoriatic arthritis 696.0 22,625
  Enteropathic arthritis 713.1 AND either 555.x OR 556.x 521
Low risk of axSpA
 Chronic back pain (≥2 ICD-9 codes for back pain ≥3 months apart [724.1, 724.2, 724.5]) 2,069,644 100 0.01 (0.01–0.01)
 Non-SpA rheumatologic disease    100a
 DISH 721.6 2963
 Crystal arthritis 274.x and/or 712.x 675,799
 Rheumatoid arthritis 714.x 143,620
 Other inflammatory arthritis CTD (710.x), vasculitis (273.2, 446.0, 446.4, 446.5, 446.7), PMR (725), Paget’s (731.0), sarcoidosis (135) 135,608
  1. a25 patients from each subcategory of spondyloarthritis NOS, reactive arthritis, psoriatic arthritis, enteropathic arthritis, DISH, crystal arthritis, rheumatoid arthritis, and other inflammatory arthritis