Table 1 Selection of patients sampled for the chart review population
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 | ||