Characteristics and axSpA classifications of the general VHA population and the chart review sample.
| Patients From General Population With ≥ 2 Encounters in VHA System, n = 79,826 | Chart Review Sample, axSpA-enriched Population, n = 300 | |||||||
|---|---|---|---|---|---|---|---|---|
| N or mean | SD or % | 95% CI | N or mean | SD or % | 95% CI | |||
| Age, yrs, at the cohort entry* | 58.1 | 17.8 | 58.0 | 58.2 | 54.7 | 17.7 | 52.7 | 56.7 |
| Sex, male | 74,359 | 93.2 | 93.0 | 93.3 | 277 | 92.3 | 88.8 | 94.8 |
| Race | ||||||||
| White | 55,830 | 69.9 | 69.6 | 70.3 | 212 | 70.7 | 65.3 | 75.5 |
| Black | 11,269 | 14.1 | 13.9 | 14.4 | 42 | 14.0 | 10.5 | 18.4 |
| Other | 4490 | 5.6 | 5.5 | 5.8 | 23 | 7.7 | 5.2 | 11.2 |
| Unknown | 8237 | 10.3 | 10.1 | 10.5 | 23 | 7.7 | 5.2 | 11.2 |
| Ethnicity | ||||||||
| Non-Hispanic | 67,589 | 84.7 | 84.4 | 84.9 | 262 | 87.3 | 83.1 | 90.6 |
| Hispanic | 4326 | 5.4 | 5.3 | 5.6 | 16 | 5.3 | 3.3 | 8.5 |
| Unknown | 7911 | 9.9 | 9.7 | 10.1 | 22 | 7.3 | 4.9 | 10.9 |
| Geographic region at cohort entry | ||||||||
| Continental | 13,151 | 16.5 | 16.2 | 16.7 | 49 | 16.3 | 12.6 | 20.9 |
| Midwest | 17,521 | 22.0 | 21.7 | 22.2 | 62 | 20.7 | 16.5 | 25.6 |
| North Atlantic | 19,137 | 24.0 | 23.7 | 24.3 | 82 | 27.3 | 22.6 | 32.6 |
| Pacific | 14,391 | 18.0 | 17.8 | 18.3 | 57 | 19.0 | 15.0 | 23.8 |
| Southeast | 15,626 | 19.6 | 19.3 | 19.9 | 50 | 16.7 | 12.9 | 21.3 |
| Health characteristics | ||||||||
| Charlson Comorbidity Index* | 2.1 | 2.8 | 2.1 | 2.2 | 2.6 | 2.9 | 2.3 | 2.9 |
| HLA-B27-positivea* | 74 | 0.09 | 0.07 | 0.12 | 24 | 8.0 | 5.4 | 11.6 |
| Low back painb* | 2.29 | 7.1 | 2.2 | 2.3 | 5.67 | 12.0 | 4.3 | 7.0 |
| Exposure to ≥ 1 nonbiologic DMARD* | 1292 | 1.6 | 1.5 | 1.7 | 64 | 21.3 | 17.1 | 26.3 |
| Exposure to ≥ 1 biologic DMARD* | 410 | 0.5 | 0.5 | 0.6 | 66 | 22.0 | 17.7 | 27.0 |
| VA system utilization | ||||||||
| Duration in the VA system* | 6.5 | 3.5 | 6.5 | 6.5 | 7.7 | 3.1 | 7.3 | 8.0 |
| No. encounters per year, meanc* | 26.9 | 44.9 | 26.6 | 27.2 | 37.9 | 38.4 | 33.6 | 42.3 |
| Classified as axSpA | ||||||||
| Chart review | NA | NA | NA | NA | 91 | 30.3 | 25.4 | 35.8 |
| Full algorithm* | 126 | 0.16 | 0.13 | 0.19 | 126 | 42.0 | 36.6 | 47.7 |
| High feasibility algorithm* | 140 | 0.18 | 0.15 | 0.21 | 122 | 40.7 | 35.3 | 46.3 |
| Early algorithm* | 409 | 0.51 | 0.47 | 0.56 | 158 | 52.7 | 47.0 | 58.3 |
| ≥ 2 AS codes, any specialty* | 105 | 0.13 | 0.11 | 0.16 | 105 | 35.0 | 29.8 | 40.6 |
| ≥ 2 AS codes, rheumatology* | 49 | 0.06 | 0.05 | 0.08 | 49 | 16.3 | 12.6 | 20.9 |
↵*P value < 0.05.
↵a Among veterans with clinically available HLA-B27 test results.
↵b Defined as > 1 low back pain ICD code (724.2x, M54.5x).
c Encounters included outpatient provider visits and ancillary services (pharmacy, laboratory, radiology, physical therapy, social work, nutrition, chiropractic services, etc.). AS: ankylosing spondylitis; axSpA: axial spondyloarthritis; DMARD: disease-modifying antirheumatic drug; ICD: International Classification of Diseases; NA: not applicable; VA: Veterans Affairs; VHA: Veterans Health Administration.