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Table 2 Demographic characteristics of nonradiographic axial spondyloarthritis, ankylosing spondylitis, and other inflammatory back pain patients

From: The prevalence and clinical characteristics of nonradiographic axial spondyloarthritis among patients with inflammatory back pain in rheumatology practices: a multinational, multicenter study

  Total (N = 914) nr-axSpA (n = 266) AS (n = 491) Other IBP (n = 157) p Value
Sex      <0.001
 Male, n (%) 588 (64.33 %) 169 (63.53 %) 350 (71.28 %) 69 (43.95 %)  
  95 % CI (61.22–67.44) (57.74–69.33) (67.27–75.29) (36.17–51.73)  
 Female, n (%) 326 (35.67 %) 97 (36.47 %) 141 (28.72 %) 88 (56.05 %)  
  95 % CI (32.56–38.78) (30.67–42.26) (24.71–32.73) (48.27–63.83)  
Sex      <0.001
 Male, n (row %) 588 (100.00 %) 169 (28.75 %) 350 (59.52 %) 69 (11.73 %)  
  95 % CI   (25.08–32.41) (55.54–63.50) (9.13–14.34)  
 Female, n (row %) 326 (100.00 %) 97 (29.75 %) 141 (43.25 %) 88 (26.99 %)  
  95 % CI   (24.78–34.73) (37.86–48.64) (22.17–31.82)  
Age, years, mean ± SD 38.68 ± 12.02 34.75 ± 10.03 39.03 ± 11.38 44.26 ± 14.48 <0.001
Race/ethnicity      <0.001
 White, n (%) 596 (65.21 %) 148 (55.64 %) 335 (68.23 %) 113 (71.97 %)  
  95 % CI (62.11–68.30) (49.66–61.62) (64.10–72.35) (64.94–79.01)  
 Asian, n (%) 116 (12.69 %) 55 (20.68 %) 55 (11.20 %) 6 (3.82 %)  
  95 % CI (10.53–14.85) (15.80–25.55) (8.41–14.00) (0.82–6.83)  
 Black, n (%) 12 (1.31 %) 2 (0.75 %) 2 (0.41 %) 8 (5.10 %)  
  95 % CI (0.57–2.05) (0.00–1.79) (0.00–0.97) (1.65–8.54)  
 Unknown, n (%) 190 (20.79 %) 61 (22.93 %) 99 (20.16 %) 30 (19.11 %)  
  95 % CI (18.15–23.42) (17.87–27.99) (16.61–23.72) (12.95–25.27)  
BMI category      0.024
 Underweight, n (%) 55 (6.02 %) 12 (4.51 %) 38 (7.74 %) 5 (3.18 %)  
  95 % CI (4.47–7.56) (2.01–7.01) (5.37–10.11) (0.43–5.94)  
 Normal weight, n (%) 455 (49.78 %) 150 (56.39 %) 236 (48.07 %) 69 (43.95 %)  
  95 % CI (46.53–53.03) (50.42–62.36) (43.64–52.49) (36.17–51.73)  
 Overweight, n (%) 279 (30.53 %) 78 (29.32 %) 146 (29.74 %) 55 (35.03 %)  
  95 % CI (27.53–33.52) (23.84–34.8) (25.68–33.79) (27.56–42.51)  
 Obese, n (%) 121 (13.24 %) 24 (9.02 %) 70 (14.26 %) 27 (17.20 %)  
  95 % CI (11.04–15.44) (5.57–12.47) (11.16–17.36) (11.28–23.11)  
 Unknown, n (%) 4 (0.44 %) 2 (0.75 %) 1 (0.20 %) 1 (0.64 %)  
  95 % CI (0.01–0.87) (0.00–1.79) (0.00–0.60) (0.00–1.88)  
Years since CLBP presentation      <0.001
 Number of patients 808 232 435 141  
 Mean ± SD, years 9.09 ± 9.07 6.32 ± 7.61 10.91 ± 9.37 8.05 ± 9.10  
Age of IBP onset      <0.001
 Number of patients 908 264 488 156  
 Mean ± SD, years 28.8 ± 9.7 27.8 ± 7.3 27.0 ± 7.7 36.2 ± 14.2  
  1. Abbreviations: AS ankylosing spondylitis, BMI body mass index, CLBP chronic low back pain, CRF case report form, IBP inflammatory back pain, nr-axSpA nonradiographic axial spondyloarthritis
  2. Broad race categories (white vs. black vs. Asian vs. unknown) were created on the basis of physician-reported patient ethnicity: white = Indian, Indo-Aryan, Dravidian, Bengali, Arab, Iranian, white, Jewish, Azeri, Mestizo, Amerindian, Berber; black = black, mulatto, mulato, zambo, black African, colored; Asian = Han Chinese, non-Han Chinese, Taiwanese, Chinese, aborigine, Malay, indigenous, mongoloid, Asian; unknown = other or missing
  3. The p values represent the omnibus statistical comparison of percentages (or means) across IBP groups based on the chi-square (or F-test) values
  4. “Other IBP” refers to patients who did not meet the Assessment of SpondyloArthritis international Society classification criteria for axial spondyloarthritis