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Table 1 Prevalence rates of demographic and clinical characteristics in subgroups of MRI findings

From: Identification of subgroups of inflammatory and degenerative MRI findings in the spine and sacroiliac joints: a latent class analysis of 1037 patients with persistent low back pain

  All Subgroup 1: No or few findings Subgroup 2: Mild spinal degeneration Subgroup 3: Moderate/severe spinal degeneration Subgroup 4: Moderate/severe spinal degeneration and mild SIJ findings Subgroup 5: Mild spinal degeneration and moderate/severe SIJ findings P value, significant pair-wise comparisons
  (n = 1037) (n = 116) (n = 540) (n = 229) (n = 68) (n = 84)  
Age (years), median (IQR) 33 (27–37) 28 (23–33) 32 (26–36) 36 (32–39) 34 (30–37) 29 (25–33) <0.05 for all comparisons except 1 vs 5 and 3 vs 4
Women,% (95 % CI) 54 (51–57) 76 (68–84) 51 (47–55) 40 (33–46) 68 (56–79) 68 (58–78) < 0.01 for 2 vs all and 3 vs all
Regular employment, % (95 % CI) 70 (68–73) 67 (58–76) 71 (67–75) 76 (71–82) 56 (43–68) 67 (56–78) < 0.05 for 2 vs 4 and 3 vs 4
Being overweight (BMI > 25), % (95 % CI) 53 (50–57) 36 (26–46) 51 (47–56) 63 (56–69) 67 (55–79) 53 (41–65) < 0.05 for 1 vs all, 2 vs 3 and 2 vs 4
Previous LBP episode(s), % (95 % CI) 74 (72–77) 58 (48–67) 73 (69–76) 83 (79–88) 81 (71–91) 79 (70–89) < 0.01 for 1 vs all and 2 vs 3
Activity limitation (RMDQ), median (IQR) 57 (39–74) 48 (35–74) 57 (39–74) 57 (39–74) 65 (48–78) 65 (48–78) < 0.05 for 1 vs 4, 1 vs 5, 2 vs 4, 2 vs 5, 3 vs 4 and 3 vs 5
hsCRP, median (IQR) 1 (0–3) 1 (0–3) 1 (0–3) 1 (0–3) 2 (1–5) 3 (0–6) < 0.05 for 1 vs 4, 1 vs 5, 2 vs 4, 2 vs 5, 3 vs 4 and 3 vs 5
HLA-B27-positive, % (95 % CI) 10 (9–12) 12 (6–18) 7 (5–10) 6 (3–9) 12 (4–20) 40 (29–50) < 0.05 for 5 vs all, 1 vs 3 and 2 vs 4
  1. Only variables with a statistically significant group difference (P < 0.05) were included in the above pair-wise comparison, n varies due to missing values
  2. MRI magnetic resonance imaging, IQR interquartile range, CI confidence interval, BMI body mass index, LBP low back pain, RMDQ Roland Morris Disability Questionnaire (calculated as a proportional score (0 % = no activity limitation; 100 % = maximum activity limitation), hsCRP high-sensitivity C-reactive protein, HLA human leukocyte antigen