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