Table 3. Baseline characteristics of the five clusters of low back- related leg pain patients.
| Socio-demographics Denominator a |
Cluster 1 Referred leg pain n=104 |
Cluster 2 Mild sciatica n=122 |
Cluster 3 Moderate sciatica n=188 |
Cluster 4 Severe sciatica n=69 |
Cluster 5 Atypical sciatica n=126 |
p value Δ |
|---|---|---|---|---|---|---|
| Age (years) mean (SD) | 47.2 (13.8) | 50.4 (13.3) | 50.9 (14.4) | 49.2 (12.7) | 51.9 (14.1) | 0.111 |
| Age category 65+ | 13 (12.5) | 17 (13.9) | 33 (17.6) | 7 (10.1) | 22 (17.5) | 0.238 |
| Gender, Female | 76 (73.1) | 72 (59.0) | 113 (60.1) | 42 (60.9) | 80 (63.5) | 0.187 |
| Current smoker | 27 (26.0) | 29 (23.8) | 52 (27.7) | 30 (43.5) | 56 (44.4) | <0.001 |
| BMI (607) category: | 31 (29.8) | 49 (40.5) | 78 (41.5) | 36 (52.2) | 54 (43.2) | 0.056 |
| Obese/Morbidly obese | ||||||
| Socioeconomic status: Manual | 41 (39.4) | 43 (36.1) | 85 (46.4) | 36 (55.4) | 78 (63.9) | <0.001 |
| occupation (593) | ||||||
| Self-certified time off work (363) | 25 (35.7) | 20 (25.6) | 42 (35.0) | 11 (29.7) | 8 (13.8) | 0.032 |
| or current sick note (365) | 22 (31.4) | 16 (20.3) | 34 (28.3) | 14 (37.8) | 14 (16.2) | 0.279 |
| Back pain duration (607) >6 wks | 64 (61.5) | 72 (59.0) | 117 (62.6) | 47 (68.1) | 89 (71.2) | 0.279 |
| Leg pain duration (583) > 6wks | 50 (50.5) | 52 (45.2) | 105 (57.7) | 38 (57.6) | 87 (71.9) | 0.001 |
| > 3 months | 31 (31.3) | 24 (20.9) | 69 (37.9) | 20 (30.3) | 68 (56.2) | <0.001 |
| >12 months | 15 (15.2) | 10 (8.7) | 24 (13.2) | 3 (4.5) | 29 (24.0) | <0.001 |
| Back pain intensity, mean (SD) | 5.3 (1.7) | 3.4 (1.4) | 5.0 (1.5) | 8.0 (1.3) | 7.5 (1.4) | <0.001 |
| Leg pain intensity, mean (SD) | 3.1 (1.4) | 2.6 (1.2) | 5.5 (1.3) | 8.5 (1.1) | 7.2 (1.4) | <0.001 |
| RMDQ disability score (0-23) | 11.5 (5.6) | 8.6 (5.0) | 12.8 (4.7) | 16.7 (5.1) | 15.1 (5.5) | <0.001 |
| mean (SD) (607) | ||||||
| Sciatica Bothersomeness Index | 11.1 (4.9) | 10.0 (4.4) | 14.7 (4.0) | 19.8 (3.5) | 17.2 (4.4) | <0.001 |
| (0-24)mean (SD) (582) | ||||||
| S-LANSS, possible neuropathic | 37 (35.6) | 44 (36.4) | 100 (53.2) | 45 (66.2) | 67 (53.6) | <0.001 |
| pain (≥12) (606) | ||||||
| STarT Back subgroup (589) | <0.001 | |||||
| Low risk | 17 (17.0) | 44 (37.0) | 16 (13.4) | 0 (0.0) | 5 (4.0) | |
| Medium risk | 52 (52.0) | 59 (49.6) | 105 (58.0) | 20 (30.8) | 40 (32.3) | |
| High risk | 31 (31.0) | 16 (8.8) | 60 (33.1) | 45 (69.2) | 79 (63.7) | |
| Widespread pain b (592) | 50 (49.9) | 48 (40.7) | 72 (38.9) | 15 (22.4) | 65 (54.2) | <0.001 |
| HADS Anxiety (607)subscale | ||||||
| Probable c | 32 (31.1) | 20 (16.4) | 34 (18.2) | 33 (47.8) | 52 (41.3) | <0.001 |
| HADS Depression subscale | ||||||
| Probable c | 12 (11.5) | 9 (7.4) | 21 (11.2) | 26 (37.7) | 30 (23.8) | <0.001 |
| Pain self-efficacy score (0-60), | 37.6 (12.4) | 42.9 (12.5) | 34.7 (12.3) | 22.5 (15.6) | 28.4 (14.3) | <0.001 |
| mean (SD) (593) | ||||||
| EQ—5D-3L summary index (590) | 0.54 (0.3) | 0.66 (0.2) | 0.48 (0.3) | 0.13 (0.3) | 0.29 (0.3) | <0.001 |
| Co-morbidities | ||||||
| Two or more other health | 16 (15.4) | 15 (12.3) | 21 (11.2) | 5 (7.2) | 23 (18.3) | 0.139 |
| problems | ||||||
| General Health (608) | ||||||
| Fair/poor | 38 (36.5) | 31 (25.5) | 59 (31.4) | 32 (47.1) | 62 (49.2) | <0.001 |
| Sleep Disturbance (yes) d | 69 (66.3) | 73 (59.8) | 133 (70.7) | 61 (88.4) | 92 (73.0) | 0.001 |
| Clinical diagnosis sciatica | 20 (19.2) | 99 (81.1) | 175 (93.1) | 69 (100.0) | 89 (70.6) | <0.001 |
| Clinician confidence in diagnosis | 72 (69.2) | 75 (61.4) | 156 (83.0) | 63 (91.3) | 70 (55.6) | <0.001 |
| ≥80% | ||||||
| MRI (554) | ||||||
| Clear or possible nerve root | 25 (26.3) | 56 (50.5) | 106 (63.1) | 57 (89.1) | 53 (45.7) | <0.001 |
| compression | ||||||
| Disc prolapse | 17 (68.0) | 47 (83.9) | 84 (79.2) | 49 (86.0) | 33 (62.3) | |
| Stenosis | 6 (24.0) | 7 (12.5) | 19 (17.9) | 7 (12.3) | 16 (30.2) | |
| Other e | 2 (8.0) | 2 (3.6) | 3 (2.8) | 1 (1.8) | 4 (7.5) | |
SD, standard deviation; BMI, body mass index; RMDQ, Roland Morris Disability Questionnaire; s-LANSS, self-report Leeds Assessment of Neuropathic Symptoms and Signs; HADS, Hospital Anxiety and Depression Scale; EQ-5D-3L EuroQoL; MRI, magnetic resonance imaging
All figures are frequencies (percentages) unless otherwise stated as mean (SD).
Significance p-value (α=0.05) for the difference between patients in the five latent clusters on ANOVA for continuous variables (Kruskill Wallis for variables BMI, HADS(depression) and EQ-5D) and Chi squared test for categorical variables (Fisher’s exact test for variable socioeconomic cluster and general health).
Denominator varies for some participants due to missing data or non-applicable cases All figures are frequencies (percentages) unless otherwise stated as mean (SD)
Widespread pain derived from the shaded body manikin (defined as pain present above and below the waist in the right and left hand sides of the body and in the axial skeleton).
Score of ≥ 11 indicative of probable depression/anxiety
Question on back and/or leg pain associated sleep disturbance was asked during the clinical assessment.
Other MRI diagnoses (n= 11) included spondylolisthesis, epidural lipomatosis, synovial cyst, osteophyte