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TABLE 3
—Estimated Effectsa (With 95% Confidence Intervals [CIs]) of Assigned Provider Group and Selected Covariates on Satisfaction Score: Results of Fitting 3 Mixed Linear Models (n = 672)
| Predictor (Contrast)b | Model 1 | Model 2 | Model 3 |
| Assigned provider group (chiropractic vs medical)c | 5.2 (2.9, 7.5) | 3.1 (1.6, 4.7) | 2.5 (0.7, 4.2) |
| Improvement in Roland-Morris Disability Questionnaire score (5 points) | 0.5 (–0.1, 1.2) | 0.3 (–0.3, 0.8) | 0.1 (–0.4, 0.7) |
| Improvement in average pain (1 point) | 0.6 (0.3, 1.0) | 0.5 (0.2, 0.8) | 0.6 (0.3, 0.8) |
| Baseline low back pain disability score (5 points) | –0.4 (–0.9, 0.2) | –0.3 (–0.7, 0.2) | –0.2 (–0.7, 0.3) |
| Average pain at baseline (1 point) | –0.6 (–1.0, –0.3) | –0.6 (–0.8, –0.3) | –0.6 (–0.9, –0.4) |
| Explanation of treatment (yes vs no) | . . . | 3.5 (2.6, 4.5) | 3.3 (2.4, 4.3) |
| Self-care advice | |||
| (2–3 vs 0–1 items) | . . . | 3.6 (2.7, 4.5) | 3.2 (2.3, 4.1) |
| (≥ 4 vs 0–1 items) | . . . | 6.6 (5.4, 7.8) | 6.1 (4.9, 7.3) |
| Confidence in treatment (2 points)d | . . . | . . . | 0.3 (0.1, 0.4) |
| Past benefit from assigned treatment (yes vs no) | . . . | . . . | 0.1 (–0.8, 0.9) |
| Total co-payments over 4-week period ($10) | . . . | . . . | 0.1 (–0.3, 0.4) |
| Average visit length (10 min) | . . . | . . . | 1.2 (0.7, 1.6) |
| Number of low back pain visits to provider (1 visit) | . . . | . . . | 0.5 (0.1, 0.9) |
| Baseline SF-36 mental health score (10 points) | . . . | . . . | 0.2 (–0.1, 0.4) |
| Education | |||
| Some college or vocational vs no college | . . . | . . . | 0.7 (–0.3, 1.6) |
| College degree vs no college | . . . | . . . | 0.3 (–0.7, 1.4) |
| Sex (male vs female) | . . . | . . . | 0.6 (–0.2, 1.3) |
| Percentage of total variation in satisfaction explained by model | 25 | 44 | 47 |
aThe estimated effect of a covariate is the adjusted difference in mean satisfaction score attributable to that covariate.
bThe contrast is the difference in values of the covariate for which the effect was estimated.
cThe unadjusted difference in mean satisfaction score between chiropractic and medical patients is 5.5 (95% CI = 4.5, 6.5).
dConfidence in treatment was measured on a 0–10 scale (see text).