Table 2

Predictors of WOMAC Pain scores during the crossover trial*

PredictorModel 1Model 2
Active treatment−1.78−1.82
 95% CI−3.66 to 0.11−3.05 to −0.60
 p Value0.060.004
Treatment, period 1 versus period 2−0.430.38
 95% CI−2.38 to 1.52−1.61 to 0.85
 p Value0.660.54
Carryover effect0.10
 95% CI−2.94 to 3.14
 p Value0.95
  • * Values for model predictors are β coefficients. For treatment as a predictor, a value of x means that active treatment was associated with an x lower score on the WOMAC Pain scale compared with control treatment. An unstructured correlation matrix for observations within subjects was used in generalised estimating equation fitting of the marginal model (model 1). Model 2 was conducted with exclusion of the differential carryover effect.

  • Tests whether treatment effects differed according to use in period 1 or period 2, constituting the differential carryover effect.

  • WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.