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Table 2 Risk estimates from alternative models for associations between hospital and surgeon volume and prolonged LOS

From: Factors predicting hospital length-of-stay after radical prostatectomy: a population-based study

Model

Variable (comparison)

Adjusted OR1

95% CI2

p-value

Model 1 (primary analysis): Hospital and surgeon volume both fitted in model (without interaction term)1

Hospital volume: (higher vs lower)

0.34

0.26-0.45

 

Surgeon volume: (higher vs lower)

0.55

0.42-0.71

 

Model 2: Surgeon volume omitted

Hospital volume: (higher vs lower)

0.37

0.29-0.48

p < 0.0013

Model 3: Hospital volume omitted

Surgeon volume: (higher vs lower)

0.63

0.49-0.81

p < 0.0013

Model 4: Hospital and surgeon volume fitted with an interaction term4

Hospital volume main effect: (higher vs lower)

0.28

0.20-0.40

p = 0.1054

Surgeon volume main effect: (higher vs lower)

0.46

0.33-0.64

 

Interaction effect

1.55

0.92-2.65

 
  1. 1Final multivariate model as shown in Table 1, 295% confidence intervals, 3p-value for likelihood ratio tests compared to baseline model (model 1), 4Model 4 is the baseline model with the addition of an interaction term; the p value is for the interaction term.