Table 3

Final result of multivariate analysis of parameters used to predict mortality as part of Cox proportional hazards method for all cause mortality (n = 170 total, deaths = 15) and respiratory mortality (n = 164, deaths = 9)

Bp valueHazard ratio
Most significant parameter from univariate analysis entered at step 1, then parameters that remain significant entered in subsequent steps. All parameters included as in univariate analysis in table 2; only significant covariates shown at each step. B = estimated coefficient; significance shown (p value). Hazard ratio = eB, the predicted multiplicative change in the hazard for a unit increase in the predictor (>1 indicates that, as the predictor increases, the hazard, i.e. mortality, also increases); 95% confidence intervals shown in parentheses. In this model the hazard ratios for the significant covariates shown at each step are additive.
All cause mortality:
Step 1: Upper expiratory scan0.0390.0011.039 (1.015 to 1.064)
Step 2 (final): Upper expiratory scan0.0370.0031.038 (1.012 to 1.064)
Age0.0590.0351.061 (1.004 to 1.121)
Respiratory mortality:
Step 1: Upper expiratory scan0.0530.0011.054 (1.022 to 1.087)
Step 2: Upper expiratory scan0.0540.0011.056 (1.021 to 1.091)
Age0.1020.0151.100 (1.018 to 1.187)
Step 3: Upper expiratory scan0.0310.1611.031 (0.988 to 1.076)
Age0.1020.0161.108 (1.019 to 1.204)
Lower expiratory scan0.0840.0371.088 (1.005 to 1.177)
Step 4 (final): Lower expiratory scan0.0990.0061.105 (1.028 to 1.186)
Age0.0970.0201.102 (1.015 to 1.196)