Cox proportional hazards analysis of survival in 584 patients with cystic fibrosis: univariate analysis
| Parameter | χ2value | p value | RR (95% CI) |
| FEV1 | 137.0 | <0.0001 | 0.999 (0.998 to 0.999) |
| % predicted FEV1 | 143.3 | <0.0001 | 0.945 (0.934 to 0.956) |
| % ideal weight | 62.0 | <0.0001 | 0.955 (0.944 to 0.967) |
| Pao 2 | 21.7 | <0.0001 | 0.730 (0.637 to 0.838) |
| Paco 2 | 4.0 | 0.04 | 1.280 (1.009 to 1.622) |
| Age (years) | 0.7 | 0.406 | 1.010 (0.986 to 1.034) |
| Female sex | 1.2 | 0.280 | 1.203 (0.860 to 1.684) |
FEV1 = forced expiratory volume in one second; Pao 2= arterial oxygen tension ; Paco 2 = arterial carbon dioxide tension; % ideal weight = weight as percentage of the predicted ideal weight.