Adjusted ORs and regression coefficients (β) for risk factors included in the final risk model
| OR* | (95% CI) | β | (95% CI) | |
|---|---|---|---|---|
| Smoking status | ||||
| Never | 1 | 0 | ||
| Former | 4.72 | (4.35 to 5.12) | 1.55 | (1.47 to 1.63) |
| Current | 11.7 | (10.7 to 12.7) | 2.46 | (2.37 to 2.54) |
| Missing | 2.44 | (2.16 to 2.76) | 0.89 | (0.77 to 1.02) |
| Asthma | 2.11 | (1.93 to 2.31) | 0.75 | (0.66 to 0.84) |
| LRTI† | ||||
| 0 | 1 | 0 | ||
| 1 | 2.57 | (2.36 to 2.81) | 0.94 | (0.86 to 1.03) |
| >1 | 4.29 | (3.83 to 4.80) | 1.46 | (1.34 to 1.57) |
| Salbutamol† | 6.91 | (6.33 to 7.55) | 1.93 | (1.85 to 2.02) |
As this model was developed using case-control data, the intercept term is not applicable and has therefore not been presented.
*Estimated using a multivariable conditional logistic regression model.
†Within 3 years of COPD diagnosis or equivalent matched time point for controls.
Risk score=(former smoker×1.55)+(current smoker×2.46)+(unknown smoking status×0.89)+(asthma×0.75)+(1 episode of LRTI×0.94)+(>1 episode of LRTI×1.46)+(salbutamol×1.93).
NB. Each variable can either take the value 0 (not present) or 1 (present).
For example, A former smoker with a history of asthma who presented with more than one lower respiratory tract infection in the past 3 years, and received salbutamol in the past 3 years would have the following risk score:
(1×1.55)+(0×2.46)+(0×0.89)+((1×0.75)+(0×0.94)+(1×1.46)+(1×1.93)=5.69.
COPD, chronic obstructive pulmonary disease; LRTI, lower respiratory tract infection.