Table 3.

Final prediction model to predict exacerbations in COPD patients

	ORa	95% CIa
Previous exacerbations	5.07	2.55–10.07
FEV1, %predicted (Or per 5%)b	0.95	0.88–1.03
Pack years of smoking (2log transformed)c	1.16	1.01–1.35
History of vascular disease	1.92	0.89–4.12

Notes:

^aAfter adjustment for overfitting by shrinkage (shrinkage factor =0.90).

^bOR for each interval change of 5%;

^cdoubling of the number of log-transformed pack years results in 1.16 times higher OR. Risk of COPD exacerbation within the next 24 months = 1/(1 + exp − (−1.33 + 1.62 × previous exacerbation − 0.05 × FEV₁ (% predicted, per 5% interval change) + 0.15 × 2log(pack years) + 0.65 × history vascular disease)). Examples: a male person aged 73 years with a history of exacerbations in the previous year, FEV₁ of 32.9 as %predicted, a history of 38 pack years of smoking, and prior stroke. His chance of an exacerbation in the next 2 years is: 1/(1 + exp − (−1.33 + 1.62 − 0.05 × (32.9/5) + 0.15 × 2log(38) + 0.65)) = 0.79 = 79%. A female person aged 77 years, without any exacerbations in the previous year, FEV₁ of 77.7 as %predicted, who never smoked, and who does not have a history of stroke or peripheral artery disease. Her chance of an exacerbation in the next 2 years is: 1/(1 + exp − (−1.33 + 0 − 0.05 × (77.7/5) + 0.15 × 2log(0) + 0)) = 0.09 = 9%.

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; OR, odds ratio.