Table 5. Risk Predictors for Bronchiolitis or Emphysema Detected on CT Scans.

Model	Variables	Crude OR (95% CI)	ROC (95% CI)	Multivariate OR (95% CI)*	Incremental ROC (95%)†	p‡
1	Current Smoker	3.86 (3.08,4.85)	0.656 (0.631, 0.680)	3.48 (2.58, 4.71)	0.656 (0.631, 0.680)	–
2	WBC (per 103 cells/mm3 increase)	1.23 (1.15, 1.32)	0.614 (0.579, 0.648)	1.13 (1.05, 1.22)	0.689 (0.656, 0.721)	0.0004
3	Intravenous Drug Use	2.65 (2.09, 3.37)	0.595 (0.573, 0.618)	2.14 (1.56, 2.94)	0.713 (0.681, 0.744)	0.0037
4	Age (per 10 year increase)	1.42 (1.24, 1.64)	0.577 (0.548, 0.606)	1.63 (1.35, 1.99)	0.730 (0.699, 0.760)	0.0360
5	BMI (per 5 kg/m2 decrease)	1.38 (1.20, 1.60)	0.568 (0.538, 0.598)	1.43 (1.18, 1.74)	0.733 (0.703, 0.764)	0.3145
6	Men	1.68 (1.33, 2.11)	0.552 (0.529, 0.576)	2.03 (1.46, 2.81)	0.743 (0.713, 0.773)	0.0679

Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio; ROC, receiver operating characteristics; WBC, white blood cell;

*adjusted for all the variables listed in this table in a multivariate logistic regression model (see Methods for detail).

^†Incremental ROC represents area under the curve obtained by adding the previous row variable to the current row variable in a multivariate logistic regression model (see Methods for detail). For example, model 2 incremental ROC and p values are obtained by comparing a logic regression model that contains WBC and current smoker variables to that which contains only current smoker variable (i.e. model 1).

^‡p value is obtained by comparing the incremental ROC value of the current row to the previous row ROC value.