Table 3. Prognostic factors: multivariate analysis of Cox proportional hazards model.

Variable	risk ratio	95% CI	p-value
Cause of empyema
Exacerbation of interstitial pneumonia	0	0.00	0.999
Bronchial stump fistula	0.371	0.064–2.165	0.558
Pre-operative complication
Administration of steroid	0.188	0.008–4.311	0.296
Interstitial pneumonia	1.844	0.00	1
Histology
Squamous cell ca.	0.325	0.053–1.982	0.223
Microbiology
Non-fermenting Gram(-) bacilli	0	0.00	0.999