Serum lactase dehydrogenase (LDH) level was significantly lower in the CPPE/empyema group (210±125 IU/L) than in the PPE group (254±130 IU/L; p = 0.033) (Table 2), whereas serum white blood cell (WBC) count and C-reactive protein (CRP) level were not significantly different between groups (WBC: 13,400±6,540/μL vs. 14,800±13,600/μL; CRP: 20.4±18.1 mg/dL vs. 18.4±11.0 mg/dL). Here, CRP is linked to empyema.