Characteristics of participants (n=126)
| Age, years, median (IQR) | 56.0 (38.7–71.4) |
| Male, n (%) | 89 (71) |
| Duration of symptoms prior to presentation, median (IQR) | 14 (7–28) |
| Co-morbidity, n (%) | 86 (68) |
| Chronic respiratory disease | 15 (12) |
| Excess alcohol consumption | 17 (14) |
| Diabetes mellitus | 13 (10) |
| Patients with neutropenia on admission blood tests | 0 (0) |
| Pleural fluid characteristics | |
| Visibly purulent, n (%) | 104 (83) |
| Positive standard microbiology, n (%) | 69 (55) |
| Streptococcus pneumoniae | 12 |
| Anginosus group of streptococci | 13 |
| Other streptococci | 5 |
| Staphylococcus aureus | 9 |
| Anaerobic or mixed aerobic/anaerobic infection | 16 |
| Mixed aerobic bacteria | 8 |
| Gram-negative bacteria | 6 |
| pH in patients without frankly purulent fluid, median (IQR) | 6.9 (6.7–7.1) |
| Glucose (mg/dl), median (IQR) | 18 (11–61) |
| Lactate dehydrogenase (IU/l), median (IQR) | 6000 (1629–20000) |
| Patient laboratory characteristics | |
| Total white cell count (×109/l), median (IQR) | 14.7 (10.3–22.0) |
| C-reactive protein (mg/l), median (IQR) | 187 (83–271) |
| Albumin (g/l), median (IQR) | 27 (22–31) |