Table 4– Multivariate logistic regression analysis of hypothesised risk factors for pneumococcal para-pneumonic effusion (PPE), with untyped pneumococcal community-acquired pneumonia (CAP) as a reference group

	OR (95% CI)	p-value
Age <60 years	2.7 (1.5–4.9)	0.001
PPE-related serotype^#	2.5 (1.3–4.8)	0.007
Other serotype^¶	1.1 (0.6–2.0)	0.766
Creatinine >130 μmol·L⁻¹	1.1 (0.6–2.0)	0.674
CRP >100 mg·L⁻¹	1.0 (0.5–1.7)	0.897
COPD	1.6 (0.8–3.0)	0.189
Chronic liver disease	0.7 (0.1–3.7)	0.695
Sodium <130 mmol·L⁻¹	1.7 (0.8–3.6)	0.141
Platelets >400×10⁹ L⁻¹	1.9 (0.7–4.6)	0.207
Tachycardia >100 beats·min⁻¹	0.5 (0.3–0.9)	0.012
Leukocytes >15 000 cells·mm⁻³	0.7 (0.4–1.2)	0.160

Bold type represents significance at p<0.05. CRP: C-reactive protein; COPD: chronic obstructive pulmonary disease. ^#: 1, 3, 7F and 19A; ^¶: all other detectable serotypes, excluding the untyped group.