Investigations

• blood culture ^c
• sputum Gram stain ^d and culture ^c

Note:

• Only 70% of patients were able to produce a purulent sputum sample. ^d
• Routine microbial investigations often fail to detect a causative agent, (74%: 95% CI: 65% to 82%) ^c and even with extensive screening a third of patients will have no specific pathogen identified (34%: 95% CI: 29% to 38%) ^c
• Few patients have antibiotics changed on the basis of microbial results (7.6%: 95% CI: 2.5% to 13%) ^c

Specimen culture in pneumonia often fails to detect a causative organism

specimen c	organism cultured
sputum smear	52% (43% to 61%)
sputum culture	35% (26% to 43%)
blood culture	11% (6.3% to 16%)

• Bacteraemia increases the risk of dying in the next month ^b

Bacteraemia increases the risk of dying

Patient	Prognostic Factor	Outcome	CER	OR (95% CI)	NNF+ (95% CI)
community-acquired pneumonia b	bacteraemia independent	death at uncertain duration	14%	2.8 (2.3 to 3.6)	7 (5 to 10)