Table 2. Laboratory investigations and diagnostic criteria of likely causative pathogens of pneumonia.

Sample	Pathogen/antigen	Tests	Interpretation
Serum	Respiratory viruses	Complement fixation	Acute titre ≥1/128 or 4-foldrise between paired sera
	Atypical bacteria
	Mycoplasma	IgM antibody	Positive
	Group AStreptococcus	Antistreptolysin O titre (IU/mL)	Acute 2-fold rise or 4-foldrise between paired sera
Blood	Bacteria	Culture	Growth
	Streptococcus pneumoniae	Real-time PCR	Positive
Nasopharyngealsecretions/sputum	Respiratoryviruses	Real-time PCR	Positive
Tracheobronchial secretions(collected via endotrachealtube or bronchoalveolar lavage)	Respiratoryviruses	Real-time PCR	Positive
	Bacteria	Culture/Real-time PCR	Growth/Positive
Pleural fluids	Bacteria	Culture	Growth
	Pneumococcalantigen	ELISA1	Positive
	Streptococcus pneumoniae	Real-time PCR	Positive

¹ELISA, enzyme-linked immunosorbent assay.