Microbiological investigations and diagnostic criteria
| Diagnostic criteria | |||||
|---|---|---|---|---|---|
| Specimen | Agent/antigen | Assay | Definite | Probable | Possible |
| Serum | Respiratory viruses/antibodies | CF | Acute titre ⩾1/128 or a fourfold rise | Convalescent titre ⩾1/128 | — |
| Coxiella burnetti/antibodies | CF | Acute titre ⩾1/128 or a fourfold rise | Convalescent titre ⩾1/128 | — | |
| Mycoplasma pneumoniae/antibodies | CF | Acute titre ⩾1/128 or a fourfold rise | Convalescent titre ⩾1/128 | — | |
| Cytomegalovirus | CF | Acute titre ⩾1/128 or a fourfold rise | Convalescent titre ⩾1/128 | — | |
| Chlamydia psittaci | CF | Acute titre ⩾1/128 or a fourfold rise | Convalescent titre ⩾1/128 | — | |
| Group A streptococcus | ASOT | >2 dilutional increments | — | — | |
| S pneumoniae/antipneumolysin antibodies | ELISA | Twofold rise in titre | — | — | |
| Cold agglutinins | ⩾1:32 | — | — | ||
| Bacteria | Culture | Growth | — | — | |
| NPS/sputum | Respiratory viruses | IF | Positive | — | — |
| Bacteria | Culture | — | Growth | — | |
| S pneumoniae/CPS | CIE | — | Positive | — | |
| Pneumolysin antigen | Western blot | — | Positive | — | |
| Pneumolysin gene | PCR | — | — | Positive | |
| N/Tswabs | Respiratory viruses | Culture | Growth | — | — |
| Bacteria | Culture | — | — | Growth | |
| Urine | S pneumoniae | CIE | Positive | — | — |
Respiratory viruses tested were: RSV, influenza A+B, parainfluenza 1, 2, and 3 virus, and adenovirus.
ASOT, antistreptolysin O titre; ELISA, enzyme linked immunosorbent assay; IF, immunofluorescence; CPS, capsular polysaccharide antigen; CIE, countercurrent immunoelectrophoresis; PCR, polymerase chain reaction; CF, complement fixation.