Table 2.
Diagnosis of Legionnaires' disease
| Test | Time | Samplea | Sensitivity (%) | Specificity (%) | Comment |
|---|---|---|---|---|---|
| Culture | 3–7 d | LRT | <10–80 | 100 | Detects all strains |
| DFA stain | <4 h | LRT | 25–70 | >95 | Technically demanding |
| Urine antigen | <1 h | Urine | 70–90 | >99 | Detects only L pneumophila serogroup 1 |
| PCR | <4 h | LRT | 80–100 | >90 | Detects L pneumoniae (all serogroups) |
Abbreviations: DFA, direct immunofluorescent antibody; LRT, lower respiratory tract specimen; NPS, nasopharyngeal swab.
Adapted from Murdoch DR. Diagnosis of Legionella infection. Clin Infect Dis 2003;36:64.
a
Expectorated sputum, bronchoscopic aspirate, nasotracheal suction specimen.