Table 2 Diagnostic tests for Legionnaires’ disease in 103 outbreak patients
From: Characterization of the extent of a large outbreak of Legionnaires’ disease by serological assays
Case definition | Laboratory test | No. positive/no. tested (%) | Additional (cumulative) no. of LD-cases | Comments |
|---|---|---|---|---|
Confirmed LD (direct demonstration of Lp 1 infection) | Positive Lp 1 UAT* | 52/99 (53) | 52 | |
Culture of Lp 1 (sputum)* | 4/30 (13) | 1 (53) | Pos. UAT : 3 | |
Neg UAT: 1 | ||||
Culture of Lp 1 (lung tissue)* | 6/7 (86) | 3 (56) | Pos UAT: 3 | |
Neg UAT: 2 | ||||
UAT not done: 1 | ||||
Positive PCR | 8/25 (32) | 0 (56) | Sputum: 5/22 | |
Lung tissue: 3/3 | ||||
Confirmed LD** (serology) | ≥4-fold titre change in IFA | 40/84 (48) | 25 (81) | 13 patients had ≥4-fold titre change in IFA, but no seroconversion in ELISA. |
IgM/IgG seroconversion in ELISA | 30/84 (36) | 6 (87) | ||
Probable LD (single high or high standing antibody level) | IFA-titre ≥128 | 68/92 (74) | 9 (96) | |
ELISA IgM ≥120 U/ml and/or IgG ≥50 U/ml | 59/92 (64) | 1 (97) | ||
Probable LD (ELISA ratio ≥1.5) | ELISA IgM ratio ≥1.5 and/or IgG ratio ≥1.5 | 75/84 (89) | 6 (103) |