The Journal of Medical Microbiology, Vol 47, Issue 4 325-328, Copyright © 1998 by Society for General Microbiology
Evaluation of clinical usefulness of the microplate agglutination test for serological diagnosis of legionella pneumonia
K. Tateda, H. Murakami, Y. Ishii, N. Furuya, T. Matsumoto and K. Yamaguchi
Department of Microbiology, Toho University School of Medicine, Tokyo, Japan. kazu@sirius.med.toho-u.ac.jp
Recently, a microplate agglutination test (MPAT) was established for the
serological diagnosis of legionella pneumonia. To evaluate its usefulness,
this study examined antibody titres in 121 serum samples serially obtained
from 40 patients with pneumonia, including 17 cases of confirmed legionella
pneumonia. Six of the 17 proven cases became serologically positive within
4 weeks of the onset of pneumonia as assayed by MPAT (cut-off value:
four-fold rise to > or = 128 in paired sera or > or = 256 in a single
serum specimen), whereas the remaining 11 cases were serologically negative
despite serial examination. Four proven cases who were treated with
corticosteroids in the acute phase had antibody titres <8 during the
first 4 weeks of infection, after which one case showed an elevation in
antibody titre for the first time, 13 weeks after the onset of disease. In
contrast, all non-proven cases had antibody titres of < or = 64, and
only one case developed a four-fold or greater rise in titre. These results
indicate that MPAT is a useful method for the laboratory diagnosis of
suspected legionella pneumonia, although several false-negative cases were
observed. This suggests that the previously established MPAT criteria may
require modification, possibly to slightly lower values. These data also
indicate that serial examination over the first month of infection may be
necessary for serodiagnosis of legionella pneumonia, especially in patients
treated with corticosteroids.
