Open AccessNew Criteria for Immunofluorescence Assay for Q Fever Diagnosis in Japan
Author(s) -
Agus Setiyono,
Motohiko Ogawa,
Yan Cai,
Sawako Shiga,
Tadamitsu Kishimoto,
Ichiro Kurane
Publication year - 2005
Publication title -
journal of clinical microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.349
H-Index - 255
eISSN - 1070-633X
pISSN - 0095-1137
DOI - 10.1128/jcm.43.11.5555-5559.2005
Subject(s) - titer , serology , antibody , pneumonia , immunoglobulin m , indirect immunofluorescence , immunology , medicine , virology , immunofluorescence , immunoglobulin g
A study was made to evaluate the cutoff value of indirect immunofluorescent-antibody (IFA) test for Q fever diagnosis in Japan. We used 346 sera, including 16 from confirmed Q fever cases, 304 from Japanese pneumonia patients, and 26 from negative cases. Thirteen sera from the confirmed Q fever cases with an immunoglobulin M (IgM) titer of ≥1:128 and/or IgG titer of ≥1:256 by the IFA test were positive by both enzyme-linked immunosorbent assay (ELISA) and Western blotting assay (WBA), whereas 298 sera from pneumonia patients and 26 negative sera with an IgM titer of ≤1:16 and an IgG titer of ≤1:32 by the IFA test were negative by both ELISA and WBA. In the proposed “equivocal area,” with an IgM titer of ≥1:32 and ≤1:64 and/or an IgG titer of ≥1:64 and ≤1:128, we found 9 sera, 3 from confirmed Q fever cases and 6 from Japanese pneumonia patients, by the IFA test. Three sera from the confirmed Q fever cases and one of the sera from pneumonia patients were IgM and/or IgG positive by both ELISA and WBA. These results suggest that a single cutoff value for the IFA test may cause false-positive and false-negative results. In conclusion, this study showed that an “equivocal area” should be used for the IFA test rather than a single cutoff value and that sera in the equivocal area should be tested by additional serological assays for confirmation.