Related Experiment Video
Updated: Jul 31, 2026
High-throughput Detection Method for Influenza Virus
Published on: February 4, 2012
New criteria for immunofluorescence assay for Q fever diagnosis in Japan
1Laboratory of Rickettsia and Chlamydia, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-Ku, Tokyo 162-8640, Japan.
Abstract:
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 > or =1:128 and/or IgG titer of > or =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 < or =1:16 and an IgG titer of < or =1:32 by the IFA test were negative by both ELISA and WBA. In the proposed "equivocal area," with an IgM titer of > or =1:32 and < or =1:64 and/or an IgG titer of > or =1:64 and < or =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.
Insights
This study suggests using an "equivocal area" for Q fever diagnosis with the indirect immunofluorescent-antibody (IFA) test, rather than a single cutoff value. This approach improves accuracy by identifying samples needing further serological confirmation.
Area of Science:
- Medical Microbiology
- Immunoserology
- Infectious Diseases
Background:
- Q fever diagnosis relies on serological tests, with the indirect immunofluorescent-antibody (IFA) test being a common method.
- Establishing accurate cutoff values for serological tests is crucial to avoid misdiagnosis.
Purpose of the Study:
- To evaluate the optimal cutoff value for the indirect immunofluorescent-antibody (IFA) test in diagnosing Q fever in Japan.
- To determine if a single cutoff value is sufficient or if an "equivocal area" is necessary for accurate Q fever diagnosis.
Main Methods:
- Analysis of 346 serum samples: 16 from confirmed Q fever cases, 304 from Japanese pneumonia patients, and 26 negative controls.
- Comparison of IFA test results with enzyme-linked immunosorbent assay (ELISA) and Western blotting assay (WBA) for confirmation.
- Investigation of an "equivocal area" with intermediate IFA titers.
Main Results:
- A single cutoff value for the IFA test may lead to false-positive and false-negative Q fever diagnoses.
- An "equivocal area" (IgM: 1:32-1:64, IgG: 1:64-1:128) identified 9 samples requiring further testing.
- Within the equivocal area, 3 confirmed Q fever cases and 1 pneumonia case showed positive results by ELISA and WBA.
Conclusions:
- An "equivocal area" is recommended for the IFA test in Q fever diagnosis instead of a single cutoff value.
- Sera falling within the equivocal area necessitate additional serological assays for definitive confirmation.
- This approach enhances the reliability of Q fever serological diagnostics.
More Related Videos
07:27The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii
Published on: April 18, 2016
06:22Standardization of Transfer across Labs between Flow Cytometers for Detection of Lymphocytes in Japanese Encephalitis Vaccinated Children
Published on: February 10, 2023
