Evaluation of Direct Immunofluorescence Test for Diagnosis of Upper Respiratory Tract Infection by Chlamydia pneumoniae
Sopaporn Niemhom PhD*, Chanyuth Pongkun MSc**, Wimol Petkanchanapong PhD***, Chalermchai Chintrakarn MD****
Affiliation : * Department of Pathology, Faculty of Medicine Ramathibodi Hospital, Rajathevi, Bangkok ** Rajavithi Hospital, Department of Medical, Ministry of Public Health, Bangkok *** Department of Medical Science, National Institute of Health, Ministry of Public Health, Nonthaburi **** Department of Otorhinolaryngology, faculty of Medicine Ramathibodi Hospital, Rajathevi, Bangkok
Background : Chlamydia pneumoniae causes a variety of respiratory infections and is involved in cardio-
vascular diseases. Diagnosis of C. pneumoniae infection currently relies on antibody detection by
microimmunofluorescence (MIF), which has limited use, and is the retrospective diagnosis for acute infection.
Objective : Find an effective early diagnosis of acute upper respiratory infection, or use in combination with
MIF to accurately diagnose the infection by C. pneumoniae.
Material and Method: Direct immunofluorescence (DIF) was developed to detect C. pneumoniae in nasopha-
ryngeal specimens obtained from patients with upper respiratory tract infection, and normal individuals. IgM
and IgG antibodies against C. pneumoniae by MIF were determined for evaluation of the detected C.
pneumoniae and seroconversion.
Results : DIF gave positive results in 29 of 37 (78.4%) samples from 31 patients. Fifteen samples positive by
DIF illustrated antibody titers interpreted as acute C. pneumoniae infection, and eight DIF positive samples
showed antibody titers of chronic infection. Negative results by both DIF and MIF were found in two patients
and 23 of 25 by DIF but 20 of 25 by MIF in normal subjects. Five paired sera subsequently collected from three
of the 31 patients illustrated seroconversion 2-4 months after the primary specimen collection, which gave
positive results by DIF but negative for antibodies. Significant association was found between C. pneumoniae
detection by DIF and antibodies by MIF when analysis was done in the group of patients and normal subjects
(p < 0.001; Pearson chi-square test).
Conclusion : DIF could be an alternative assay for early diagnosis of C. pneumoniae infection, and may be
used in combination with MIF for accurate diagnosis of acute C. pneumoniae infection.
Keywords : Direct immunofluorescence, Chlamydia pneumoniae, upper respiratory infection, microimmuno- fluorescence, Chlamydia pneumoniae antibody
