Age specific prevalence of antibodies against Chlamydia pneumoniae in Iceland
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Published on: October 24, 2013
S Einarsson1, H K Sigurdsson, S D Magnusdottir
1University of Iceland Medical School, Reykjavik.
Insights
Chlamydia pneumoniae infections are common in Iceland, affecting over half the population. Antibody levels increase with age, and rheumatoid factor can cause false positive IgM test results.
Area of Science:
- Infectious Diseases
- Immunology
- Epidemiology
Background:
- Chlamydia pneumoniae is an emerging pathogen causing respiratory infections.
- Understanding its prevalence is crucial for public health in Iceland.
Purpose of the Study:
- To determine the prevalence of Chlamydia pneumoniae infection in Iceland.
- To analyze age- and gender-specific prevalence and identify potential confounding factors in antibody testing.
Main Methods:
- Serum samples from 1020 individuals aged 0-99 years were analyzed.
- Microimmunofluorescence assay was used to detect IgG and IgM antibodies.
- Rheumatoid factor testing and absorption were performed to validate IgM results.
Main Results:
- Overall IgG antibody prevalence was 53%, with significant age-related increases up to age 70.
- No significant seasonal or gender differences were observed for IgG prevalence.
- 34 samples were initially IgM positive, but 12 were false positives due to rheumatoid factor.
Conclusions:
- Chlamydia pneumoniae infection is highly prevalent in Iceland, comparable to neighboring countries.
- Age is a significant factor in C. pneumoniae seroprevalence.
- Rheumatoid factor interference necessitates careful interpretation of IgM results.
Abstract:
Chlamydia pneumoniae is a newly recognized common cause of respiratory tract infections. The aim of this study was to examine its prevalence in Iceland. The study was based on 1020 serum samples from individuals 0-99 years old. The samples were divided into 10-year age groups. IgG and IgM antibodies were determined with microimmunofluorescence assay. An IgG titer > or = 32 and IgM titer > or = 16 were considered positive. The prevalence of positive IgG titer in the study population was 53 +/- 16% (mean +/- SD, age group range 14-66%). Neither seasonal nor gender-based difference in IgG antibody prevalence was demonstrated. It was lowest in the youngest group, 0-9 years old (p < 0.001), but rose linearly to age 70 (p < 0.005). 34 samples were IgM positive on initial testing; most from the older age groups. 12 were rheumatoid factor positive as well. After treatment with caprine antihuman IgG antibodies all became negative. The prevalence of C. pneumoniae infections is high in Iceland according to these results and similar to that in neighbouring countries. The presence of IgM rheumatoid factor may cause false positive tests for pathogen-specific IgM by immune complex binding with pathogen-specific IgG, thereby requiring its removal before testing.
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