Table 2 Summary of studies do not support the association between Chlamydia pneumonia infection and lung cancer
From: Chlamydia pneumoniae infections and development of lung cancer: systematic review
First author | Study setting | Methods | Results | Conclusion |
|---|---|---|---|---|
Serology-based investigations | ||||
Smith JS [19] | Case–control study. 163 histologically confirmed cases of lung cancer and 190 controls (of whom 90 and 68 were never smokers, respectively) | C. pneumoniae IgG and IgA antibodies were measured, blinded of case–control status, using a standardized microim-immunofluorescence (MIF) assay optimized for the detection of C. pneumoniae | The prevalence of IgG positivity was 78% among cases and 74% among controls (OR 5 0.90, 95% CI: 0.52–1.57) Corresponding OR estimates were 0.65 (95% CI: 0.20–2.13) among smokers and 0.86 (95% CI: 0.43–1.73) among non-smokers | This study offers no support to the hypothesis that C. pneumoniae infection is a significant cause of lung cancer in Europe, particularly among non-smokers |
Koh WP 1996–1998 [20] | Case–control study among Chinese women. Two hundred cases and 181 controls were included | Titers of IgG and IgA antibodies against C. pneumoniae were measured by indirect microimmunofluorescence (MIF) test kits | There was no association between chronic C. pneumoniae infection and lung cancer [Odds ratio (OR) 1.05, 95%confidence interval (CI) 0.61–1.80]. The null association remained when limited to non-smokers (OR 1.01, 95% CI 0.55–1.83). However, a possible association among younger subjects aged 60 years and below could not be excluded (OR 1.70, 95% CI 0.79 –3.67) | This study findings of a null association generally do not support the hypothesis that C. pneumoniae is independently associated with lung cancer among Chinese women, particularly in non-smokers |
Molecular-based investigation | ||||
Sessa [18] | An experimental study using lung biopsy specimens during surgery | Investigated the presence of C. pneumoniae DNA in tumor lung tissues by using real-time PCR assay. Simultaneously, tumor and healthy tissues from the same patient with primary carcinoma lung were analyzed | C. pneumoniae DNA was not detected in a single lung tumor tissue using a highly sensitive and specific real-time PCR assay based on FRET hybridization probes | This study does not support C. pneumoniae in the pathogenesis of lung cancer, suggesting that further investigations are needed to clarify other potential causative factors for the development of this malignancy |