A meta-analysis of the association between Chlamydia pneumoniae infection and lung cancer risk

The association between Chlamydia pneumoniae infection and lung cancer risk was not clear with small number of cases in each study. The aim of this meta-analysis was to evaluate the correlation between pneumonia infection and lung cancer risk by pooling the open published papers.

We searched the electronic databases of Medline, EMBASE, Web of Science, and China National Knowledge Infrastructure databases for publications related to the association between pneumonia infection and lung cancer risk. Odds ratio (OR) and its 95% confidence interval (95% CI) was used to assess the correlation. The data were pooled by Stata 11.0 software (Stata Corporation, College Station, TX, USA).

Thirteen publications, involving 2549 lung cancer patients and 2764 controls were included in this meta-analysis. The pooled results indicated that the C. pneumoniae infection significant increased the risk of lung cancer OR = 2.07 (95% CI: 1.43-2.99) by random effect model. And for serum IgG, 12 publications reported the IgG positive rate in lung cancer patients and relative healthy controls. The pooled OR was 2.22 (95% CI: 1.41-3.50) by using the random effects model which indicated that the IgG positive rate was significantly higher in lung cancer patients than that of healthy controls. The sensitivity analysis indicated the pooled OR was not sensitive to a single study. However, Begger's funnel plot and Egger's line regression analysis indicated significant publications bias for this meta-analysis.

According to the present published data, C. pneumoniae infection may increase the risk of lung cancer. However, for its significant publications and heterogeneity among the included studies, the conclusion should be interpreted cautiously.