Chronic Chlamydophila pneumoniae infection in lung cancer, a risk factor: a case-control study.

The relationship between chronic Chlamydophila (formerly Chlamydia) pneumoniae infection and lung carcinoma was investigated. A total of 123 patients who were smokers and diagnosed with lung carcinoma based on clinical and laboratory (radiological, cytological) findings were examined. Of these patients, 70 had small-cell, 28 squamous-cell and seven large-cell carcinomas, while 18 had adenocarcinoma. A total of 123 healthy persons matching patients in age, sex, duration of smoking and locality were chosen as controls. Blood samples (5 ml) were withdrawn at the time of diagnosis and 1 month later. The values between IgG >/= 512 and IgA >/= 40 were set as the criteria for chronic Chlamydophila pneumoniae infections. In male patients with lung carcinoma, Chlamydophila pneumoniae IgG antibody titres of >/= 512 and IgA antibody titres of >/= 40 were found at a higher rate than in the control group. This ratio was not significant for the female patients. In chronic Chlamydophila pneumoniae infections, Chlamydophila pneumoniae antibody titres with values IgG >/= 512 and IgA >/= 40 were found in a total of 62 (50.4 %) cases. Chronic Chlamydophila pneumoniae infections were seen statistically more often in male patients with carcinoma who were aged 55 years or younger. This study supports the idea that chronic Chlamydophila pneumoniae infection increases the risk of lung carcinoma.