Molecular evidence for the role of mycobacteria in sarcoidosis: a meta-analysis

The aetiology of sarcoidosis is currently unknown. Due to the clinical and histological similarities between sarcoidosis and tuberculosis, the role of mycobacteria has been repeatedly investigated as an aetiological agent for sarcoidosis. The current meta-analysis aimed to evaluate the available molecular evidence on the possible role of mycobacteria in the development of sarcoidosis. The MEDLINE, EMBASE, CINAHL, DARE and CENTRAL databases were searched for relevant studies published from 1980 to 2006, and studies evaluating the presence of mycobacteria using molecular techniques in biological samples of patients with sarcoidosis were included in the current analysis. The 95% confidence intervals (CI) were calculated for the expected proportion (of individual studies); the data was then pooled to obtain a summary success rate with 95% CI. The odds ratio (95% CI) was also calculated in order to assess the presence of mycobacteria in samples of patients with sarcoidosis versus those from nonsarcoidosis control samples. The database search yielded 31 studies. All studies used polymerase chain reaction for nucleic acid amplification followed by identification of nucleic acid sequences specific for different types of mycobacteria. Overall, 231 out of the 874 patients were positive for mycobacteria with a positive signal rate of 26.4 (23.6-29.5%), and the odds of finding mycobacteria in samples of patients with sarcoidosis versus controls were 9.67 (4.56-20.5%) using the random effects model and 19.49 (11.21-35.54%) using the exact method. There was methodological and statistical heterogeneity and evidence of publication bias. The results of the current study illustrate a demonstrable mycobacterial presence in sarcoidosis lesions suggesting an association between mycobacteria and some cases of sarcoidosis. To avoid methodological diversity, larger multicentre trials with a central laboratory for sample testing should be designed.