The miRNA is a class of small molecule non-coding RNA with a length of about 20-24 bp ,which is transcrip-tion from the endogenous gene .The hairpin structure and the post-transcriptional regulation of gene expression are its typical characteristics .It is suggested that the miRNA play an important control and management role in latent infection and active in-fection in tuberculosis ,and the expression situation of miRNA is also different between latent infection and active infection in tuberculosis .Some studies also found that there are differences in the expression of miRNAs such as miR-155 ,miR-29a ,miR-361-5p ,miR-889 ,miR-576-3p and so on ,as a marker of TB diagnose .

Objective To evaluate the possibilities of using circulating miR-155-5p, miR-21-5p, miR-29a and miR-142-5p as biomarkers for the diagnosis of active pulmonary tuberculosis (TB).Methods Plasma samples were collected from 60 healthy subjects, 40 patients with active pulmonary TB and 20 sub-jects with latent tuberculosis infection ( LTBI) to extract miRNAs.The levels of miR-155-5p, miR-21-5p, miR-29a and miR-142-5p in plasma samples were detected by using reverse transcription-quantitative PCR. Results The levels of miR-155-5p, miR-21-5p and miR-29a in patients with active pulmonary TB were re-spectively 10.13, 7.34 and 2.74 times as much as those in healthy subjects(P<0.05).No significant differences with the level of miR-142-5p were observed between the two groups.The receiver operating char-acteristic (ROC) curve analysis of miR-155-5p, miR-21-5p and miR-29a in patients with active pulmonary TB and healthy subjects showed that the areas under the curve (AUC) were respectively 0.905, 0.830 and 0.687.The level of miR-155-5p in patients with LTBI was 3.1 times than that in healthy subjects ( P<0. 05).No differences with miR-21-5p, miR-29a and miR-142-5p were found between patients with LTBI and healthy subjects.The levels of miR-155-5p, miR-21-5p and miR-29a in patients with active pulmonary TB were respectively 3.26, 6.69 and 1.98 times than those in patients with LTBI (P<0.05).The rate of LTBI was 40.58%in people who were in close contact with patients with active pulmonary TB.Conclusion Sig-nificant differences with the levels of miR-155-5p, miR-21-5p and miR-29a were observed among healthy subjects, patients with active pulmonary TB and patients with LTBI, but no difference with the level of miR-142-5p was observed among them.miR-155-5p, miR-21-5p and miR-29a could be used as the potential bio-markers for the diagnosis of active pulmonary tuberculosis and latent tuberculosis infection.People who were in close contact with patients with active pulmonary TB could have a higher LTBI rate.