Evaluation of urinary extracellular vesicles and microRNAs to diagnose urogenital tuberculosis

India has the highest tuberculosis (TB) burden in the world. Of the estimated annual 10 million TB cases, features of extra pulmonary TB are evident in up to 45%. Urogenital TB (UGTB) accounts for approximately 20% of those cases. The lack of non-sputum based diagnostic tools continue to hinder efforts to reduce the burden of UGTB. MicroRNAs (miRNAs) play a crucial role in biological pathways and can be used as a potential biomarker for TB. We evaluated urinary extracellular vesicles (uEVs) as non-invasive source to explore miRNAs with biomarker potential for UGTB.

To evaluate the potential of miRNA-155-5p, miRNA-26a-5p and miRNA-29a-3p in uEVs to diagnose UGTB in adults.

uEV characterization was done using nanoparticle tracking analysis and flow cytometry. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) for urinary uEV-miRNAs were carried out in samples from patients with suspected UGTB, or Urinary tract infections [UTI, disease controls (DC)] and healthy controls (HCs) (n = 20/group). U6 was used to normalize the qRT-PCR data. Receivers operating characteristic curves was used to calculate the diagnostic accuracy of uEV-miRNAs to differentiate UGTB from controls (DC and HCs).

uEVs from UGTB or UTI patients had higher mean size, and also lower proportion of CD63 positive vesicles as compared to HC's uEVs. Between UTI and UGTB, the mean size of uEVs was significantly higher in UTI cases. qRT-PCR analysis revealed a significantly lower abundance of miRNA-155-5p and miRNA-26a-5p in uEVs from UGTB relative to UTI (P value = 0.004) and HC (P value = 0.009) respectively n = 20/group). While, miRNA-29a-3p was higher in abundance in both UGTB and HCs' uEV, relative to uEVs from UTI cases (P values = 0.004 and 0.002 respectively, n = 20/group). Moreover, miRNA-155-5p [area under curve (AUC) = 0.88, P ≤ 0.0001] and miRNA-29a-3p (AUC = 0.76, P value = 0.005) had optimal diagnostic accuracy to differentiate UGTB from DC (n = 20/groups) with a likelihood ratio of 5.2 and 4.3, respectively through receivers operating characteristic curve. While, miRNA-155-5p (AUC = 0.68, P value = 0.05) and miRNA-26a-5p (AUC = 0.78, P value = 0.002) had optimal diagnostic accuracy to differentiate UGTB from HCs with a likelihood ratio of > 2.

The differential expression of uEV-miRNAs, miRNA-155-5p and miRNA-29a-3p in UTGB and UTI cases hold promise in the specific diagnosis of UGTB. Further studies in large cohort are, however, needed to confirm the diagnostic accuracy of these uEV-miRNAs.