Plasmacell-free DNA assay: a diagnostic tool for tuberculosis lymphadenitis.

BACKGROUND: Bacterial confirmation in suspected tuberculosis lymphadenitis patients is challenging. This study evaluates plasmacell-free DNA as a diagnostic tool for tuberculosis lymphadenitis.

METHODS: A quantitative PCR assay targeting IS, IS, andgenes was performed on plasma samples. The study included 95 tuberculosis lymphadenitis patients and 60 controls. Sensitivity of the plasmacell-free DNA assay was assessed against fine needle aspiration GeneXpert Ultra, fine needle aspiration culture, and fine needle aspiration cytology, while specificity was determined using control groups.

RESULTS: Of the tuberculosis lymphadenitis cases, 71 (74.7%) were bacteriologically confirmed, and 24 (25.3%) were probable. In the control group, 50% had latent tuberculosis infection. Thecell-free DNA assay, targeting three genes, had an overall sensitivity of 65.3%, increasing to 70.4% for confirmed cases and 50% for probable cases, with specificity of 91.1%. Sensitivities for specific gene combinations were 62.1% for ISand IS, 54.7% for ISand, and 55.8% for ISand. For individual genes, ISshowed 49.4% sensitivity (specificity: 93.3%), IShad 51.6% (specificity: 96.0%), andshowed 28.4% (specificity: 96.7%). Combining positive results from all three genes in the cell-free DNA assay with fine needle aspiration culture and GeneXpert Ultra improved sensitivity to 76.8% and 85.3%, respectively.

CONCLUSION: This study demonstrated thatcell-free DNA can be detected in the plasma of over half of tuberculosis lymphadenitis patients. The plasmacell-free DNA assay could serve as a valuable, less-invasive complement to existing fine needle aspiration diagnostics.