[Role of enzyme-linked immunospot assay and tuberculin skin test in the auxiliary diagnosis of initial pulmonary tuberculosis].

Objective: To compare enzyme-linked immunospot assay (ELISPOT) and tuberculin skin test (TST) and explore their roles in the auxiliary diagnosis of initial pulmonary tuberculosis.

Methods: Totally 123 patients with initial pulmonary tuberculosis (tuberculosis group) and 102 patients with non-tuberculosis pulmonary disease (control group) were enrolled. The peripheral blood mononuclear cells of all participants were co-cultured with early secretiny antigen target-6/culture filtrate protein-10 fusion protein (ESAT-6/CFP-10), and spot forming cells (SFCs) were enumerated by ELISPOT (ESAT-6/CFP-10-ELISPOT). TST was also performed simultaneously.

Results: ESAT-6/CFP-10-ELISPOT showed significantly higher numbers of SFCs after stimulation in tuberculosis group than in control group (P = 0.000). The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, and negative predictive value of ESAT-6/CFP-10-ELISPOT were 91.1% (111/123), 81.4% (82/102), 4.60, 0.12, 0.85, and 0.87 respectively, while the above values of TST were 65.6% (59/90), 45.1% (46/102), 1.31, 0.76, 0.51, and 0.60, respectively. The sensitivity and specificity of ESAT-6/CFP-10-ELISPOT were significantly higher than those of TST (all P = 0.000). The number of SFCs were not significantly different between smear-positive tuberculosis subgroup and smear-negative tuberculosis subgroup (P = 0.166). The sensitivities were 91.8% (67/73) and 88.0% (44/50) in these two subgroups, respectively, (P = 0.448).

Conclusions: ESAT-6/CFP-10-ELISPOT may be a more accurate approach for the auxiliary diagnosis of initial pulmonary tuberculosis; meanwhile, it offers certain diagnostic evidences for smear-negative tuberculosis. However, its specificity may be affected by latent tuberculosis infection. On the contrary, TST has poor value in the auxiliary diagnosis of initial pulmonary tuberculosis.