FIG. 2.

The PPE protein Rv1168c is more sensitive for discriminating TB patients from the BCG-vaccinated controls. The scatter plot shows the serum cross-reactivities by EIA to the mycobacterial recombinant Rv1168c, mycobacterial recombinant ESAT-6, Hsp60, and PPD with serum from either active tuberculosis patients or BCG-vaccinated controls. The horizontal line indicates the mean of the absorbance values (A). The EIA antibody responses of individual patients whose results are shown in panel A were compared between Rv1168c and Hsp60 (B, panels i to iii). Responders to Rv1168c were compared with that of ESAT-6, Hsp60, and PPD by calculating the percentage of TB patients showing absorbance value greater than or equal to the cutoff value, calculated as the mean OD₄₉₂ of control sera plus 6 SD (C). Mean OD₄₉₂ (SD) values used for cutoff determinations were as follows: Rv1168c, 0.376 (0.066); ESAT-6, 0.343 (0.07), Hsp60, 0.359 (0.08); PPD, 0.295 (0.071). Statistical significance was determined with Student's t test.