Methods for diagnosing Mycobacterium tuberculosis infection in a human that include providing blood serum, contacting the serum with an Eis antigen fixed on a substrate, thereby forming complexes of Eis antigen with a human antibody that binds to the Eis antigen, contacting the antibody/Eis complexes with a labeled anti-human secondary antibody, and measuring a titer of the human antibody bound to the Eis antigen. In addition, statistically significant positive or negative diagnosis of infection with Mycobacterium tuberculosis is provided by comparing patient serum antibody titer with a second titer from a negative control blood sample.