A new test promises to tell Americans within hours, instead of days, if they have tuberculosis. The Food and Drug Administration approved Gen-Probe Inc.`s new spit test for tuberculosis, called the Mycobaterium Tuberculosis Direct Test. Now, doctors diagnose TB through an intensive laboratory test that takes a week, and sometimes more, to get test results. The FDA said the Gen-Probe test is 95 percent accurate and gives results in 4-5 hours. That means treatment can begin almost immediately.