Tuberculosis Drug Treatments -- Acid-fast Smear
One of the most prevalent diagnostic technologies detects presence of the TB bacteria in sputum using an acid-fast smear (AFS) through microscopic examination, but is problematic because the technique is cumbersome, both for patients who need to return to the health care center at least twice to provide sputum samples, and for the technician straining to count Mycobacterium tuberculosis (MTB) bacilli using a sun-lit microscope.
The test has a sensitivity of only 40-60 percent under field conditions, falling as low as 20 percent in the presence of HIV co-infection. AFS testing is ineffective in detecting TB bacteria in individuals with low load levels, leading to “smear negative” results in people who have TB but are in the early stages of their infection.
Early-stage TB infection is less likely to cause death or be contagious to others; however, a delay in diagnosis of infection in these individuals, particularly those who may be drug resistant, can lead to increased illness, infection in others, or death.