. Diagnostic Microbiology
The presence of acid-fast-bacilli (AFB)
on a sputum smear or other specimen
often indicates TB disease. Acid-fast
microscopy is easy and quick, but it
does not confirm a diagnosis of TB
because some acid-fast-bacilli are not
M. tuberculosis. Therefore, a culture is
done on all initial samples to confirm the
diagnosis. (However, a positive culture
is not always necessary to begin or
continue treatment for TB.) A positive
culture for M. tuberculosis confirms
the diagnosis of TB disease. Culture
examinations should be completed on
all specimens, regardless of AFB smear
results. Laboratories should report
positive results on smears and cultures
within 24 hours by telephone or fax to
the primary health care provider and to
the state or local TB control program, as
required by law