Since Koch’s discovery of the bacillar etiology of
tuberculosis (TB), diagnosis of the disease by the conventional
smear/culture method has remained essentially unchanged. Smears
detected the acid-fast bacillus (AFB), and cultures determined whether
the AFB detected was a mycobacterium TB (MTB). Innovation amounted to a
few new smear stains and an array of diversified culture media.
The method left much to be desired. Smears missed about 50% of
culture-proven cases, and could not differentiate MTB from other
mycobacteria (MOTT). The more sensitive and specific cultures detected
up to 80% of active cases, but took 2 to 8 weeks for completion.
Without an immediate diagnosis, the clinician had to prescribe in full
the four-drug regimen to all suspected TB patients for up to 2 months.
Considering that only one of five or six of these patients finally
qualified for class III (having active disease), there was a fivefold
to sixfold waste of public health resources during the first 2 months
of all treatments. For the unnecessarily treated, personal damage could
be heavy in terms of drug side effects, loss of work, and the potential
humiliation from different public health interventions (directly
observed therapy, isolation, contact investigation, etc) that any
unskillful handling by public health staff could turn into harassment
and violation of patients’ rights.