SMEAR
MICROSCOPY - SCI & TECH
News:
In TB detection, smear
microscopy’s share still holds sway
What's
in the news?
● Last
year in India the traditional sputum smear microscopy was the initial
diagnostic investigation for 77 percent of the suspected patients though WHO
recommended the use of molecular diagnostics.
Smear
Microscopy:
● In
Sputum smear microscopy, a patient’s sputum
(a mixture of saliva and mucus coughed up from the respiratory tract) is
collected and examined under a microscope after staining with a special dye.
● The
presence of acid-fast bacilli (AFB),
which include Mycobacterium tuberculosis,
can be observed under the microscope.
● While
sputum smear microscopy is simple and cost-effective, it has limitations.
Limitation:
● May
not detect all cases of TB.
● Only
about 50% sensitivity.
● It
cannot determine drug resistance.
The WHO guidelines clearly stated that GeneXpert may
be used rather than conventional microscopy and culture as the initial
diagnostic test in all adults suspected of having TB.