How To Interpret The Smear?
At least 100 oIl Immersion fields must be viewed before declaring the smear as negative The sensitivity of smear Is low because It requires the presence of 104 bacillilml to be smear positive. If the number of bacilli is less than this, the chances of detecting them are less In such a case, the sample should be subjected to concentration techniques such as Petroff s method If the smear Es positive for AFB. it should be counted/graded Failure to detect any AFB does not rule tuberculosis Grading of smears has prognostic value.
