Health Questions and Answers

Question: How should results of sputum microscopy be interpreted?


  • SMEAR POSITIVE if at least two sputum specimens are AFB (+)
  • SMEAR NEGATIVE if none of the specimens are AFB (-)
  • DOUBTFUL When only one of the 3 sputum specimens is (+).
    • When results are doubtful, a second set of three must be collected again
    • If at least one of the second three is (+), the diagnosis is SMEAR POSITIVE.
    • If all of the second three are (-), the diagnosis is SMEAR NEGATIVE

Reference: Diagnosis, Treatment, Prevention and Control of Tuberculosis in Adult Filipinos: 2006 UPDATE 2(3): 46-47

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