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Indian J Tuberc. 2012 Oct;59(4):219-23.

Equivalence of acid alone or acid-alcohol as decolourizing agent in Ziehl-Neelsen method.

Author information

  • 1Department of Bacteriology (Retd), National Institute for Research in Tuberculosis (ICMR), Chetput, Chennai - 600 031, Tamil Nadu.

Abstract

BACKGROUND:

Microscopists opine that acid-alcohol decolourized slides may enhance acid-fast bacilli (AFB) smear positivity, and published documents on equivalence of acid and acid-alcohol in ZN staining method are not easily accessible.

SETTING:

National Institute for Research in Tuberculosis, Chennai, India.

OBJECTIVE:

To document the equivalence of 25% sulphuric acid (ZN-acid method) and 3% hydrochloric acid-alcohol (ZN-alcohol method) as decolourizing agents in ZN method for detection of acid-fast bacilli.

METHODS:

Two smears from each of 253 sputum samples from pulmonary tuberculosis patients, prepared and allocated, one to ZN-acid method and another to ZN-alcohol method were read blind. All the specimens were cultured for Mycobacterium tuberculosis by modified Petroff's method. Culture of M. tuberculosis was gold standard.

RESULTS:

The concordance between the methods was 85% (kappa 0.68), and the sensitivity (79%) and specificity (89%) were same for both the methods.

CONCLUSION:

In conclusion, the common belief that acid-alcohol decolourized slides give enhanced smear positivity stands void.

PMID:
23342542
[PubMed - indexed for MEDLINE]
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