Novel hypertonic saline-sodium hydroxide (HS-SH) method for decontamination and concentration of sputum samples for Mycobacterium tuberculosis microscopy and culture

J Med Microbiol. 2008 Sep;57(Pt 9):1094-1098. doi: 10.1099/jmm.0.2008/001339-0.

Abstract

This study evaluated a new decontamination and concentration (DC) method for sputum microscopy and culture. Sputum samples from patients with suspected pulmonary tuberculosis (TB) (n=106) were tested using the proposed hypertonic saline-sodium hydroxide (HS-SH) DC method, the recommended N-acetyl-L-cysteine-sodium citrate-sodium hydroxide (NALC-NaOH) DC method and unconcentrated direct smear (Ziehl-Neelsen) techniques for the presence of mycobacteria using Löwenstein-Jensen culture and light microscopy. Of 94 valid specimens, 21 (22.3%) were positive in culture and were further characterized as Mycobacterium tuberculosis. The sensitivity for acid-fast bacilli (AFB) smears was increased from 28.6% using the direct method to 71.4% (HS-SH) and 66.7% (NALC-NaOH) using DC methods. Both concentration techniques were highly comparable for culture (kappa=0.794) and smear (kappa=0.631) for AFB. Thus the proposed HS-SH DC method improved the sensitivity of AFB microscopy compared with a routine unconcentrated direct smear; its performance was comparable to that of the NALC-NaOH DC method for AFB smears and culture, but it was methodologically simpler and less expensive, making it a promising candidate for evaluation by national TB control programmes in developing countries.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriological Techniques
  • Decontamination / methods*
  • Humans
  • Mycobacterium tuberculosis / isolation & purification*
  • Saline Solution, Hypertonic / chemistry*
  • Sensitivity and Specificity
  • Sodium Hydroxide / chemistry*
  • Specimen Handling / methods
  • Sputum / microbiology*
  • Tuberculosis, Pulmonary / diagnosis
  • Tuberculosis, Pulmonary / microbiology*

Substances

  • Saline Solution, Hypertonic
  • Sodium Hydroxide