Improved Diagnosis of Pulmonary Tuberculosis using Bleach (Sodium hypochlorite) Concentration Technique at Tertiary Care Hospital

Abstract

Introduction: In the Revised National Tuberculosis Control Program (RNTCP), microscopic examination of sputum for acid-fast bacilli (AFB) is currently the backbone for the diagnosis of pulmonary tuberculosis. Studies have shown liquefaction and concentration of sputum by 5% sodium hypochlorite is useful in providing increased sensitivity and safety for the handling of specimens. Objective: To assess the utility of the 5% Sodium hypochlorite concentration method in increasing the sensitivity of smear microscopy for detection of AFB for diagnosis of pulmonary tuberculosis. Methods: The study included a total of 1000 sputum samples from 500 patients with suspected pulmonary tuberculosis. Direct smears were prepared from the sputum samples as per RNTCP guidelines. The remaining sputum was used for bleach concentration and smears prepared from the concentrated material. Both smears were stained by Ziehl-Neelsen staining and screened for acid-fast bacilli and graded according to the RNTCP guidelines. Results: A total of 158 samples (15.8%) from 89 patients were positive by a routine direct method whereas by concentration method 236 samples (23.6%) from 143 patients were found positive diagnosing additional 54 patients. The gain in sputum smear positivity of 7.8% over the routine method is highly significant (p=0.0000, χ2= 270) with a 10.8% increase in case detection. Conclusions: Improvement in the sensitivity of smears microscopy will be useful in case detection of tuberculosis especially in resource-poor countries. The increased positivity of microscopy by bleach method indicates that would prove useful if included in the RNTCP to improve case detection. Keywords: Concentration; smear positivity; sodium hypochlorite; tuberculosis.

Role of Bleach Concentration Method for Detection of Acid-fast Bacilli (AFB) in Sputum using Conventional Ziehl-Neelsen (ZN) Staining Technique

“…2 In developing countries such as India, sputum microscopy with Ziehl-Neelsen (ZN) staining is used to identify tuberculosis because it is simple, inexpensive and provides rapid results. 3,4 Bleach (sodium hypochlorite, NaOCl) can be used as an ideal chemical processing agent in a resource-poor country. To enhance the yield of AFB for diagnosing pulmonary tuberculosis, digestion of sputum sample with bleach is suggested by some researchers.…”