Evaluation of Pot’s Technique and Sodium Hypochlorite Concentration Technique in Smear Negative Sputum Samples for Increased Sensitivity of Sputum Microscopy

Abstract

Introduction: In developing countries, diagnosis of pulmonary tuberculosis is primarily based on microscopy owing to its simplicity, less cost and rapidity. Various ways to improve the sensitivity with multiple samples and concentration of sputum have been used. Simple methods which can be used in microscopic centers are desirable. Aim: This study was planned to evaluate the sensitivity of sputum smear examination by Pot’s technique and Sodium hypochlorite concentration technique over conventional Revised National Tuberculosis Program (RNTCP) method. Materials and Methods: A cross-sectional analytical study was carried out in all non-repetitive sputum smear negative samples obtained in Mycobacteriology laboratory after obtaining the Institutional Ethics Committee clearance with waiver of consent during a time period from 1st July to 31st August 2018. Two sputum samples (one morning and one spot) received from 47 outdoor and indoor patients in Mycobacteriology department of tertiary care hospital were included in study. All samples were first processed by routine Ziehl-Neelsen (ZN) staining. Sputum smear negative were subjected to Pot’s technique and Sodium hypochlorite concentration technique to evaluate the efficacy of these concentration techniques. All data was maintained in MS Excel and analysed using test of proportion and test of significance. Results: A total of 94 samples received from 47 patients were analysed. 04/94 (4.25%) samples were positive for AFB by routine RNTCP staining. With use of Sodium hypochlorite concentration method and Pots method, 05/94 (5.31%) and 06/94 (6.38%) samples were positive indicating a rise of 1.06% and 2.1% respectively over conventional. Additional two cases were detected compared to RNTCP, amounting to 100% rise in case detection which otherwise would have been missed. Conclusion: Concentration methods are easy to perform, safe for handlers without requirement of additional human resource. Good smear quality with less debris in microscopic field aids in improving detection rate over conventional methods.

Keywords

• mycobacteriology
• phenol and ammonium sulphate
• pulmonary tuberculosis
• ziehl-neelsen staining