A Study for Detection of Missed Tuberculosis Cases at a Tertiary Care Centre in Northern Bihar, India

Abstract

BACKGROUND In resource limited settings, the diagnosis of pulmonary tuberculosis heavily rests upon the sputum smear examination by ZN staining or Auramine-O staining. Despite all expertise, lots of cases are being missed at the DOTS and Designated Microscopy Centres (DMCs) under RNTCP. So, there is need to adopt measures to increase the detection rate of sputum smear microscopy. The sputum samples declared negative for Acid fast bacilli by fluorescent staining method were decontaminated and concentrated by modified Petroff's method before performing ZN staining and were cultured to detect the missed positive cases. MATERIALS AND METHODS About 200 sputum samples which were declared negative after Auramine-O staining at DOTS centre were selected and processed by modified Petroff's method before performing ZN staining. Furthermore, they were cultured by manual BBL MGIT technique and the positive tubes were confirmed for presence of Mycobacteria by ZN staining. RESULTS Out of 200 sputum samples, 9 samples (4.5%) turned out to be positive by ZN staining after decontamination and concentration. Following MGIT culture 14 samples (7%) got contaminated, while in 186 samples which could be followed for 6 weeks 49 samples (26.34%) were found to be positive. The time for detection of Mycobacteria by MGIT ranged from about 5 to 13 days. CONCLUSION The study concludes that if decontamination and concentration technique like modified Petroff's method is adopted at DOTS and DMCs under RNTCP, the rate of detection of Mycobacteria will increase. Also, liquid culture methods like MGIT can be used for further enhancing the detection rate.