Agreement between Direct Fluorescent Microscopy and Ziehl-Neelsen Concentration Techniques in Detection of Pulmonary Tuberculosis in Northwest Ethiopia

Abstract

BACKGROUND: The sensitivity of smear microscopy for diagnosisof tuberculosis might be improved through treatment of sputumwith sodium hypochlorite and application of fluorescentmicroscopy. This study aimed to determine the agreement betweendirect Fluorescent Microscopy and Ziehl-Neelsen concentrationtechnique by their ability of detecting acid fast bacilli in resourcepoor settings.METHODS: A cross sectional study was conducted at GondarUniversity Referral Hospital, Northwest Ethiopia. Three sputumspecimens were collected from consecutive TB suspects. Direct andconcentrated sputum smears were air-dried, heat-fixed and stainedby auramine O and Ziehl-Neelsen staining techniques respectively.The stained slides were examined for acid fast bacilli using directFluorescent Microscopy and Ziehl-Neelsen concentrationtechniques.RESULTS: Of 293 specimens, 4.4% and 2.4 % were AFB positiveby direct fluorescent microscopy and Ziehl-Neelsen bleachconcentrated techniques respectively. There was high percentage oftuberculosis positivity from early morning sputum samples (2.4%)compared to first spot (1.4%) and second spot (1.7%) sputumsamples when using Ziehl-Neelsen sodium hypochloriteconcentration technique. A moderate agreement was seen betweenthe two methods (Kappa=0.484, P value<0.001).CONCLUSION: Direct fluorescent microscopy has shown highpositivity rate compared to Ziehl-Neelsen concentration technique.A moderate agreement was seen between the two methods. Thus,Ziehl-Neelsen bleach sedimentation technique is recommended fordetection of pulmonary tuberculosis at peripheral health servicelevel when Fluorescent Microscopy is not available.