Evaluation of modified bleach technique for the detection of acid fast bacilli in lymph node aspirate at the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia

Background: Tuberculous Lymphadenitis (TBLN) is the commonest form of extrapulmonary tuberculosis. Definitive diagnosis of TBLN is difficult due to the low efficacy of the routine diagnostic techniques as compared to culture. Objective: To determine whether prior bleach concentration can improve the detection of acid-fast bacilli when compared with conventional Ziehl-Neelsen (ZN) staining by using culture as the gold standard. Methods: Cross-sectional study was conducted from March 01, 2015 to May 30, 2015. The study subjects were clinically suspected TBLN patients. Fine needle aspiration (FNA) was performed. Two different smears were prepared directly from the first needle pass for cytology and ZN staining. The remaining aspirate was used for the modified bleach concentration. The second needle pass aspirate was transferred into a sterile container containing sterile normal saline. The sediment was inoculated on the Lowenstein Jensen (LJ) medium. Measurement parameters for reliability and validity were used to analyze the results. Result: A total of 93 participants were included in the study. Fifty-six out of the 93 (60.2 %) cases were positive for mycobacterium tuberculosis complex on LJ culture. The detection rates of direct ZN staining and modified bleach method were 20.4 % and 44.1 %, respectively. 73.1 % of the cases showed cytomorphological features consistent with TBLN by cytologic examination. The sensitivities of direct ZN staining and modified bleach method and cytomorphology were 32.0 %, 67.8 %, and 92.8 %, respectively. Conclusion: Implementation of bleach concentration increases the detection rate of AFB over the direct ZN method. The bleach method can also be easily performed and provide a safe working environment by reducing infections.

Abstract licence: CC BY-NC

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