MS JOSEPHINE NYABETA RIOKI

Citation:

JN R, J N, EA R, W J. "Comparative evaluation of direct Ziehl-Neelsen (ZN) smear and modified ZN against fluorescent technique in the detection of acid-alcohol fast bacilli in lymph node aspirates." East African Journal of Pathology. 2014;1:19-22.

Abstract:

Background: Tuberculosis is a major public health problem in Kenya as well as other developing countries. Diagnosis of extra-pulmonary tuberculosis is a common challenge especially where direct Ziehl Neelsen (ZN) technique is employed.
Objective: This study was aimed to establish whether modification of ZN by use of 3.5% NaOCl-Xylene Floatation would improve the detection of acid-alcohol fast bacilli (AAFBs) from lymph node aspirates.
Design: This was a descriptive cross-sectional study.
Setting: Kenyatta National Hospital, Kenya.
Subjects: One hundred cases suspected of clinically having TB with lymphadenopathy referred for fine needle aspiration cytology (FNAC) in FNA Clinic at Kenyatta National Hospital.
Methodology: The study was approved by Kenyatta National Hospital/ University of Nairobi/ Ethics and Research Committee (KNH/UON/ERC) and informed consent sought from patients. Analysis was done using SPSS version 12.0 for Windows (SPSS Inc.). McNemar’s test was used to assess the level of significance for the two test procedures. Chi-square was used to assess for the heterogeneity of the association between the two study methods.
Results: Thirty (30%) of the specimens were positive with fluorescent microscopy, 17% were modified ZN positive while 6% were direct ZN positive. The sensitivity, specificity, positive and negative predictive values for the modified technique (3.5% NaOCl-Xylene Floatation) were 53.3%, 98.6%, 94.1%, and 83.1% respectively.
Conclusions: Liquefaction of the aspirated specimens with NaOCl followed by Xylene floatation significantly increased the yield of AAFBs. This finding is of great interest in developing countries where smear-negative for acid-alcohol fast bacilli (AAFBs) has become common.
Recommendation: Local settings should consider adopting use of modified ZN technique in order to increase the sensitivity and detection rate of AAFBs from lymph node aspirates.