Does Bleach Method Enhance Smear Positivity Of Tuberculosis Lymph Node Aspirates? A Systematic Review

Background and aims: Tubercular lymphadenitis (TBL) is most common form of extrapulmonary tuberculosis both in children and adults. Acid fast bacilli (AFB) positivity in fine needle aspiration cytology (FNAC) specimens is low; culture is time consuming and has limited availability; and newer molecular methods are costly and availability is limited. Improvement in microscopy, such as bleach method, would be a valuable tool to diagnose TBL. We aim to evaluate efficacy of bleach method to enhance smear positivity of Tuberculosis Lymph Node Aspirates. Methods: We included studies where bleach method was compared with routine AFB staining on FNAC specimens. We searched PubMed, EMABASE and Cochrane Database Reviews. Two authors independently selected studies and extracted data for review. Results: A total of three studies (305 patients) were included. The AFB positivity rate for routine ZN staining and bleach method was 27.0 % (27/100) vs 72.0% (72/1000), 33.3% (31/93) vs 63.4% (59/93), and 12.5 % (14/112) vs 60.7% (68/112) in three studies respectively. The studies reported that bleach method was easy, quick and less expensive. We could not combined data for pooled sensitivity and specificity as no reference standard was used in any of the included studies. Conclusions: The limited available literature suggests that AFB positivity of FNAC specimen from TBL is higher for bleach method as compared to routine ZN staining. The finding is of considerable interest for resource poor countries where microscopy is only tool to diagnose TBL. Further studies are needed with proper reference standard before recommending bleach method routinely.