Publication:

Role of autofluorescence technique in detection of mycobacterial bacilli on fine needle aspiration cytology in tubercular lymphadenitis in comparison to conventional methods

Background Lymphadenopathy is the most common presentation of extrapulmonary tuberculosis. Fine needle aspiration cytology (FNAC) has emerged an important role in the evaluation of peripheral adenopathy as a possible non-invasive procedure. Conventional Ziehl-Neelsen (ZN) method for acid fast bacilli (AFB) plays an important role in the diagnosis and the monitoring of treatment in tuberculosis. Fluorescence microscopy using auramine-rhodamine (AR) or Papanicolaou (PAP) staining has been considered superior to ZN staining.

Methods The study was conducted in tertiary care centre for a period of 2 years. A total number of 75 patients were included in the study. Four smears made from each aspirate: three air dried smears were stained with Giemsa, ZN, and AR stains and one was wet fixed for PAP stain for autofluorescence. Aspirate sent for culture over Lowenstein-Jensen medium was taken as a reference method.

Results Seventy five aspirates reported as tuberculous lymphadenitis on cytomorphology were stained with various methods. Autofluorescence was of more diagnostic utility for detection of AFB when cytologically only necrosis (64.71%) or granulomatous lymphadenitis (42.11%) was seen. With necrotising granulomatous lymphadenitis reported cases, Auramine Rhodamine was positive in maximum cases (66.7%) and was significant statistically. Overall taking culture as gold standard ZN stain was most specific (100%) and Auramine Rhodamine was most sensitive (82%).

Conclusions There is a definite advantage of autofluorescence in detecting mycobacteria over Ziehl-Neelsen and auramine rhodamine stain as it is more sensitive as well as an inexpensive technique. Autofluorescence can be a useful addition to routine cytology for early diagnosis and effective treatment.