KUMJ | VOL. 7 | NO. 3 | ISSUE 27 | JULY-SEPT, 2009

A comparative study of fl uorescent microscopy with Ziehl-Neelsen staining and culture for the diagnosis of pulmonary tuberculosis
Laifangbam S, Singh HL, Singh NB, Devi KM, Singh NT

Background: For developing countries with a large number of cases and financial constraints, evaluation of rapid and inexpensive diagnostic methods has great importance. The bacilli in the sputum can be detected microscopically by ZN stain and fl uorochrome stain.
Objectives : To study the effi cacy of fl uorescence microscopy in the diagnosis of pulmonary tuberculosis in comparison to Ziehl-Neelsen staining and culture of sputum samples from patients suspected of pulmonary tuberculosis.
Materials and methods : 306 sputum samples collected from 102 patients suspected of pulmonary tuberculosis were processed by the Petroff’s method, and subjected to Ziehl-Neelsen staining (ZN), fl uorescent Auramine-O staining (AO) and culture on modifi ed Lowenstein-Jensen media (gold standard) for detection of Mycobacterium tuberculosis. Positive smears were graded according to Forbes BA et al, and culture isolates were biochemically tested for confi rmation of species.
Results : Out of 102 patients, 44.1%, 71.6% and 70% were found positive by ZN, AO and culture respectively. AO was found to be superior to ZN on several aspects. The difference in their case detection rates was statistically significant (χ2 = 24.93, p < 0.001). AO was also able to detect more pauci-bacillary cases than ZN. There was more agreement between culture and fl uorescence microscopy (95.1%) than with ZN microscopy (69.6%). The percentage of false negative by AO staining was only 2.78% which was in sharp contrast to that of ZN (40.27%).
Conclusion: The better case detection rates of AO over ZN were comparable to those found by several studies. Since screening was done under lower power of magnifi cation (400x), fl uorescence microscopy has been found to be less time consuming as compared to ZN method (1000x) in the diagnosis of tuberculosis. The tubercle bacilli stood out as bright objects against a dark background in fl uorescence microscopy which makes them easily identifi able hence causing less eye-strain. The effi cacy of fl uorescence microscopy proved to be much higher than conventional light microscopy and
comparable to that of culture.