Comparison of Ziehl Neelsen and Auramine O staining methods on direct and concentrated smears in clinical specimens.
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Date
2011-04
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Abstract
Background: In developing countries like ours with a large number of tuberculosis (TB) cases and limited resources, the
diagnosis of TB relies primarily on smear microscopy for Acid Fast Bacilli (AFB) but its sensitivity is limited in paucibacillary
cases.
Aim: To evaluate the increase in efficacy of smear microscopy when smears are prepared from clinical samples after
concentration by Petroff’s method and stained by Auramine O (AO) fluorescent dye as against Ziehl Neelsen (ZN) staining
of similar taking culture as the gold standard.
Methods: Smears were prepared from 393 clinical samples both by direct and after Petroff’s concentration and examined
by fluorescent microscopy and Ziehl Neelsen method .The concentrated material was also cultured on Lowenstein Jensen
media and the results of the two microscopy methods were compared with the culture results taken as the gold standard.
Results: Mycobacterial growth was detected in 137(35.77%) specimens, out of which three were non-tubercular
mycobacteria. Using culture as the reference method, the sensitivity of direct staining was 55.55% for ZN and 71.85% for
AO. Direct fluorescent microscopy detected 9.29% paucibacillary sputum samples that were missed on ZN staining. On
concentration, the sensitivity increased by 6.67% for ZN and 11.11% for AO. The sensitivity of AFB smear microscopy
increased by 27.41% and was statistically significant (p=<.001) when both methods were combined. The specificity was
99.19% for both ZN and AO.
Conclusion: Fluorescent microscopy has higher sensitivity and comparable specificity which is further enhanced by
concentration. Now with the advent of newer inexpensive Light Emitting Diode (LED) based fluorescent microscopes
(FM), which are easier to use, fluorescent microscopy can be widely used even in peripheral laboratories where culture
facilities are not available.
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Keywords
Ziehl-Neelsen Staining, Mycobacterium tuberculosis, Auramine O
Citation
Hooja Saroj, Pal Nita, Malhotra Bharti, Goyal Sumit, Kumar Vipin, Vyas Leela. Comparison of Ziehl Neelsen and Auramine O staining methods on direct and concentrated smears in clinical specimens. Indian Journal of Tuberculosis. 2011 Apr; 58(2): 72-76.