Comparison of Ziehl Neelsen and Auramine O staining methods on direct and concentrated smears in clinical specimens.

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.

Enumeration of CD4 and CD8 T lymphocytes in healthy HIV seronegative adults of northwest India: a preliminary study.

CD4 T lymphocyte count is used to measure the progression of HIV infection and to monitor the response to antiretroviral therapy. Information on reference CD4 and CD8 T cell counts in healthy individuals is lacking in northwest India. Samples from 65 HIV-seronegative healthy volunteers (males, 37; females, 28) aged 18 through 59 years were analyzed using FACS (Fluorescent Antibody Cell Sorter) Count TM System. The values of mean and standard deviation of each lymphocyte subpopulation were estimated. The mean +/- SD of absolute numbers of CD4 and CD8 lymphocytes/microl was 743.4 +/- 307.8 and 541.7 +/- 176.4 in males and 790.7 +/- 280.4 and 497.03 +/- 203.6 in females respectively. The range of CD4 counts was 379 to 1800 in males and 321 to 1265 in females. The mean CD4:CD8 ratio was 1.43 +/- 0.56 in males and 1.78 +/- 0.76 in females. The results of this study show a wide variability in CD4 counts in the Indian population. A large multicentric study would define normal ranges of CD4, CD8, and CD4:CD8 ratios among the Indian population.