Sensitivity of Ziehl-Neelsen Stain Compared with Polymerase Chain Reaction in the Diagnosis of Pulmonary Tuberculosis

Abstract

Simple, rapid, and sensitive methods that enhance the detection of Mycobacterium tuberculosis (M. tuberculosis) from sputum specimens are needed. This study compared the sensitivity of ZN stain and polymerase chain reaction (PCR) in the detection of M. tuberculosis from sputum specimens to achieve early and proper diagnosis in order to start accurate regimen. this is a cross-sectional laboratory-based study in which ١٧١ sputum specimens were collected from patients suspected of having pulmonary tuberculosis attending Abu-Anga Teaching Hospital, El Sha’ab Teaching Hospital and the Tuberculosis Reference Laboratory at the national Health Laboratory in Khartoum, Sudan, during the period from January to March 2010. Sputum specimens were examined using Ziehl-Neelsen stain; all sputum specimens extracted by Isopropanol method to obtain DNA and subjected to PCR amplified IS6110 insertion sequence in terms of sensitivity. At same time all sputum specimens were inoculated in Lowenstein Jensen (LJ) media and incubated at 37°C. Only 37(22%) were acid fast bacilli positive, whereas 145(85%) were PCR positive with bands typical to the target sequence of IS6110 as showed by the standard DNA marker, Ziehl-Neelsen technique sensitivity was found to be ٢٦% compared to PCR assay. Concerning cultivation of all sputum specimens on LJ media there were only 23.4% showed MTC-like colonies in LJ media (dry, rough and pale yellow), whereas 5.8% were considered rapidly growing Mycobacterium, and 70.8% samples revealed contamination or no growth. Further biochemical tests were used beside colonial morphology in order to confirm the existence of Mycobacterium tuberculosis complex. The study concluded that though the sensitivity of ZN stain was quietly decreased, PCR assay provides a significant improvement in diagnosis of pulmonary tuberculosis.