Mycobacterial Diseases
Open Access

Abstract

The Yield of Sputum Smear Direct Microscopy Using Ziehl-Neelsen Stain in Comparison with Lowenstein Jensen Culture on the Diagnosis of Pulmonary Tuberculosis in Tripoli-Libya

Ahmed Shoukrie, Ahmed Alameen, Doha Shaban, Wedad Alamari, Naima Aboguttaia, Nabil Askar, Ali Torki and Mohamed Furjani

Background: In the developing countries, Tuberculosis is one of leading causes of morbidity and mortality. The detection and identification of Mycobacterium tuberculosis is considered a great challenge for clinical microbiologists. Albeit Ziehl-Neelsen (ZN) smear is being a rapid diagnostic tool for TB, the culture on Lowenstein Jensen (LJ) medium is considered the golden diagnostic tool for TB in the developing countries.

Objectives: To evaluate the validity and reliability of ZN smear of acid-fast bacilli compared to the culture on LJ medium.

Design and Settings: This study is the first in Libya which was conducted from January 2016 to December 2016 in the TB reference laboratory at the National Center for Disease Control (NCDC), Tripoli, Libya.

Patients and methods: The retrospective analytic comparative cross-sectional study included patients visiting TB OPD clinic at NCDC, including transferred patients from other healthcare facilities and hospitals. A total of 2783 specimen of suspected pulmonary TB cases were processed for both direct smear and culture. The direct smears were stained with ZN method (1% Carbolfuchsin, 3% Hydrochloric acid Ethanol and 0.1% methylene blue). Specimens were observed under 100-x oil immersion lens, whilst cultures were inoculated on LJ medium after digestion and decontamination of the clinical specimens.

Results: Of total 2783 study subjects, 203 (7.29%) were smear positive while 327 (11.74%) were culture positive. Out of 203 smear positive pulmonary cases, 154 (47.094%) were found to be positive on LJ culture. A total of 2407 pulmonary cases were negative on the smear and LJ culture for Mycobacterium tuberculosis.

Conclusion: This preliminary study indicated the low sensitivity of sputum smear direct microscopy for early diagnosis of TB, while culture on LJ remains the golden standard modality.