Abstract: Objective  To evaluate the application effects of fluorescent microscopes with light-emitting diodes (LED-FM) in detecting Mycobacterium tuberculosis (Mtb) in sputum samples in laboratories based basic-level. Methods  One thousand seven hundred and thirty-eight sputum samples were collected from 592 pulmonary tuberculosis (TB) suspects who were detected by seven county TB dispensaries in Xining city of Qinghai province from July 2011 to September 2011. Two smears were prepared for each sputum specimen and then stained by Ziehl-Neelsen and auramine O respectively. The smear specimens stained by Ziehl-Neelsen were read by using conventional light microscope (CLM) while the specimens stained by auramine O were read by using LED-FM, and the results were recorded. Culture on solid Lowenstein-Jensen (L-J) media was also performed for all collected sputum samples and the culture result was used as a gold standard for comparison of smear-positive rate tested by two different types of microscopes; the veracity of diagnosis and diagnosis time by using the two methods were also compared.  Results  The smear-positive rate was 14.90% (259/1738) by using LED-FM, which was 1.15% higher than that of 13.75% (239/1738) by using CLM (Z=5.88, P<0.05). With L-J culture as the gold standard, the sensitivity, specificity and the area under the curve (AUC) of CLM in detecting TB patients were 79.60% (199/250; 95%CI＝74.60%-84.60%), 97.31% (1446/1486; 95%CI＝96.49%-98.13%) and 0.8878 (95%CI＝0.8623-0.9133); the sensitivity, specificity and AUC of LED-FM were 84.80% (212/250; 95%CI=80.30%-89.25%), 96.84% (1439/1486; 95%CI＝95.95%-97.73%) and 0.9118 (95%CI＝0.8890-0.9347). The reading time by LED-FM and CLM was (144.19±62.173) s and (185.600±79.271) s respectively; the difference of the reading time was significant (t=15.32, P<0.01).  Conclusion  If LED-FM is used for TB diagnosis, the smear-positive rate of sputum samples can be increased significantly. Compared with CLM, LED-FM has higher sensitive and similar specificity in detecting TB patients. So it is concluded that the application of LED-FM has higher value in detection of pulmonary TB, and it can also shorten the reading time of sputum smear slides.

Key words: Mycobacterium tuberculosis, Microscopy, fluorescence