Abstract:

Objective To study the practicability of light-emitting diode (LED) fluorescence microscope in laboratory staff to examine Mycobacterium.Methods A total of 3770 newly diagnosed TB suspected patients were continuously included from eight county-level TB dispensaries of Heilongjiang from July 2017 to October 2018. Each patient provided 2-3 sputum specimens, and 9079 examples were analyzed and cultured. The laboratory staff prepared two sputum smears for each sample. Ziel-Nelson (Z-N) and fluorescence staining for the smear were conducted, respectively. Then traditional light microscopes and LED fluorescence microscopes were used for microscopic examination. At the same time, reading time and smear preservation were recorded and analyzed.Results The positive rates of traditional light microscopy and LED fluorescence microscopy were 11.41% (430/3770) and 12.79% (482/3770); the positive detection rate of simple method of solid culture was 17.14% (646/3770), the difference was statistically significant (χ ²=5602.10, P<0.01). Using culture test as the standard, the sensitivity of microscopy by traditional light microscope and LED fluorescence microscope was 61.46% (397/646) and 66.72% (431/646), and the specificity was 98.94% (3091/3124) and 98.37% (3073/3124), respectively. Youden index of traditional light microscope and LED fluorescence microscope was 0.604 and 0.651. The reading time of LED fluorescence microscope ((184.33±52.22)s) was obviously lower than that of traditional light microscope ((291.21±95.40)s), and the difference was statistically significant (F=5670.80, P<0.01). 1179 positive fluorescent staining smears with different positive grades detected by LED fluorescence microscopy were putted in the opaque glass box at room temperature (22-25℃), and avoided direct sunlight. Five qualitative errors and 10 quantitative errors were found after 4 months of storage.Conclusion The efficiency of LED fluorescence microscopy in detecting acid-fast bacilli is better than that of ordinary optical microscopy. It shortened the film reading time of the staff. The stained glass slides can be stored in the glass box that avoids direct sunlight at room temperature, which is suitable for promotion and application in the basic laboratory.

Key words: Mycobacterium tuberculosis, Microscopy, fluorescence, Sensitivity and specificity, Evaluation studies