Performance of light-emitting diode fluorescence microscope for diagnosis of tuberculosis

Fluorescence microscopy (FM) over the years has shown the potential for increasing the performance of microscopy. The present study was aimed to access the performance of the LED microscope for the detection of acid fast bacilli in a tuberculosis (TB) endemic country.

The study was conducted at a National Reference Laboratory (NRL) in New Delhi, India. Sputum samples were collected from suspected TB patients. Each sample was processed with Auramine O and ZN methods. Auramine O stained smears were evaluated using two different excitatory light sources (MVP and LED); and ZN stained smears were examined under light microscope. The mean time required to read the smears with different modalities was recorded. Bacterial cultures provided the reference standard.

A total of 200 patients were included in this study. Sensitivity and specificity for the LED assessment, MVP assessment and light microscopy were 83.1% and 82.4%, 78.5% and 87.5% and 81.6% and 83.5%, respectively. Mean reading time was approximately three times faster than ZN microscopy. The mean time to read a negative smear was 2min with fluorescence microscopy and 5min with light microscopy with time savings of 60%.

Although the use of LED-FM only marginally increased sensitivity, the considerable time saving ability combined with very good acceptance and ease of use makes it a reliable alternative to other conventional methods available.