Light-emitting diode-fluorescent microscopy: Determining its sensitivity and specificity in diagnosis of pulmonary tuberculosis in a high-burden tuberculosis region and resource-limited country like India

Abstract

Background: Tuberculosis (TB) remains a major global health problem. India accounts for the one-fourth of the global TB burden. For resource-limited countries like India having high burden of TB, smear microscopy is the most commonly used method for microbiological diagnosis. Although culture being highly sensitive and specific method, it is time-consuming. Under Revised National TB Control Program (RNTCP), Ziehl–Neelsen (ZN) stain-based microscopy and light-emitting diode-based fluorescent microscopy (LED-FM) are being recommended. Aim: The present study was done to determine the sensitivity and specificity of ZN stain-based microscopy and FM (LED-FM) keeping solid culture as gold standard. Materials and Methods: A total of 1503 sputum samples were collected from suspected cases of pulmonary TB (new or previously treated). They were processed and subjected to ZN (conventional light microscopy), Auramine-O (AO) staining (LED-FM) and solid culture on Lowenstein–Jensen medium for detection of acid-fast bacilli. Positive smears were graded according to RNTCP guidelines. Results: Sensitivity, specificity, positive predictive value, and negative predictive value of ZN staining technique were 84.93%, 95.74%, 96.50%, and 82.16%, respectively, and that of FM was 95.25%, 91.33%, 93.81%, and 93.31%, respectively. Conclusion: LED-FM being more sensitive, especially in detecting the paucibacillary cases and less time-consuming, has advantage over ZN method. Nation-wide implementation will lead to improved diagnosis, thus better control of TB.

Keywords

• Auramine-O
• light-emitting diode-based fluorescent microscopy
• sensitivity
• specificity
• Ziehl–Neelsen