Evaluation of light emitting diode-based fluorescence microscopy for the detection of mycobacteria in a tuberculosis-endemic region.

To evaluate fluorescence microscopy (FM) using light emitting diode (LED) technology for the detection of acid-fast bacilli at a tertiary referral centre in Mumbai, India, a tuberculosis-endemic country.

LED FM was introduced into a laboratory experienced with Ziehl-Neelsen (ZN) microscopy but unfamiliar with FM. It was evaluated in parallel with routine ZN microscopy services and compared with mycobacterial culture as a reference standard.

A total of 1357 pulmonary and 917 extra-pulmonary specimens were examined during the study. LED FM had 78.3% sensitivity and 92.0% specificity against mycobacterial culture when using pulmonary specimens, and 34.0% sensitivity and 88.8% specificity for extra-pulmonary specimens. The mean time per smear examination was 2.48 min for ZN vs. 1.41 min for LED FM. Several biases in study design and operation identified during analysis, which are likely to lead to underestimates of LED FM accuracy, are discussed in the context of future LED FM evaluations.

Although LED FM has significant benefits over both ZN microscopy and conventional FM, its implementation and validation may be prone to difficulties which could hamper evaluation of its performance. Adequate training and detailed standard operating procedures are important to maximise accuracy.

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