Development and evaluation of 'Quick TB DNA Extraction' kit for the rapid and efficient detection of multidrug-resistant tuberculosis from sputum transported on bio-safe filter.

PURPOSE: We recently demonstrated the utility of the 'TB Concentration & Transport' kit for bio-safe, ambient-temperature transport of dried sputum samples on Trans-Filter, along with the 'TB DNA Extraction' kit for efficient DNA extraction from Trans-Filter for use in the Line Probe Assay (LPA) for diagnosing drug-resistant tuberculosis (TB). The present study aimed to develop and evaluate a new 'Quick TB DNA Extraction' kit ('Quick DNA' kit) for rapid DNA isolation from Trans-Filter samples and assess its compatibility with LPA for the detection of multidrug-resistant TB (MDR-TB).

METHODS

Consecutive presumptive TB/MDR-TB/XDR-TB patients (n = 1823) were screened using LED-FM and/or TBDetect microscopy at 2 Designated Microscopy Centres associated with the National Institute of Tuberculosis and Respiratory Diseases (NITRD), New Delhi. Smear-positive samples (n = 235) were processed in duplicate using the 'TB Concentration and Transport' kit. Dried sputum on bio-safe Trans-Filters was transported at ambient temperature, along with sputum samples, in a 3-layer packing in cooling conditions to NITRD Hospital (a National Reference Laboratory). DNA was extracted from Trans-Filters using 'Quick DNA' kit and the 'TB DNA Extraction' kit, and from sputum using Hain's GenoLyse® DNA Extraction kit for first-line LPA for MDR-TB detection.

RESULTS

Quick Kit-LPA and Kit-LPA (LPA with DNA extracted from Trans-Filter using 'Quick DNA' kit and 'TB DNA Extraction' kit, respectively) showed similar sensitivity of 88.9% (95% CI: 65.3-98.6) and 88.5% (95% CI: 69.9-97.5) and specificity of 100% (95% CI: 98.2-100) and 99.5% (95% CI: 97.3-99.9) for rifampicin and isoniazid resistance detection, respectively against Direct-LPA (LPA with DNA extracted from sputum samples using GenoLyse kit). User feedback obtained from laboratory technicians corroborated that the one-step 'Quick DNA' kit procedure was rapid (5 minutes), easy to perform, seamlessly integrated with LPA testing, and was suitable as a replacement for Kit-LPA or Direct-LPA.

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CONCLUSION

The gap between drug-resistant TB detection and treatment initiation can be narrowed through Universal-Drug Susceptibility Testing by implementing (i) bio-safe and ambient temperature transport of sputum from primary healthcare centres to central laboratories, and (ii) by using Quick Kit-LPA over Direct-LPA in patients residing in remote areas.