Line probe assay, a rapid and efficient test for the diagnosis of multidrug-resistant tuberculosis in Egypt

Background Earlier detection of tuberculosis (TB) and multidrug-resistant tuberculosis (MDR-TB) is crucial to preclude TB. We examined a genotypic drug sensitivity testing method for drug-resistant TB diagnosis using the line probe method as a rapid and technically simple method. The test used mutation-specific probes to determine isoniazid (INH) and rifampin resistance (RIF). Patients and methods The study was carried out on 82 Mycobacterium tuberculosis isolates that were identified phenotypically as MDR-TB isolates. The GenoBlot assay was assessed for fast detection of both rifampicin (RIF) and INH resistance against conventional phenotypic anti-TB drug sensitivity testing. The results were contrasted with the phenotypic drug susceptibility testing (DST) results of targeted samples; the turnaround time for both methods was evaluated. Results Compared with classical DST on solid media (Lowenstein Jensen), the line probe assay (LPA) technique had a relatively high concordance rate. The sensitivity to rifampicin was 94 and 91.5% for INH, and both showed 100% specificity. The consumed time for results by LPA was 24–48 h, while required 26 days for phenotypic culture on solid media and a supplemental 44 days for phenotypic DST. Conclusion LPA is a rapid, sensitive, easy to use, and efficient genotypic DST for MDR-TB detection.