Evaluation of GeneXpert MTB/RIF and line probe assay for rapid diagnosis of Mycobacterium tuberculosis in Sudanese pulmonary TB patients
Authors: Rahma Hasbelrasoul Ali, Nuha Yousif Ibrahim, Asrar Mohamed Abdalsalam Elegail2, Naziha Abdelrhman Mohamed Eltohami, Rasha Sayed Mohammed Ebraheem, Salma Faroug Mohammed Ahmed2, Huda Hassan Howaytalla Ahmed, Eman Osman Mohamed Nour, Muataz Mohamed Eldirdery, Hassan Hussein Musa
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Objective: To study the sensitivity and specificity of line probe assay (LPA) and GeneXpert
compared with drug susceptibility test (DST).
Methods: A cross-sectional study was conducted for 126 TB patients in Sudan. Mycobacterium
tuberculosis was identified by drug susceptibility test. The smear-positive sputum specimens
were screened for rapid detection of resistance to rifampicin (RIF) and isoniazid (INH) by
molecular LPA and GeneXpert assay.
Results: 67.5% of patients were male, 19.8% were new cases, 57.1% were previously treated
TB patients, and 64.3% of the affected patients were in the age group of 16–30 years. About
32.5% of samples were MDR by both DST and LPA, 66.7% were sensitive by both DST and
LPA, and 0.79% were MDR by DST and sensitive by LPA. However, 36.51% of samples
were MDR by both DST and GeneXpert, and 63.49% were sensitive by both DST and
GeneXpert. There was no significant difference between DST and LPA technique (P = 0.50).
The sensitivity, specificity, positive predictive value and negative predictive value of LPA were
97.6%, 100%, 97.6%, and 100%, respectively; while for GeneXpert, they were 100%, 100%,
100% and 100%, respectively. The RIF resistance was associated with mutation in the region
of rpoB 530-533, mostly S531L mutation, and the most INH resistant samples (98.58%) were
linked with KatG gene and codon 315 (S315T1).
Conclusions: The molecular assays are the best screening tools for MDR TB, which may
exceed TB diagnoses.