Evaluation of GeneXpert MTB/RIF system performances in the diagnosis of extrapulmonary tuberculosis

Abstract

BackgroundTuberculosis represents a serious public health problem and a significant diagnostic and therapeutic challenge worldwide. Molecular diagnostic techniques are crucial in the World Health Organization’s new tuberculosis control strategy.This study aims to evaluate the performance of GeneXpert MTB/RIF (Cepheid Sunnyvale, CA, United States) in diagnosis of extra-pulmonary tuberculosis then compare it’s performance in detecting Rifampicin resistance to GenoType MTBDRplus (HAIN Life Sciences, Nehren, Germany).MethodsSamples from pulmonary and/or extra-pulmonary origins were analysed in a 21 months retrospective study. Samples were sent to the bacteriology laboratory for Mycobacterium tuberculosis detection using conventional bacteriological and molecular methods (GeneXpert MTB/RIF and MTBDRplus). Sensitivity and specificity were calculated for the stained smear and GeneXpert according to culture (Gold Standard) as well as for GeneXpert MTB/RIF in both negative and positive microscopy tuberculosis cases. Data’s statistical analysis was performed with SPSS13.0 software.ResultsSeven hundred fourteen patients’ samples were analysed; the average age was 47.21 ± 19.98 years with a male predominance (66.4%). Out of 714 samples: 285 were from pulmonary and 429 were from extra-pulmonary origins. The positivity rates for microscopy, GeneXpert MTB/RIF and culture were 12.88, 20.59 and 15.82%, respectively. These rates were 18.9, 23.85 and 20.35% for pulmonary samples and 9.71, 18.41 and 12.82% for extra-pulmonary samples, respectively. The sensitivity and specificity of GeneXpert MTB/RIF were almost the same in both pulmonary and extra-pulmonary samples (78.2 and 90.4%) and (79,3 and 90.3%) respectively.Rifampicin resistance rate found by GeneXpert MTB/RIF was 0.84%. Comparison of Rifampicin resistance obtained by GeneXpert MTB/RIF and Genotype MTBDRplus, showed 100% agreement between the two techniques for studied samples.ConclusionsThis confirms GeneXpert MTB/RIF advantage for tuberculosis diagnosis, particularly extra-pulmonary tuberculosis with negatively stained smear. The performance of GeneXpert and Genotype MTBDRplus are similar in detection of Rifampicin resistance. However, variability of detection performance according to tuberculosis endemicity deserves more attention in the choice of screening techniques of Rifampicin resistance, hence the interest of conducting comparative studies of detection performance under low and medium endemicity on large samples of tuberculosis populations.

Utility of the GeneXpert Mycobacterium tuberculosis/Rifampin (MTB/RIF) Assay on Paraffin-Embedded Biopsy Tissue Samples for Detecting Tuberculosis; Comparison With Histopathology

“…In our study, we noted the detection rate of 26.3% for biopsy specimens diagnosed with TB on routine histopathology. A study including 714 cases of pulmonary and extra-pulmonary TB samples concluded that the detection rates of MTB by GeneXpert assay were 23.85% and 18.41%, respectively, for pulmonary and extra-pulmonary samples [ 7 ].…”

Diagnostic utility of GeneXpert MTB/RIF assay versus conventional methods for diagnosis of pulmonary and extra-pulmonary tuberculosis

“…The diagnosis of EPTB remains challenging for both the clinicians and microbiologists. Nevertheless, the difficulty to gain access to specific sampling sites results in paucibacillary samples and reduces the sensitivity of conventional diagnostic tools [3].…”

Bifocal Tuberculosis with Adalimumab Revealed by Laryngeal Involvement: Case Report

“…GeneXpert is recommended by the World Health Organization in the pulmonary and extra-pulmonary tuberculosis diagnosis in both immunocompetent and immunocompromised patients [8,9]. It is a rapid molecular test with high performance (sensitivity and specificity) [10].…”