Evaluation of molecular detection of extrapulmonary tuberculosis and resistance to rifampicin with GeneXpert super( registered ) MTB/RIF

• Published in: Médecine et maladies infectieuses Vol. 46; no. 1; pp. 20 - 24
• Main Authors: Marouane, C, Smaoui, S, Kammoun, S, Slim, L, Messadi-Akrout, F
• Format: Journal Article
• Language: English
• Published: 01-02-2016
• Subjects: Mycobacterium tuberculosis
• ISSN: 0399-077X
• DOI: 10.1016/j.medmal.2015.10.012

Objective: We aimed to evaluate the GeneXpert super( registered ) MTB/RIF test for the diagnosis of extrapulmonary tuberculosis. The test simultaneously detects Mycobacterium tuberculosis complex and resistance to rifampicin. Methods: We analyzed 153 clinical samples collected in a tertiary hospital in Sfax, Tunisia, between 2013 and 2014. We performed the GeneXpert super( registered ) test, a Ziehl-Neelsen and auramine-rhodamine staining, conventional culture on MGIT 960 and LJ media, and we tested the resistance to anti-tuberculosis drugs on MGIT 960 and LJ media for each sample. Diagnosis was based on clinical, radiological, microbiological, pathological, and therapeutic data. Results: We considered that 59 patients out of 153 presented with tuberculosis. PCR was positive in 50 samples and all of these samples were susceptible to rifampicin. Sensitivity, specificity, positive predictive value, and negative predictive value of the GeneXpert super( registered ) test were 84.7%, 96.8%, 94.3%, and 91%, respectively, compared with diagnosis. We observed a statistically significant difference between the direct test and the GeneXpert super( registered ) test, and between culture and the GeneXpert super( registered ) test. No statistically significant difference was observed between pathological results and the GeneXpert super( registered ) test. Sensitivity of the GeneXpert super( registered ) test was 87.5% in biopsies, 80% in pus and abscesses, and 66.7% in biological fluids. All strains were susceptible to rifampicin with culture and GeneXpert super( registered ) test. Conclusion: The GeneXpert super( registered ) test helped detect a higher proportion of M. tuberculosis complex. It does not replace conventional diagnostic methods but it is a useful addition to achieve better sensitivity and obtain rapid results. Resume Objectif Evaluation du GeneXpert super( registered ) MTB/RIF pour le diagnostic de la tuberculose extra-pulmonaire : detection du complexe Mycobacterium tuberculosis et de la resistance a la rifampicine. Methodes Nous avons analyse 153 echantillons cliniques recueillis entre 2013 et 2014 au laboratoire d'hygiene de Sfax, Tunisie. Pour chaque echantillon, un test GeneXpert super( registered ), une coloration de Ziehl-Neelsen et une coloration a l'auramine, une culture sur milieux MGIT 960 et Lowenstein-Jensen (LJ) et une etude de la sensibilite aux antituberculeux sur milieux MGIT 960 et LJ ont ete effectues. Le diagnostic a ete etabli au vu des donnees cliniques, radiologiques, microbiologiques, anatomopathologiques et therapeutiques. Resultats Nous avons considere que 59 patients sur 153 etaient atteints de tuberculose (TB). La PCR etait positive pour 50 echantillons et ces derniers etaient tous sensibles a la rifampicine. La sensibilite, la specificite, la valeur predictive positive et la valeur predictive negative du GeneXpert super( registered ) etaient respectivement de 84,7 %, 96,8 %, 94,3 % et 91 % par rapport au diagnostic. La difference entre l'examen direct et le GeneXpert super( registered ) etait statistiquement significative. Il en allait de meme pour la culture et le GeneXpert super( registered ). Aucune difference significative n'a ete observee entre l'anatomopathologie et le GeneXpert super( registered ). La sensibilite du GeneXpert super( registered ) etait de 87,5 % pour les biopsies, 80 % pour les pus et abces et 66,7 % pour les liquides biologiques. Toutes les souches etaient sensibles a la rifampicine en utilisant la culture et le GeneXpert super( registered ). Conclusion: L'utilisation du GeneXpert super( registered ) augmente la sensibilite de detection du complexe M. tuberculosis. Il ne remplace pas les methodes classiques de diagnostic mais les complete afin d'obtenir une meilleure sensibilite et des resultats plus rapides.