Comparison of GeneXpert and Line Probe Assay for Detection of Mycobacterium tuberculosis and Rifampicin-Mono resistance at the National Tuberculosis Reference Laboratory, Kenya

Abstract

Introduction The dual challenge of low diagnostic sensitivity of microscopy test and technical challenge of performing a TB culture test poses a problem for case detection and initiation of Tuberculosis (TB) second-line treatment. There is thus need for a rapid, reliable and easily accessible assay. This comparative analysis was performed to assess diagnostic performance characteristics of GeneXpert MTB/RIF and Line Probe Assay (LPA) Methods 329 sputum samples of patients across the 47 counties in Kenya suspected to have drug resistant TB were picked and subjected to GeneXpert, LPA and Culture MGIT at the National TB Reference Laboratory. Sensitivity, specificity and predictive values were then determined to assess the performance characteristics of various assays. Results GeneXpert had a sensitivity, specificity, positive predictive value, and negative predictive value of 78.5%, 64.9%, 59.4% and 82.2% respectively while LPA had 98.4%, 66.0%, 65.4% and 98.4%. For diagnosis of rifampicin mono-resistance GeneXpert had a moderate agreement (Kappa=0.59, P<0.01) (sensitivity= 62.50%, specificity = 96.50%) while LPA that had almost perfect agreement (Kappa= 0.89, p<0.01) with a (sensitivity= 90.0% and specificity= 99.1%). Conclusion LPA has a better performance characteristic to GeneXpert and an alternative to culture with regards to detection of RIF’s mono-resistance.

Phenotypic and genotypic drug sensitivity profiles of Mycobacterium tuberculosis infection and associated factors in northeastern Ethiopia

“…Such difference between the two ndings might be due to the difference in number of drug resistant isolates. Further, the agreement between Culture MGIT and LPA in detecting katG, inhA and both (katG and inhA) resistance was almost perfect and agrees with a study from Kenya [22].…”

“…In the case of freezed live Mycobacterium, its survival could be interrupted through time until it was sub-cultured using the MGIT instrument. The higher sensitivity result 94.2% of LPA and its lower speci city value 30.2% is comparable with similar settings done in Kenya where its sensitivity and speci city was 99.2 and 26.9%, respectively [22]. This showed that LPA has a good performance in detecting the true positivity of Mycobacterium and in a fair agreement (Kappa = 0.276; P < 0.001) with the BACTEC MGIT 960 performance.…”

Pattern of Multi-Drug Resistant Tuberculosis in HIV Sero Positive Patients in Rivers State Nigeria

“…The variations observed in this study may have resulted from differences in diagnostic methods. Line probe assays reportedly have a higher sensitivity and specificity in detection of drug resistant Mycobacterium tuberculosis in comparison to GeneXpert and Sputum Acid-Fast Bacilli which are still the most frequently used diagnostic methods in many centers across southern Nigeria [8,17,30]. Therefore, TB and DRTB cases which would have been missed with other diagnostic methods may have been detected in this study.…”

“…One of these methods, the molecular line probe assay [LPA], GenoType®MTBDRplus, developed by HAIN Lifescience, Nehren, Germany for the molecular genotypic identification of MTBC and its resistance to rifampicin [RIF] and and/or isoniazid [INH] directly from clinical specimens as well as culture was approved in 2008 [15]. The use of LPA has improved the detection and treatment of drug resistant TB globally [16,17] via early and accurate diagnosis, with significantly lesser turnaround time [48 hours] as compared to conventional DST method [42 days]; thus enabling appropriate medication for treatment, especially in the presence of drug resistance, with a resultant break in the transmission cycle.…”