COMPARISON OF XPERTMTB/RIF AND GENOTYPE MTBDRPLUS ASSAYS IN THE DETECTION OF TUBERCULOSIS AND RIFAMPICIN RESISTANCE AMONG RETREATMENT SAMPLES IN KENYA

Background: Tuberculosis (TB) is a major public health problem globally. The National TB program in Kenya has adopted number of new TB diagnostic tools. The present study investigated the performance of XpertMTBRIF and GenoTypeMTBDRplus in the diagnosis of Tuberculosis and rifampicin resistance among retreatment cases. Methods: A total of 561 TB retreatment sputum samples were subjected to XpertMTBRIF, MGIT culture and GenoTypeMTBDRplus assays. Thereafter, their performance in diagnosis of Mycobacterium tuberculosis and detection rifampicin resistance was compared. The sensitivity and specificity of the tests were determined and Receiver operating characteristic (ROC) analysis was performed to compare the diagnostic tools. Results: The area under the curve (AUC) for XpertMTBRIF MTB detection was 0.81 while that of LPA was 0.85. The AUC for Rifampicin resistance detection was 0.95 and 0.83 for XpertMTBRIF and GenoTypeMTBDRplus respectively. The sensitivity of XpertMTBRIF assay in the detection of MTB was 86.2% while the specificity was 74.9%. GenoTypeMTBDRplus exhibited a sensitivity of 87.8% and the specificity was 84%. On the other hand, XpertMTBRIF exhibited a high sensitivity (91.7%) and specificity (98.5%) in the detection of Rifampicin resistance. GenoTypeMTBDRplus had a sensitivity and specificity of 66.7% and 98.9% respectively. Comparison of the areas under the curve (AUC) for both tests revealed that there is no significant difference (p=0.16, p>0.05) in the detection of MTB as well as Rifampicin resistance (p=0.9, p>0.05). Conclusion: Based on the findings of this study the sensitivity and specificity of the two diagnostic tests, we recommend the use of XpertMTBRIF for surveillance since its reagents and operationalization costs are easy to implement.