LAUSR

Dear Editor, The publication on “Diagnostic performance of GenoType® MTBDRplus line probe assay” by Idrees et al. is very interesting.[1] Idrees et al. concluded that “MTBDRplus detected TB more rapidly and accurately than smear microscopy with significant accuracy for isoniazid (INH) and rifampicin (RMP) resistance. Its use in clinical practice would lead to rapid detection and effective management.”[1] In fact, MTBDRplus can be useful, but there are many considerations. First, the cost of test is an important concern for many laboratories. According to a study from Africa titled, “MTBDRplus line probe assay cost $23.46/sample,”[2] Shah et al. noted that “reference laboratories must balance costs with performance characteristics and the need for rapid results.”[2] We would like to share experience from our countries. The “cost associated with widespread implementation” is a big topic that requires assessment.[3] Due to high cost, some laboratories do not provide the service while others wait to get an appropriate amount of sample for testing. Therefore, the rapid test might not be cost-effective and not economically sounded. Second, the diagnostic property of the test is a big concern. In a recent report from Pakistan, “the major concern with the GenoType® MTBDRplus assay was false-negative results.”[4] Javed et al. reported that “the assay was unable to detect 30 (30/100; 30%) strains resistant to INH and 23 (23/100; 23%) strains resistant to RMP.”[4] The similar diagnostic problem was also reported from Nigeria[5] and China.[6] In another report from South Africa, the sensitivity of MTBDRplus was also lower than other available assays.[7] Recently, Nosova EIu et al. performed a study to compare the performance of MTBDRplus with other available tests and found that TB-Biochip, not MTBDRplus, is the only acceptable molecular assay that was sensitive enough for detection and for revealing multidrug-resistant clinical samples.[8] Therefore, the problem of the accuracy of the diagnosis is still another big problem in using MTBDRplus. Based on these data, without comparison and concern on cost-effectiveness, the conclusion and suggestion to use the MTBDRplus in clinical practice in any setting seems to be too preliminary.