Answer to the Letter to the Editor of B. Garg et al. concerning "Drug sensitivity patterns in Xpert-positive spinal tube
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AUTHOR’S REPLY
Answer to the Letter to the Editor of B. Garg et al. concerning "Drug sensitivity patterns in Xpert-positive spinal tuberculosis: an observational study of 252 patients" by Upadhyay M, et al. [Eur Spine J (2020) 29:1476–1482] Jwalant Patel1 Received: 19 August 2020 / Accepted: 25 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
The authors have presented a series of spinal tuberculosis cases with the objectives to assess drug sensitivity patterns in the Xpert MTB-positive spinal TB patients and to frame the guidelines for starting empirical anti-tubercular treatment at the earliest in cases with repeated negative or indeterminate culture results, in an unresponsive patient or places where standard culture and drug sensitivity testing (DST) facilities are not available [1]. Besides the primary drug resistance which is genetically determined, the acquired forms of drug resistance are contributed by the inadequate treatment without weight-adjusted drug dosage regimens, incomplete treatment with short-course chemotherapy without supervision and non-adherence of the patients. The authors do agree and urge the readers of this journal to be up to date with the most recent WHO guidelines [2] that suggest pyrazinamide (Z) as a ‘weakly bactericidal’ and should be considered an essential part of the intensive phase of anti-tubercular therapy not only in drug-susceptible but also in MDR cases [1, 2]. The authors have mentioned that rifampicin and isoniazid are the only bactericidal first-line drugs with most potent bactericidal effects on all populations of organism including intra- and extracellular, dormant organisms and acidic or non-acidic environment, and hence such a resistance pattern adversely affects the outcome, especially in MDR (multi-drug resistant) spinal TB cases. In the most recent guidelines, WHO has suggested that MDR-TB and rifampicin-resistant tuberculosis (RR-TB) should be grouped together for drug-resistant TB [2]. The Xpert test is used for detecting rifampicin resistance; due to close linkage of the isoniazid resistance gene, a positive Xpert test is also * Jwalant Patel [email protected] 1
Mumbai Institute of Spine Surgery, Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India
considered as a surrogate marker for isoniazid resistance. However, authors have shown that not all patients showing rifampicin resistance were found to have isoniazid resistance on drug sensitivity testing (DST) in this series. These findings necessitate the role of individualized treatment and drug regimen based on most commonly prevalent drug sensitivity patterns in the endemic areas as discussed in the study. In addition, the accuracy and efficacy of the Xpert test to detect the rifampicin resistance particularly in the EPTB are low as compared to its efficacy in pulmonary TB as shown in various studies [3]. The reasonable explanations for the discordant findings of this study as compared to the most recent WHO guidelines are that the present study was conducte
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