World Health Organization 2018 treatment guidelines for rifampicin-resistant tuberculosis: uncertainty, potential risks and the way forward.

The 2018 World Health Organization (WHO) treatment guidelines for multidrug-/rifampicin-resistant tuberculosis (MDR/RR-TB) give preference to all-oral long regimens lasting for 18-20 months. The guidelines strongly recommend combining bedaquiline, levofloxacin (or moxifloxacin) and linezolid, supplemented by cycloserine and/or clofazimine. The effectiveness of this combination in a long regimen has not been tested in any study to date, with corresponding uncertainty. The guidelines indicate that, ideally, all MDR-TB patients should have - as a minimum - the isolate tested for fluoroquinolones, bedaquiline and linezolid susceptibility before the start of treatment. Unfortunately, the capacity for drug susceptibility testing is insufficient in resource-limited settings. The risk of acquired bedaquiline resistance cannot be ignored, especially in patients with undetected resistance to fluoroquinolones. Both linezolid and cycloserine are known for their high frequency of serious adverse events. The combination of bedaquiline, moxifloxacin and clofazimine in the same regimen may excessively increase the QT interval. These expected adverse effects are difficult to monitor and manage in resource-limited settings, and may result in frequent modifications and a less effective regimen. The final STREAM results have confirmed the non-inferiority of the short regimen compared with the long regimen. Before evidence on the all-oral long and modified all-oral short treatment regimens is available, the WHO-recommended short MDR-TB regimens, with monitoring for ototoxicity, remain a better treatment option for the management of MDR/RR-TB patients who are eligible for short regimens in low- and middle-income countries. National tuberculosis programmes should also strengthen their capacity in the detection and management of fluoroquinolone-resistant MDR-TB following the WHO guidelines.