Tuberculosis (TB)

WHO issues recommendations on management of isoniazid-resistant tuberculosis

Within the context of an ongoing extensive review of evidence on treatment of drug-resistant (TB) taking place in 2018, the World Health Organization (WHO) has issued a Supplement to its current drug-resistant TB treatment guidelines, providing recommendations for the management of isoniazid-resistant TB [1]. These will be incorporated into the Consolidated Guidelines for Treatment and Care of Drug-resistant TB envisaged by WHO later in 2018. [2, 3].

Isoniazid-resistant TB, without concurrent rifampicin resistance, is estimated to occur in about 8% of people with TB globally [4]. A new regimen without injectable agents, and which combines rifampicin, ethambutol, pyrazinamide and levofloxacin, is now recommended in adults and children diagnosed with this type of drug-resistant TB.

“Isoniazid is one of the essential medicines to treat TB and once resistance develops patients are at greater risk of having poor treatment outcomes” said Dr Tereza Kasaeva, Director of the WHO Global TB Programme. “Providing targeted and more effective treatment to these patients will help reduce death and suffering, in line with the objectives of the WHO End TB Strategy.”

The recommendations for treatment of isoniazid-resistant TB anticipate the most common situations that practitioners would face and provide practical options when deciding on clinical management, including patient selection, what to do while awaiting drug-susceptibility test results, and principles to prevent development of additional resistance to other medicines.

Accurate diagnosis of isoniazid resistance, excluding rifampicin resistance and identifying patients most at risk are key interventions for successful implementation of the recommended regimen. Molecular methods to identify the specific mutations responsible for isoniazid resistance are available yet still out of reach for many patients, given that these tests need sophisticated laboratory infrastructure and specialised training.

“New advances in research and technology mean that precision-medicine is increasingly becoming possible in the management of drug-resistant TB” said Dr Karin Weyer, Coordinator of Laboratories, Diagnostics & Drug Resistance at the WHO Global TB Programme. “Patients should receive the best possible treatment for their specific TB disease. Ensuring that treatment is informed by timely and quality-assured drug susceptibility testing is a key aspect of universal health coverage and rapid, user-friendly tests close to patient care are urgently required”.

Isoniazid-resistant TB, without concurrent rifampicin resistance, occurs widely throughout the world although the vast majority of patients with TB have drug-susceptible disease. The global level of isoniazid resistance is still below 10%, however, in some regions, the proportion of cases that present to health care services with strains showing isoniazid resistance can be much higher, according to the latest findings from the WHO Global Anti-TB Drug Resistance Surveillance Programme [4].

The new isoniazid-resistant TB treatment recommendations will also be incorporated into the updated Companion Handbook to the WHO guidelines for the programmatic management of drug-susceptible and drug-resistant tuberculosis. Ahead of the 2018 update of this Handbook, additional information guiding the implementation of these recommendations is presented in a document on Frequently Asked Questions document [5].