If we are to eliminate tuberculosis (TB) in Nunavut by 2030, we need to increase certain medical activities within affected communities on a proactive and regular basis over a number of years. One of these activities is the diagnosis and treatment of latent TB infection (LTBI, also known as ‘sleeping TB’) .
Expansion of LTBI diagnosis and treatment is supported by the World Health Organization (WHO), whose EndTB Strategy (2014) states that “ending the TB epidemic will require the elimination of this pool of [latent TB] infection”. More specifically, one of WHO’s EndTB Strategy documents states that “management of LTBI in people with a high risk of developing active TB could be an essential component of TB elimination, particularly in low TB-incidence countries.”
LTBI is most commonly diagnosed using Tuberculin skin testing (TST), which is a test that can be performed by a nurse in even the most remote community. Someone having a positive TST result is then considered for treatment that can help to prevent the development of active/infectious TB, which is important because active/infectious TB cases allow the TB germ to spread to other people. Preventing new cases of active/infectious TB helps to break the cycle of TB transmission. The WHO has communicated that such TB preventive treatment, when given to people at the highest risk of progressing from TB infection to disease, remains a critical intervention to benefit individuals and communities alike.
However, there are several challenges associated with the expansion of LTBI diagnosis and treatment. Firstly, although we know that certain groups of people with LTBI are more likely to go on to develop active/infectious TB disease, it is not possible to predict exactly which individuals will. Groups at highest risk of developing active TB include:
– those having recent contact with someone having active TB, especially young children with weakened immune systems
– recent converters, i.e. people who have recently gone from TST-negative to TST-positive miners exposed to silica dust
– those with nutritional deficiencies
But limiting LTBI diagnosis and treatment to individuals in the above ‘risk groups’ over the past few decades has not led to a reduction in TB rates in Nunavut. In fact, things have gotten worse within the territory, not better. Because of this, we should consider implementing more aggressive and innovative LTBI diagnostic strategies in those communities within Nunavut that continue to suffer from high rates of active TB.
Expanded diagnosis and treatment of LTBI has been performed in the past and with some success. Dehghani et al (2018) reported that population-based LTBI screening and treatment, i.e. offering TST to an entire population rather than just to individuals with certain risk factors, was associated with a significant decrease in TB rates in Indigenous populations in Canada, USA, and Greenland between 1960 and 1980.
A second challenge relates to the drugs used to treat LTBI, as these can sometimes result in severe side effects. Older individuals and those with pre-existing liver disease are some of those at higher risk of such side effects. Campbell et al (2019) argue that we face a choice between the current patient-centred approach that values shared decision-making (but will not achieve TB elimination) versus a utilitarian approach that tolerates individual net harm to advance public health goals. “TB elimination in low-incidence countries will require extensive screening and treatment of LTBI, including in people for whom the harms of LTBI treatment outweigh the likely benefits”.
When it comes to side effects from LTBI treatment, it might help to look at things from a different perspective: entire families and communities suffer from the detrimental effects of TB, not just individuals. For that reason, an important group to consider testing and treating for LTBI are those who, if they did develop active TB, would place vulnerable contacts at risk. Thus, anyone whose work brings them into regular contact with young children and the elderly, such as those employed to perform community programs, should be offered TST on a regular basis.
Normally before health care workers offer any medication to a person, a risk vs. benefit analysis is performed. Fortunately, a shorter medication regimen is now available for those with LTBI, which has fewer adverse effects and thereby improves the risk: benefit ratio in favour of the latter. This newer regimen involves taking 2 different medications (rifapentine and isoniazid) once weekly for 3 months (so commonly abbreviated as ‘3HP’) is now available in limited settings in Canada. A recent study by Alvarez et al (2020) supports the feasibility and safety profile of 3HP for the treatment of LTBI in Nunavut.
A third challenge related to the expansion of LTBI treatment is ensuring that people ultimately complete the medication regimen. Pease et al (2019) reported that older individuals and those identified via employment screening were at highest risk of not completing LTBI treatment. Thus, a number of people on LTBI treatment will require adherence support.
But how best to actually expand LTBI diagnosis and treatment within Nunavut? WHO’s EndTB Strategy mentioned above makes it clear that there should be plenty of community involvement: “The affected communities must also be a prominent part of proposed solutions. Community representatives and civil society must be enabled to engage more actively in programme planning and design, service delivery, and monitoring, as well as in information, education, support to patients and their families, research, and advocacy. To this end, a strong coalition that includes all stakeholders needs to be built.”
More on this in another blog…
 The Nunavut TB Manual defines LTBI as “the presence of infection with TB bacteria, without evidence of clinically active TB. Clients with LTBI have no TB symptoms, no evidence of radiographic changes that suggest active TB, and negative TB smears and cultures. LTBI is not infectious.”
Photo bySeeChange Initiative