Cost effectiveness of latent tuberculosis screening among asylum seekers in Stockholm

Abstract

Introduction: The burden of tuberculosis (TB) in Sweden is concentrated among migrants from high TB incidence countries. The incident cases in Sweden arise mainly through reactivation of a latent tuberculosis infection (LTBI) acquired in the home country or during transit. Progression from LTBI to active TB disease can be prevented through treatment with anti-tubercular medicines. LTBI screening is therefore offered for asylum seekers and refugees in Sweden as part of a voluntary health examination (HE). Little is known about their experiences of LTBI screening and treatment. In addition, there has been no previous evaluation of the cost-effectiveness of the current LTBI screening policy in Stockholm or Sweden.

Aims: The overarching aim of this thesis was to determine the cost-effectiveness of the current strategy of screening for LTBI among asylum seekers in Stockholm. This aim was achieved through the following specific objectives: 1) to assess the methodology of previously published economic models of LTBI screening and to develop an analytical framework, 2) to understand the experiences of asylum seekers with HE, 3) to quantify health-related quality of life (HRQoL) of LTBI patients and to explore the factors influencing it, 4) to quantify the HRQoL of TB patients, and 5) to assess the cost effectiveness of LTBI screening through an economic model.

Methods: A qualitative study was designed to explore the experiences of asylum seekers with HE; semi-structured interviews were conducted based on an interview guide. For the HRQoL studies, a HRQoL instrument, EQ-5D, and a mental health screening instrument, RHS-15, were used. For the LTBI patients, a mixed-method design was used, in which a crosssectional survey using the EQ-5D and RHS-15 instruments was combined with qualitative interviews of a subgroup. For the TB patients, a longitudinal study design was used in which a cohort filled the EQ-5D instrument at the beginning and the end of treatment. A literature review was performed to assess the methodology of published economic modelling studies of LTBI screening. Through this review a framework was developed guiding the development of an economic model (a Markov model) to assess the cost effectiveness of the current LTBI screening in Stockholm compared to a hypothetical scenario of no screening. The analysis adopted the societal perspective, and results were presented in term of incremental costeffectiveness ratios (ICERs); taking 500 000 SEK/QALY as a cost-effectiveness threshold.

Results: The HE was perceived as available by asylum seekers, with no serious physical or financial accessibility problems. They felt respected and trusted by the healthcare workers. However, information about the Swedish healthcare system was perceived to be incomplete and the HE was seen as non-responsive to their individual needs with main focus on infectious diseases. Among LTBI patients, 38% screened positive for mental health concerns using RHS-15, and 28% scored problems on mental health dimension of EQ-5D. These patients expressed fear of being contagious to others, an ambiguous threat of a vague diagnosis and future uncertainties about developing TB disease. However, LTBI patients had no overall HRQoL decrement. TB patients had a HRQoL utility score of 0,72 at the beginning of treatment, which improved significantly by the end of the treatment to 0,84. The cost effectiveness results showed that ICER is the lowest among the age group 13 to 19 at 303 881 SEK/QALY, which was the only ICER below the 500 000 SEK/QALY threshold.

Discussion: Asylum seekers had a generally positive attitude towards HE, including TB and LTBI screening, but also emphasized the need to broaden the focus on all health needs rather than solely focusing on infectious diseases. LTBI patients might have a compromised mental health partly linked to fear of TB disease. Therefore, it can be beneficial to address these concerns as part of LTBI management. TB patients had a compromised HRQoL and a decrement of 0,28 for TB patients is recommended to be used in economic evaluations. LTBI screening among asylum seekers in Stockholm is cost effective in the age group 13 to 19 while it is moderately cost-effective in the age groups 0 to 12 and 20 to 34 years. The latter is mainly due to the restrictive practices of offering treatment for persons over the age of 20 years.

Conclusions: Health examination is an acceptable, accessible health service. However, its quality can be improved by broadening the focus beyond infectious disease control. An LTBI diagnosis can be misunderstood as active TB and linked to stigma. The cost-effectiveness analysis showed that screening is cost effective only when preventive treatment is offered. Therefore, due to ethical and economic reasons, LTBI screening should only be performed for asylum seekers who are potentially eligible for LTBI treatment.