Screening of immigrants in the UK for imported latent tuberculosis: a multicentre cohort study and cost-effectiveness analysis

Abstract

SummaryBackgroundContinuing rises in tuberculosis notifications in the UK are attributable to cases in foreign-born immigrants. National guidance for immigrant screening is hampered by a lack of data about the prevalence of, and risk factors for, latent tuberculosis infection in immigrants. We aimed to determine the prevalence of latent infection in immigrants to the UK to define which groups should be screened and to quantify cost-effectiveness.MethodsIn our multicentre cohort study and cost-effectiveness analysis we analysed demographic and test results from three centres in the UK (from 2008 to 2010) that used interferon-γ release-assay (IGRA) to screen immigrants aged 35 years or younger for latent tuberculosis infection. We assessed factors associated with latent infection by use of logistic regression and calculated the yields and cost-effectiveness of screening at different levels of tuberculosis incidence in immigrants' countries of origin with a decision analysis model.FindingsResults for IGRA-based screening were positive in 245 of 1229 immigrants (20%), negative in 982 (80%), and indeterminate in two (0·2%). Positive results were independently associated with increases in tuberculosis incidence in immigrants' countries of origin (p=0·0006), male sex (p=0·046), and age (p<0·0001). National policy thus far would fail to detect 71% of individuals with latent infection. The two most cost-effective strategies were to screen individuals from countries with a tuberculosis incidence of more than 250 cases per 100 000 (incremental cost-effectiveness ratio [ICER] was £17 956 [£1=US$1·60] per prevented case of tuberculosis) and at more than 150 cases per 100 000 (including immigrants from the Indian subcontinent), which identified 92% of infected immigrants and prevented an additional 29 cases at an ICER of £20 819 per additional case averted.InterpretationScreening for latent infection can be implemented cost-effectively at a level of incidence that identifies most immigrants with latent tuberculosis, thereby preventing substantial numbers of future cases of active tuberculosis.FundingMedical Research Council and Wellcome Trust.

Latent tuberculous screening of recent migrants attending language classes: a cohort study and cost analysis

“…This option identified 80.9% of IGRA positive results with an average cost of £17,845.61 and an incremental cost of £25,521 per case avoided. This is consistent with the findings of Pareek et al 1 who report that that screening migrants from countries with a TB incidence of 150 per 100,000 was similarly cost effective and captures the majority of LTBI cases.…”

“…Latent TB infection (LTBI) screening of new immigrants from countries with a high incidence of TB is an effective and cost effective way to identify eligible individuals for preventive treatment and thereby prevent subsequent cases of active disease [1][2][3] . The UK National Institute for Health and Care Excellence (NICE) and the World Health Organization (WHO) both recommend a targeted screening approach to individuals at highest risk of reactivation 4,5 .…”

Immigrant screening for TB: a missed opportunity to improve TB control in the United Kingdom

“…5 The conclusions of this analysis were that screening as per the 2006 NICE guidelines would miss 70% of imported LTBI and therefore immigrant screening would be most costeffectively implemented by revising the screening threshold downwards to an intermediate incidence threshold of 150-250/100000 which would identify 90% of immigrants with LTBI, thereby preventing substantial numbers of future active TB cases. 5 In 2011 NICE published revised guidelines that actually dropped the threshold further to 40/100 000; however, it remains unclear whether this guidance will be acted upon. In view of limited service capacity and the huge logistical and cost implications of screening all new entrants from countries with TB incidence .40/100 000, TB services may instead use a higher threshold which would reduce the number of individuals eligible to be screened.…”

Interferon-γ release assays for the diagnosis of latentMycobacterium tuberculosisinfection

“…Although the potential cost-effectiveness of an IGRA for the investigation of LTBI has recently been demonstrated in immigrant screening in the UK [10], information on the predictive values of IGRAs for the development of tuberculosis still relies on a small number of at-risk individuals who actually developed tuberculosis. Clearly, more information is needed before general recommendations that IGRAs should replace the TST can be made.…”