Volume 199 - Issue 10
Immigration screening for latent tuberculosis infection
Authors: David W J Griffin and Mark D Kelly
Med J Aust 2013; 199 (10): 654. || doi: 10.5694/mja13.10953
Published online: 18 November 2013
Published online: 18 November 2013
Unresolved issues regarding screening for latent tuberculosis infection and management make it difficult to strike a balance between costs (including risks) and benefits of screening.
To the Editor: The recent article by Denholm brings timely attention to the importance of screening for latent tuberculosis infection (LTBI) in at-risk populations.1 Currently, screening for LTBI is targeted to patients who are thought to be at highest risk of reactivation, including patients infected with HIV and those receiving immunomodulator therapies. Given that the greatest risk factor for active TB in Australia is immigration from a region where TB is endemic, it seems reasonable to screen immigrants from endemic areas.
The premise of screening is to identify patients who will benefit from isoniazid prophylactic therapy (IPT). However, a number of unresolved issues regarding LTBI screening and management make widespread implementation problematic. First, the lifetime risk of LTBI reactivation is inherently low (2%–7%),2 meaning that LTBI is innocuous for most patients. Second, current tests are imperfect, with poor positive predictive value for reactivation in low-incidence settings; not all patients with positive test results are at equal risk of reactivation.3 Moreover, test sensitivity may be adversely affected by factors that increase reactivation risk (eg, immunosuppression). Third, the likelihood that the patient will complete 6–9 months of IPT is limited by drug toxicities.4 Retrospective data collected from the charts of 57 patients who attended the Brisbane Sexual Health and HIV Service during a 9-year period, from 2002 to 2011, show that IPT was discontinued prematurely for 18 patients, after a median duration of 4 months (interquartile range, 1.25–5 months) (own unpublished data). The reasons for discontinuing IPT are shown in the Box. Severe adverse reactions were uncommon in this group of patients.
Since screening confers an obligation to treat patients with positive test results, a screening program should identify patients who are at the highest risk of reactivation and most likely to complete IPT, and thus most likely to benefit from treatment.
Competing interests
No relevant disclosures
References
- Denholm JT. Immigration screening for latent tuberculosis infection. Med J Aust 2013; 198: 524.
- Marks GB, Bai J, Simpson SE, et. al. Incidence of tuberculosis among a cohort of tuberculinpositive refugees in Australia. Reappraising the estimates of risk. Am J Respir Crit Care Med 2000; 162: 1851-1854.
- Diel R, Loddenkemper R, Nienhaus A. Predictive value of interferon-gamma release assays and tuberculin skin testing for predicting progression from latent TB infection to disease state: a metaanalysis. Chest 2012; 142: 63-75.
- LoBue PA, Moser KS. Use of isoniazid for latent tuberculosis infection in a public health clinic. Am J Respir Crit Care Med 2003; 168: 443.