We would like to draw your readers’ attention to the fact that the 11th revision of the International Classification of Diseases (ICD-11) proposed by the WHO is currently out for consultation. In common with previous versions of the ICD, this revised version does not contain a code for latent tuberculosis infection (LTBI). This contrasts with the inclusion of an extensive and complex coding system for various manifestations of active tuberculosis (TB) disease, including rather obscure entities such as ‘involvement of eyelid in TB’.

The true burden of LTBI is largely unknown, although WHO estimates suggest that a third of the global population has LTBI.1 However, with a few exceptions, reporting of TB worldwide only extends to cases with active TB, and consequently the true prevalence of LTBI in both adults and in children remains uncertain.2 Since cases with LTBI are ultimately the ‘reservoir’ perpetuating the ongoing TB pandemic, diagnosis and treatment of LTBI to prevent progression to active TB has been declared a key component in the WHO Global Plan to Stop TB.3

We believe that the inclusion of a separate code for LTBI is of critical importance to (i) define the burden of LTBI more accurately, (ii) allow identification of LTBI cases from existing clinical databases to facilitate reimbursement of care and medication provided, and planning of clinical services, and (iii) enable epidemiological and laboratory-based TB research focusing on improving our understanding of LTBI.

The Paediatric Tuberculosis Network European Trialsgroup, comprising clinicians, epidemiologists and researchers from 23 European countries, has recently submitted a proposal to the WHO suggesting the addition of a separate ICD code for LTBI. We proposed that LTBI should be defined as ‘a positive immunological test result (either tuberculin skin test or interferon-gamma release assay) in the absence of active TB’. We are aware that this definition has limitations, but in the absence of a gold standard for the diagnosis of LTBI embarking on complex definitions is unlikely to be useful in this context.4 ,5 Furthermore, we believe that such a deliberately broad definition is needed to allow clinicians involved in case management to make the decision on an individual patient basis as to whether LTBI is likely, by taking into account several factors that are difficult to quantify, including the patient's cumulative risk of exposure to Mycobacterium tuberculosis.

We strongly encourage our colleagues worldwide who are involved in the care of TB patients or TB research to register as individual or group stakeholders via the ICD-11 Beta website (http://apps.who.int/classifications/icd11/browse/f/en), and join us in supporting the case for a much-needed ICD code for LTBI. Together we can help shape ICD-11 and make an important change happen that has been long overdue.