Screening for latent infection with Mycobacterium tuberculosis: a plea for targeted testing in low endemic regions

Abstract

Evaluation of: Mancuso JD, Mazurek GH, Tribble D et al. Discordance among commercially available diagnostics for latent tuberculosis infection. Am. J. Respir. Crit. Care Med. 185(4), 427–434 (2012).

The higher specificity proposed for IFN-γ-release assays (IGRAs) compared with tuberculin skin testing (TST) may indicate superiority in identifying patients at risk for progression towards active tuberculosis. Unfortunately, available assays may frequently show discordant results. To aid in interpreting discordant results, the article under evaluation has comparatively analyzed results of the TST and two commercially available IGRAs in a low-risk population for tuberculosis. TST-positive/IGRA-negative results were strongly associated with bacillus Calmette–Guérin vaccination or nontuberculous mycobacteria sensitization, whereas the etiology of TST-negative/IGRA-positive results or discrepancies among IGRAs remain unresolved. As the three tests identified different individuals in the majority of positive cases, this indicates that most positive results obtained in the absence of additional risk factors are falsely positive. By contrast, increasing concordance of positive results was associated with tuberculosis risk factors. This has direct implications for screening practices in low prevalence regions where a targeted screening approach may reduce both unnecessary testing and treatment.

Keywords::

• accuracy
• battey skin test
• discordance
• IGRA
• latent tuberculosis infection
• military recruits
• NTM
• QuantiFERON^®-TB gold in-tube test
• targeted testing
• T-SPOT^®.TB test
• TST

Financial & competing interests disclosure

D Goletti has received a grant from Cellestis to attend a scientific meeting in Croatia in 2009, and a partial travel reimbursement from A.D.A. to attend the ATS meeting in Canada in 2008. INMI, where D Goletti works, has received a grant from Oxford Immunotec as part of the salary for a laboratory technician in 2007. D Goletti has received a European patent on T-cell assay based on selected RD1 peptides for the diagnosis of the different stages of tuberculosis (number 1723426). M Sester has received a patent entitled 'in vitro process for the quick determination of a patient´s status relating to infection with Mycobacterium tuberculosis' (international patent number WO2011113953/A1). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.