Assessment of potential causes of falsely positive Mycobacterium tuberculosis breath test.

A suite of volatiles have previously been identified as specific markers of Mycobacterium tuberculosis metabolism in vitro. These markers - methyl phenylacetate, methyl p-anisate, methyl nicotinate, o-phenylanisole with the addition of methyl salicylate, may also be derived from other sources and confound development of a breath test for tuberculosis. To identify potential sources of these potential biomarkers food products, cosmetics, TB medication, environmental air and cigarette smoke were analysed for these markers using solid phase microextraction coupled with Gas Chromatography/Mass Spectrometry. Breath from healthy subjects, including smokers was also tested. Methyl salicylate was commonly detected, making this unsuitable as a specific marker for M. tuberculosis. Methyl nicotinate was detected repeatedly in cigarettes. Methyl phenylacetate was detected in 1.7% of healthy subjects and o-phenylanisole in just 1% of healthy breath indicating these may be more suitable for inclusion in the tuberculosis breath test due to their low "background" level. These results justify further clinical studies to further explore these markers as specific indicators of M. tuberculosis infection.