OBJECTIVES: Acetaldehyde, the first metabolite of ethanol, is a definite carcinogen for the esophagus, head, and neck; and aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that catalyzes the metabolism of acetaldehyde. The ALDH2 genotype exists as ALDH21/1 (active ALDH2), ALDH21/2 (heterozygous inactive ALDH2), and ALDH22/2 (homozygous inactive ALDH2). Many epidemiological studies have reported that ALDH22 carriers are at high risk for esophageal or head and neck squamous cell carcinomas by habitual drinking. Therefore, identification of ALDH22 carriers would be helpful for the prevention of those cancers, but there have been no methods suitable for mass screening to identify these individuals. METHODS: One hundred and eleven healthy volunteers (ALDH21/1 carriers: 53; ALDH21/2 carriers: 48; and ALDH22/2 carriers: 10) were recruited. Breath samples were collected after drinking 100 ml of 0.5% ethanol using specially designed gas bags, and breath ethanol and acetaldehyde levels were measured by semiconductor gas chromatography. RESULTS: The median (range) breath acetaldehyde levels at 1 min after alcohol ingestion were 96.1 (18.1 399.0) parts per billion (p.p.b.) for the ALDH21/1 genotype, 333.5 (78.4 1218.4) p.p.b. for the ALDH21/2 genotype, and 537.1 (213.2 1353.8) p.p.b. for the ALDH22/2 genotype. The breath acetaldehyde levels in ALDH22 carriers were significantly higher than for the ALDH21/1 genotype. Notably, the ratio of breath acetaldehyde level-To-breath ethanol level could identify carriers of the ALDH22 allele very accurately (whole accuracy; 96.4%). CONCLUSIONS: Our novel breath test is a useful tool for identifying ALDH22 carriers, who are at high risk for esophageal and head and neck cancers.
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Aoyama, I., Ohashi, S., Amanuma, Y., Hirohashi, K., Mizumoto, A., Funakoshi, M., … Muto, M. (2017). Establishment of a quick and highly accurate breath test for aldh2 genotyping. Clinical and Translational Gastroenterology, 8(6). https://doi.org/10.1038/CTG.2017.30