Cysteine challenge test as a novel diagnostic tool to distinguish oral halitosis

The cysteine challenge test is often used to check the H₂ S production capacity of the mouth. Patients with oral halitosis group (n = 305) or non-oral halitosis group (n = 191) and healthy individuals (control group, n = 102) were compared with each other to identify any possible relationship between initial and cysteine-induced oral H₂ S concentrations.

The medical records of 598 participants were reviewed retrospectively. Oral H₂ S concentrations before (pre-CR) and after cysteine rinse (post-CR) with 5 mL of 20 mmol L-cysteine solution for 30 s were compared.

Pre-CR H₂ S concentrations were >0.8 ppm in 75.1% of oral group patients but less than <0.8 ppm in 87.3% of the non-oral group and 86.9% of controls. After cysteine rinse, oral H₂ S concentrations exceeded 12 ppm in 72% of the oral halitosis patients but were lower in 88% of non-oral group and 99% of controls. Whilst post-CR/pre-CR ratio was >12 in 74.5% of the oral group, it was <12 in 81.7% of the non-oral group and 83.4% of controls.

Cysteine challenge test can be used as a diagnostic tool to identify an individual's tendency to produce oral malodor, not only to quantify momentary halitosis level.