Advances in breath and saliva analysis

Breath and saliva share a series of features that allow them to provide complementary and clinically valuable information. Their components originate from normal or abnormal physiology, ingestion and metabolization of food and beverage, exposure to pollutants and bacterial activity. The rapid equilibrium with blood provides these biological fluids with a high potential for the diagnosis of diseases as well as the monitoring of disease progression and therapy. The combination of non-invasive sampling and the fact that their composition mirrors almost in real time processes occurring inside the body makes breath and saliva analysis suitable for monitoring drug therapies, for example to detect potential adverse effects or to provide insights on the pharmacokinetics or on the mechanism of action. From the analytical point of view, breath and saliva offer the advantage of reduced background levels (compared to blood) of chemical interferents, but this is usually paid with lower concentration levels of the target compounds. Sampling procedures of both fluids are critical, as they may have remarkable effects on the composition of the collected specimens. Storage of samples is also critical in the case of breath, whereas saliva does not generally require particular attention. In this work, the use of breath and saliva analysis in the pharmacological field is reviewed and practical applications are shown. After a brief introduction concerning the basics of breath and saliva analysis, more attention is devoted to the sampling procedures and their effects on sample composition. A series of illustrative applications in the pharmacological field concludes the work showing the present use of these techniques and trends for the future.