Smelling the diagnosis A review on the use of scent in diagnosing disease

摘要

For centuries, our sense of smell has been used as a diagnostic tool in the practice of medicine, be it for recognising gas gangrene on the battle field or diabetic ketoacidosis in the emergency room. In recent decades, many scent detection studies have been performed with human, animal and electronic noses. The ability of humans to diagnose disease by smelling has only rarely been the subject of quantitative studies. Scent detection by animals, on the other hand, has been addressed in several diagnostic studies, which all suggest similar or even superior accuracy compared with standard diagnostic methods. Examples include, amongst many others, the use of dogs for the detection of lung cancer in breath samples, or rats for Mycobacterium tuberculosis detection in sputum. Studies using different types of electronic noses in conditions such as pulmonary disease and cancer have also shown promising results with high overall sensitivity and specificity. However, results of different types of noses are not easily generalisable and independent confirmation studies are generally lacking, which should be a focus for future research. In conclusion, scent detection by animals and electronic noses holds promise for the future and should receive higher priority in terms of research effort and funding. diagnostic tool in the practice of medicine. Well-known examples include fetor hepaticus surrounding patients with liver failure, and the fruity smell of ketones in exhaled breath of patients with diabetic ketoacidosis. The sense of smell depends on the ability of specialised sensory cells of the nose to perceive volatile compounds. Diseases such as infections and malignancies can be associated with changes in host metabolism, accompanied by production of different metabolic compounds, and thus a different odour. In the late 1980s, a dog handler became increasingly suspicious of a mole after her dog constantly kept sniffing at the lesion on her leg and eventually even tried to bite it off.2 The consulted dermatologist subsequently diagnosed a melanoma. Since then, several studies have addressed animal scent detection as a diagnostic technique. Attempts to mimic the biological olfactory system resulted in several types of electronic noses (Enoses)3 which are also increasingly used in the medical field. In this clinical review, we discuss different types and applications of scent detection and their potential as diagnostic tools in modern medicine.