Chronic cough: Pepper to refine the diagnosis

Make a patient inhale capsaicin - a compound extracted from chili - to measure concentrations at which a cough is triggered, is the way advocated by British specialists to distinguish different types of cough.

According to findings the capsaicin test could be a reliable and reproducible aid to help doctors make a diagnosis when they are faced with a chronic cough.

Coughing is a subjective symptom that is difficult to define in consultation. Hence the value of a test that would allow to differentiate the types of coughs, particularly those with psychogenic origins from the true cause cough, and to quantify this symptom.

The test could also have an interest after the initial diagnosis, to monitor later changes. Another plus: this test is not expensive. The pepper extract, prepared in a lab, just has to be formulated for administration to patients in an aerosol dispenser.

Researchers have evaluated this test on 7 asthmatics, 10 patients with pulmonary fibrosis, 8 with Sjögren's syndrome (a chronic inflammatory disease characterized by dry eyes and mouth) and 51 control patients.

Patients initially received placebo (saline), then increasing doses of capsaicin. The criterion was the concentration of capsaicin needed to induce a fit of coughing after 5 to 15 seconds after nebulization.

Overall, patients with bronchial hypersecretion, such as those suffering from chronic obstructive pulmonary disease, coughed at the same concentration level as the healthy subjects.

Instead, people with dry cough, such as asthma, Sjögren's syndrome or induced reflux esophagitis, coughed earlier, at lower concentrations. As for psychogenic cough, it was triggered by placebo.

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