Unmet need for biomarkers in chronic cough: a review of current challenges and future directions.

The diagnosis, investigation and management of chronic cough remains a challenge for patients and physicians. Patients with chronic cough can spend many years being investigated for possible underlying conditions and have numerous therapies before a diagnosis of refractory and unexplained chronic cough (RCC/UCC) is made. Recognising that RCC/UCC is a distinct disease with underlying neuro-pathological features which commonly present with clinical features of cough hypersensitivity syndrome would be key to improved management of these patients. Biomarkers are used across various specialities to aid diagnosis, direct treatment and monitor treatment response; however, at present, no such biomarkers exist for RCC/UCC. Biomarkers are needed for RCC/UCC that could potentially be used to identify and predict treatment response. Advances in the mechanisms and therapies for refractory chronic cough targeting the peripheral nerves expressing the P2X3 receptor, and opioid pathways in the central nervous system have provided hope for developing novel biomarkers. However, the development of biomarkers remains a challenging process and there is a need for ongoing research to address the lack of evidence in this area.