EVALUATION AND OUTCOME OF PATIENTS WITH CHRONIC NONPRODUCTIVE COUGH USING A COMPREHENSIVE DIAGNOSTIC PROTOCOL

Background-Asthma, post-nasal drip syndrome (PNDS), and gastrooesophag eal reflux (GOR) account for many cases of chronic non-productive coug h (CNPC). Each may simultaneously contribute to cough even when clinic ally silent, and failure to recognise their contribution may lead to u nsuccessful treatment. Methods-Patients (all lifetime nonsmokers with normal chest radiographs and spirometric measurements) referred with C NPC persisting for more than three weeks as their sole respiratory sym ptom underwent histamine challenge, home peak flow measurements, ear, nose and throat (ENT) examination, sinus CT scanning, and 24 hour oeso phageal pH monitoring. Treatment was prescribed on the basis of diagno ses informed by investigation results. Results-Forty three patients (2 9 women) of mean age 47.5 years (range 18-77) and mean cough duration 67 months (range 2-240) were evaluated. On the basis of a successful r esponse to treatment, a cause for the cough was identified in 35 patie nts (82%) as follows: cough variant asthma (CVA) (10 cases), PNDS (9 c ases), GOR (8 cases), and dual aetiologies (8 cases). Histamine challe nge correctly predicted CVA in 15 of 17 (88%) positive tests. ENT exam ination and sinus CT scans each had low positive predictive values for PNDS (10 of 16 (63%) and 12 of 18 (67%) positive cases, respectively) , suggesting that upper airways disease frequently co-exists but does not always contribute to cough. When negative, histamine challenge and 24 hour oesophageal pH monitoring effectively ruled out CVA and GOR, respectively, as a cause for cough. Conclusion-This comprehensive appr oach aids the accurate direction of treatment and, while CVA, PNDS and GOR remain the most important causes of CNPC to consider, a group wit h no identifiable aetiology remains.