McGarvey et al 1 suggest that full investigation of patients with persistent cough improves treatment.

I reviewed 100 such patients seen consecutively. All had normal chest radiographs, two were current smokers, and their mean cough duration was 18.8 months (range one month to 20 years). Initial treatment was given on the basis of history and routine clinical examination with investigations reserved for patients not responding after one month. Thirty four patients failed to return after their initial appointment. Twenty were contacted and all reported complete resolution of their symptoms. Clinical diagnoses in the 14 others were similar and they probably defaulted because of improvement, but have been excluded from analysis. Investigations performed included radiology of the sinuses in 8%, bronchial provocation testing …