A cheaper, faster way to resolve chronic cough
“Presumed diagnosis” strategy offers early treatment, a cost savings, and >90% treatment response.
Another 141 patients (37%) diagnosed with asthma syndrome (with or without postnasal drip syndrome) reported cough resolution following successful treatment between 7 and 12 days.
Another 29 patients (8%) with re-flux syndrome were successfully treated between 14 and 26 days.
Treatment of chronic cough by the algorithm
After application of the therapeutic algorithm, the chronic cough of 346 patients (92%) resolved. Thirty-two patients (8.5%) underwent other diagnostic investigations.
Final diagnoses after further diagnostic testing
Ten patients reported that they stopped coughing spontaneously while awaiting additional diagnostic investigations. Seven patients had mycobacterial infections confirmed by acid fast bacilli smears or culture of sputum or bronchoscopic washings. Six patients had localized or diffuse bronchiectasis confirmed by high-resolution CT, the results of which were used retrospectively to reassess normal or equivocal findings in the initial diagnostic investigations. Finally, the coughs of 12 patients were judged to be idiopathic or psychogenic.
Discussion
Cough is a symptom not easily assessed objectively. Previous studies measured severity of cough with daily diaries and visual analog scales, which are subjective measurement tools. We, too, used the visual analog scale to measure cough severity and treatment response. We did not pursue a definitive diagnosis of the cause of chronic cough. Rather, our algorithmic approach made presumptive diagnoses that were confirmed or refuted by patients’ successive reports of cough severity in response to treatment.
The logic behind our algorithm
Because studies in Korea have shown that postnasal drip is the most frequent cause of chronic cough, we chose rhinoscopy as the first diagnostic investigation. The second and third steps of our approach investigated asthma syndrome and reflux syndrome, respectively.
We did not take into account whether patients smoked cigarettes. Some investigators rightly point out that smoking might contribute to chronic cough. However, we have not met many smokers willing to quit because of a cough, and our algorithm is designed for practical clinical use. In contrast, patients with chronic cough secondary to ACE inhibitor therapy have readily accepted trials of different antihypertensive medications.
Our assumptions proved true
Patients with any abnormality of the nasal mucosa were treated for postnasal drip syndrome. Though the proportion of abnormal mucosal findings was greater than that reported in previous investigations of the same ethnic subjects, the eventual treatment response showed that the presumptive diagnosis of postnasal drip was equivalent to that in other studies.10,11
Postnasal drip syndrome did indeed turn out to be the most common presumptive cause of cough in our study. However, roughly one third of these patients proved to have an additional presumptive disorder. Previous investigations have also reported dual or multiple pathologies in patients with a chronic cough.11,12
If treatment succeeded at any step in our algorithm, we asked patients to stop taking medication—with the exception of those who had positive results on methacholine bronchial provocation test. Asthma is a chronic inflammatory disorder that needs persistent therapy to prevent exacerbations and declining lung function.13,14 Challenge studies with methacholine or histamine are sensitive tests and provide high negative predictive values for the diagnosis of asthma and cough variant asthma.15,16
What have other studies shown?
The natural course of chronic cough is still in question, primarily because of the heterogeneity of its etiology. The natural course of many common diseases has been investigated, of course, but few studies have focused on duration of symptoms such as cough. Park et al17 investigated the natural course of eosinophilic bronchitis, a common underlying disorder in chronic cough. In a 48-month follow-up of 36 patients diagnosed with eosinophilic bronchitis, 14% experienced recurrence after treatment. And patients with a higher percentage of eosinophils in the sputum had a risk for developing airway hyperresponsiveness.
Ours et al9 reported that, for patients without asthma or postnasal drip, an empiric 2-week trial of high-dose proton pump inhibitors was more reliable and cost effective for chronic cough than was treatment after esophageal manometry or 24 hours dual probe pH monitoring. Besides the expense of manometry and pH monitoring, both procedures are invasive and unavailable in many localities such as ours. Our algorithm supposes, for one thing, minimum availability of medical equipment in many locales.
The algorithm makes sense
Our approach decreased medical expenses and therapeutic response periods. Cough resolved for more than 90% of our patients. This success rate was equivalent to that reported by previous studies, most of which revealed no definitive diagnosis during the therapeutic response period.2-4,18 Half of all patients in our study experienced cough resolution within 5 days, and more than 80% did so within 12 days.
