Evaluation and outcome of patients with chronic non-productive cough using a comprehensive diagnostic protocol

Serum and sputum neurotrophin levels in chronic persistent cough

BACKGROUND

Neurotrophins (NTs) are a family of growth factors, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin3 (NT-3) that are involved in inflammation. Serum and induced sputum NT levels are increased in asthma and in cough because of idiopathic pulmonary fibrosis, respectively. Neurogenic inflammation is implicated in the pathogenesis of chronic cough in individuals with normal chest radiography, but the role of NTs in this condition is unknown.

OBJECTIVE

To assess if NT levels are elevated in the serum and airways in subjects with chronic persistent cough.

METHODS

Eighty-one subjects with chronic cough persistent for over 1 year; with normal chest radiography and spirometry were included. Thirty healthy subjects were controls. Serum NGF, BDNF and NT-3 were measured by enzyme immunoassay. In a subset, NGF was measured in induced sputum. Sputum cell counts and allergen-specific serum IgE were measured and all patients received specific sequential treatment trials to achieve a final diagnosis for the cough.

RESULTS

There was no significant difference either in the levels of serum or sputum NTs in chronic cough subjects compared with controls or between the most common causes of cough: post-nasal drip syndrome, gastro-oesophageal reflux disease, asthma and bronchiectasis. The median (inter-quartile range) for sputum NGF (pg/mL) was 516 (296-772) in healthy controls and 580 (312-880) in subjects with chronic cough (P=0.284). There was no correlation between NT levels and sputum cell counts. Sputum NGF levels correlated with duration of cough (r=0.34, P=0.002).

CONCLUSION

NTs are not elevated in induced sputum or serum of subjects with chronic persistent cough. This implies that NTs do not have a central role in perpetuating airway inflammation in chronic persistent cough.

Chronic Cough Due to Gastroesophageal Reflux Disease

OBJECTIVES

To critically review and summarize the literature on cough and gastroesophageal reflux disease (GERD), and to make evidence-based recommendations regarding the diagnosis and treatment of chronic cough due to GERD.

DESIGN/METHODOLOGY

Ovid MEDLINE literature review (through March 2004) for all studies published in the English language and selected articles published in other languages such as French since 1963 using the medical subject heading terms "cough," "gastroesophageal reflux," and "gastroesophageal reflux disease."

RESULTS

GERD, singly or in combination with other conditions, is one of the most common causes of chronic cough. In patients with normal chest radiographic findings, GERD most likely causes cough by stimulation of an esophageal-bronchial reflex. When GERD causes cough, there may be no GI symptoms up to 75% of the time. While 24-h esophageal pH monitoring is the most sensitive and specific test in linking GERD and cough in a cause-effect relationship, it has its limitations. In addition, there is no general agreement on how to best interpret the test, and it cannot detect non-acid reflux events. Therefore, when patients fit the clinical profile that has a high likelihood of predicting that GERD is the cause of cough, antireflux medical therapy should be empirically instituted. While some patients improve with minimal medical therapy, others require more intensive regimens. When empiric treatment fails, it cannot be assumed that GERD has been ruled out as a cause of chronic cough. Rather, an objective investigation for GERD is then recommended because the empiric therapy may not have been intensive enough or medical therapy may have failed. Surgery may be efficacious when intensive medical therapy has failed in selected patients who have undergone an extensive objective GERD evaluation.

CONCLUSIONS

Accurately diagnosing and successfully treating chronic cough due to GERD can be a major challenge.

Airway inflammation and cough sensitivity in cough-variant asthma

BACKGROUND

Mechanisms underlying cough and bronchoconstriction in patients with cough-variant asthma (CVA) are not well established. Differences in location or degree of activation of eosinophils and allergic cytokines have been suggested as the likely causes. To address this issue, we have carried out a comparative study of airway inflammatory markers between patients with CVA and classic asthma (CA). The relationship between these markers with airway hyperresponsiveness (AHR) and cough sensitivity has also been studied.

METHODS

Twenty-seven non-smokers and steroid-naive patients with CVA (12) and CA (15) were examined. Capsaicin challenge, histamine bronchoprovocation test, nitric oxide levels in exhaled air and sputum induction were performed in all of them. Differential cell sputum recount and supernatant concentrations of eosinophil granule-derived cationic proteins (ECP), interleukin (IL)5, IL8 and tumour necrosis factor (TNF)-alpha were also measured.

RESULTS

There were no significant differences in either the inflammatory pattern of soluble markers or differential cell counts between CA and CVA. Histamine PC20 was correlated with IL-5 in CVA, whereas it was associated with sputum eosinophilia in CA. Cough sensitivity (log C5) and histamine PC20 were inversely related in CA.

CONCLUSIONS

Although the pattern of inflammatory sputum markers in patients with asthma and cough-variant asthma is similar, its relation with bronchial hyperreactivity and cough sensitivity is different in each group.

Prevalence and clinical features of cough variant asthma in a general internal medicine outpatient clinic in Japan

OBJECTIVE

The aims of the present study were to examine the prevalence and clinical features of cough variant asthma (CVA) among patients with chronic and persistent cough at an outpatient clinic in Japan, and the efficacy of treatment with an inhaled corticosteroid.

METHODOLOGY

This prospective study was conducted at a general internal medicine outpatient clinic in Japan over a 12-month period. CVA was diagnosed as chronic cough without wheezing or any apparent cause, that had persisted for more than 8 weeks, with a normal CXR and spirometry but with bronchial hyperresponsiveness to methacholine, and relief of cough after bronchodilator treatment. We also examined the effects of inhaled beclomethasone propionate on symptoms and differences in PEF between early morning and evening.

RESULTS

Of 55 patients suffering from chronic cough, 23 satisfied the criteria for CVA. Their cough occurred more frequently at night and early in the morning. Early morning PEF was significantly lower than evening PEF with a mean variability of 11.5 +/- 4.1%. Treatment with beclomethasone propionate improved coughing and significantly increased early morning PEF, reducing variability to less than 10%.

CONCLUSIONS

These findings suggest that CVA is most common among patients with chronic cough not due to any apparent cause. The efficacy of inhaled corticosteroid suggests that early intervention is effective in the treatment of CVA.

Idiopathic chronic cough: a real disease or a failure of diagnosis?

Despite extensive diagnostic evaluation and numerous treatment trials, a number of patients remain troubled by a chronic and uncontrollable cough. Eosinophilic bronchitis, atopic cough and non-acid reflux have been recently added to the diagnostic spectrum for chronic cough. In some cases, failure to consider these conditions may explain treatment failure. However, a subset of patients with persisting symptoms may be regarded as having an idiopathic cough. These individuals are most commonly female, of postmenopausal age and frequently report viral upper respiratory tract infections as an initiating event. This paper seeks to explore the validity of idiopathic cough as a distinct clinical entity.

Safety of capsaicin cough challenge testing

BACKGROUND

Capsaicin, the pungent extract of red peppers, has achieved widespread use in clinical research because it induces cough in a dose-dependent and reproducible manner. Although > 2 decades of experience has led investigators to consider capsaicin cough challenge testing a safe diagnostic modality, this issue has not been specifically addressed in the literature.

STUDY OBJECTIVES

To review the published experience with capsaicin inhalation challenge testing in terms of safety.

DESIGN

Literature review and personal communication with study authors.

SETTING

Academic medical center.

RESULTS

One hundred twenty-two published studies since 1984 described 4,833 subjects (4,374 adults, 459 children) undergoing capsaicin cough challenge, with no serious adverse events reported. Subjects included healthy volunteers as well as patients with asthma, COPD, pathologic cough, and other respiratory conditions. Minor complaints described in a small fraction of studies consisted mainly of transient throat irritation. Personal communication with the authors of > 90% of the studies confirmed an absence of any serious adverse events. Furthermore, these investigators have performed thousands of additional capsaicin challenge studies not reported in the literature, also without any associated serious adverse events.

CONCLUSIONS

A review of the 20-year clinical experience has failed to uncover a single serious adverse event associated with capsaicin cough challenge testing in humans. Given the need for better antitussive therapies, capsaicin represents a vital component of future scientific inquiry in the field of cough.

Change in bronchial responsiveness and cough reflex sensitivity in patients with cough variant asthma: effect of inhaled corticosteroids

BACKGROUND

Cough variant asthma (CVA) is a cause of chronic cough and a precursor of typical asthma. We retrospectively examined the longitudinal change in bronchial responsiveness and cough reflex sensitivity in CVA patients with respect to the effect of long-term inhaled corticosteroids (ICS).

METHODS

Provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (PC20-FEV1) and provocative concentration of capsaicin eliciting 5 or more coughs (C5) were measured before treatment and during a follow up period following relief of cough (median; 2.0 (range; 0.5 to 8.0) years after the initial visit) in a total of 20 patients with CVA (7 males and 13 females, mean +/- SD age of 49.9 +/- 12.9 years).

RESULTS

Three of 8 patients not taking long-term ICS developed typical asthma compared to none of 12 patients taking ICS (p = 0.0171). PC20-FEV1 significantly (p < 0.0001) increased from 1.80 (GSEM, 1.35) to 10.7 (GSEM, 1.63) mg/ml in patients taking ICS but did not change in patients not taking ICS [2.10 (GSEM, 1.47) compared to 2.13 (GSEM, 1.52) mg/ml]. Cough threshold did not change in patients whether taking or not taking ICS.

CONCLUSION

Long-term ICS reduces bronchial hyperresponsiveness in CVA as recognized in typical asthma. Cough reflex sensitivity is not involved in the mechanism of cough in CVA.

Characteristics of patients with chronic cough who developed classic asthma during the course of cough variant asthma: a longitudinal study

BACKGROUND

Some patients develop asthmatic symptoms such as wheezing and dyspnea during the course of cough variant asthma (CVA), which are considered precursors of classical asthma.

OBJECTIVES

To identify the characteristics of such patients, we investigated the nature of CVA patients with or without developing bronchial asthma in the longitudinal study.

METHODS

In 28 CVA patients whom we could observe over 5 years, duration of coughing, physical examination findings, pulmonary function and bronchial hyperresponsiveness to inhaled methacholine were retrospectively assessed.

RESULTS

Of these patients with CVA, 10 developed the asthmatic symptoms of wheezing and dyspnea (precursors of classical asthma) over 5 years. All these 10 patients showed marked bronchial hyperresponsiveness; however, there were no significant differences in the bronchial responsiveness to methacholine between patients with precursors of classical asthma and pure CVA patients who did not wheeze. The duration of coughing had a significant relationship with precursors of classical asthma. Seven patients with precursors of classical asthma developed wheezing in the first year and 1 patient each in the second, third and fourth year.

CONCLUSIONS

These findings of a 5-year observation suggest that longer duration of coughing may be an important factor that develops precursors of classical asthma in patients with CVA.

Evaluation and impact of chronic cough: comparison of specific vs generic quality-of-life questionnaires

BACKGROUND

Chronic cough is a common condition that has a significant impact on health-related quality of life (HRQoL).

OBJECTIVE

To investigate whether chronic cough is associated with adverse psychological and physical effects on quality of life (QoL) using different HRQoL questionnaires.

METHODS

Forty patients were recruited for the study. The diagnostic workup was mainly based on the pathogenic triad in chronic cough: postnasal drip syndrome, asthma, and gastroesophageal reflux disease. The HRQoL was evaluated with the cough-specific quality-of-life questionnaire (CQLQ), Leicester Cough Questionnaire (LCQ), Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and Hospital Anxiety and Depression Scale.

RESULTS

Symptom scores were significantly correlated with the CQLQ and LCQ (beta = .415 and beta = -.272, respectively) but not with the SF-36. A statistically significant difference was found in all questionnaires, except the physical component summary domain of the SF-36, after specific therapy. Correlation between the 2 specific HRQoL questionnaires was moderate to high when pretreatment and posttreatment scores were compared (r = -0.42 and r = -0.60). Concurrent validity of the LCQ was higher than the CQLQ when compared with the SF-36 domains. The effect size of each specific QoL questionnaire was 1 or higher after treatment, whereas it was much less in the SF-36. There was no change in depression with treatment despite anxiety. Posttreatment symptom scores were related with anxiety (r > 0.40)

CONCLUSIONS

Because HRQoL is important to patients, a cough-specific HRQoL instrument, either the CQLQ or LCQ, should be routinely used to optimally evaluate the impact of cough on patients and to evaluate the efficacy of cough-modifying agents.

Chronic idiopathic cough: a discrete clinical entity?

STUDY OBJECTIVES

Despite the success of specialist cough clinics, there is increasing recognition of a subgroup of chronic coughers in whom a diagnosis cannot be made even after thorough, systematic investigation. We call this condition chronic idiopathic cough (CIC). The aim of this study is to compare the clinical characteristics of CIC patients with those of coughers in whom a diagnosis has been established (non-CIC) to see if there is a recognizable clinical pattern that distinguishes CIC from non-CIC.

DESIGN

Retrospective analysis of the medical records of chronic cough patients.

SETTING

The Royal Brompton Hospital Chronic Cough Clinic, London.

PATIENTS

One hundred patients with chronic cough referred to the Royal Brompton Hospital Cough Clinic between October 2000 and February 2004.

RESULTS

Seventy-one percent of all patients were female. Median age was 57 years (range, 19 to 81 years), with a median duration of symptoms of 48 months (range, 2 to 384 months). The primary diagnoses were CIC (42%), postnasal drip syndromes (22%), gastroesophageal reflux disease (16%), asthma (7%), and others (13%). In CIC patients, the median age at referral, age at onset of cough, and proportion of females did not differ significantly from non-CIC patients. CIC patients had a longer median duration of cough (72 months vs 24 months, p = 0.002), were more likely to report an upper respiratory tract infection (URTI) as the initial trigger of their cough (48% vs 24%, p = 0.0014), and had a significantly lower cough threshold in response to capsaicin (log concentration of capsaicin required to induce five or more coughs, - 0.009 vs 0.592, p = 0.032) than non-CIC patients.

CONCLUSIONS

Patients with CIC commonly describe a URTI that initiates their cough, which then lasts for many years, and they demonstrate an exquisitely sensitive cough reflex. We believe that CIC may be a distinct clinical entity with an as-yet unidentified underlying pathology.

Noneosinophilic CD4 Lymphocytic Airway Inflammation in Menopausal Women With Chronic Dry Cough

BACKGROUND

Chronic dry cough without dyspnea and wheezing is a well-known condition that is considered to be clinically overrepresented in women. The etiology and morphology remain unknown in many cases despite thorough investigations.

DESIGN

To examine inflammatory cells and the lymphocyte profile in the lower airways and blood in women with chronic cough of unknown etiology.

SETTING

University hospital department of respiratory medicine.

PARTICIPANTS

Twenty-five otherwise healthy women with idiopathic cough and 11 age-matched healthy control women, all nonatopic nonsmokers.

MEASUREMENTS

In order to characterize the cough, a careful standardized interview of the patients was made. Lung functions were tested. Cells were collected by BAL and analyzed for differential cell counts separate in the bronchial (first) wash and in the pooled peripheral washes (BAL fluid). The lymphocyte profile in BAL fluid and blood was characterized by dual-color flow cytometry.

RESULTS

Eleven female patients formed a specific group with a history of a dry, nonproductive cough that always started in connection with an airway infection coinciding with menopause. Neither exercise, climate, nor seasonal change influenced the cough. BAL fluid contained an increased number of T (CD3+) lymphocytes: median. Seventy-three percent of T lymphocytes were T-helper lymphocytes (CD4+). A median of 57% of the BAL fluid T cells expressed HLA-DR activation marker compared with a median of 20% in the control subjects and in the other 14 included patients with chronic cough but with minor expectoration periodically (p < 0.001 and p < 0.0001, respectively). No differences between the groups were found in the blood.

CONCLUSIONS

HLA-DR-activated CD4+ lymphocytic airway inflammation with a low number of eosinophils was identified in a group of nonsmoking, nonatopic otherwise healthy women patients with dry cough of life-long character. The disease appeared exclusively in connection to menopause.

Acute and chronic cough

Individuals are generally content to self-medicate for acute cough. It is only when the cough becomes persistent that they seek medical assistance. It is not known why patients cough in association with an acute upper respiratory tract infection (URTI), although interest has focused on how viruses may influence airway sensory nerve function and contribute to heightened cough reflex sensitivity. Why some patients develop a persistent cough following a viral URTI is also unclear. Much more is known about the causes and aggravants of chronic cough although there is no broad agreement as to the best way to manage such patients. Asthma, upper gastrointestinal dysfunction and rhinitis are frequently associated with chronic cough, although the impact of cough in suppurative lung disease and interstitial lung fibrosis is rarely considered. The development of effective treatments for cough remains a challenge and will require co-operation between clinicians, scientists and the pharmaceutical industry.

Potential new cough therapies

Cough is among the most common complaints for which patients seek medical attention. Consequently, enormous expenditures are made worldwide on prescription and non-prescription cough remedies. Multiple prospective studies have shown that specific antitussive therapy aimed at the underlying aetiology of cough is highly successful. The greatest current need therefore is for more effective nonspecific antitussive therapy, whose purpose is to suppress the cough reflex and provide symptomatic relief regardless of the underlying mechanism. Such therapy is particularly required for prolonged cough following upper respiratory tract infection, cough whose underlying aetiology is not easily treated, and idiopathic cough. Many areas of inquiry are currently ongoing that may lead to the development of novel and effective antitussive drugs.

Post-nasal drip syndrome--a symptom to be sniffed at?

The syndrome or pseudo-syndrome of post-nasal drip (PNDS) represents a diagnostic label which is unhelpful in the understanding of chronic cough. There is no accepted definition of PNDS and no accepted method of measurement. The symptom of mucus dripping down the back of the throat occurs in normal subjects and is also reported by many patients in ENT clinics who do not have a cough. The lack of any clear pathological or biochemical tests makes the syndrome both a catch-all and a dustbin.

Rhinitis is an independent risk factor for developing cough apart from colds among adults

BACKGROUND

In cross-sectional clinical studies, rhinitis has been shown to be strongly associated with co-existing chronic cough. However, to date, this association has been poorly delineated from a prospective and epidemiological standpoint.

METHODS

We used data from the 'Pisa Prospective Study', a population-based longitudinal cohort study composed of a baseline and a follow-up survey taken approximately 5 years apart from each other. Information on cough, rhinitis, and other risk factors was collected by standardized questionnaire. Cough apart from colds was defined as either 'chronic' (most days for at least 3 months for at least two consecutive years) or 'occasional' (if the three above temporal conditions were not met). 'Any' cough was defined as the presence of either occasional or chronic cough.

RESULTS

Complete information was available for 1670 subjects who were > or =15 years old and had no positive history of cough apart from colds at the baseline survey. Among them, 299 (18%) had rhinitis at baseline. By the follow-up survey, 16% of the subjects with rhinitis had developed any cough apart from colds, as compared with only 10% of the subjects without rhinitis (OR 1.7, 95% CI 1.2-2.5, P < 0.005). After adjustment for age, gender, asthma status, smoking, and occupational exposure, rhinitis remained significantly associated with an increased risk both for any cough (OR 1.8, 95% CI 1.2-2.6) and for occasional and chronic cough separately (OR 2.2, 95% CI 1.1-4.5, and OR 1.7, 95% CI 1.1-2.6, respectively).

CONCLUSIONS

Rhinitis is a significant and independent risk factor for developing cough among adults. Further research is needed to assess potential implications in terms of prevention.

Idiopathic cough, prevalence and underlying mechanisms

A number of authors have reported a significant percentage of patients whose cause of cough remains undetermined despite a systematic evaluation as recommended in a number of International Guidelines. This subset of patients, which may be regarded as having an idiopathic cough, are often female and of peri or postmenopausal age. Sex hormones may influence the cough reflex in disease or contribute to the chronic lymphocytic airway inflammation seen in some cases and to the association with organ specific autoimmune disease reported. This paper seeks to investigate some of the possible causes of idiopathic cough.

Cough . 6: Which investigations are most useful in the diagnosis of chronic cough?

There is no consensus as to the best diagnostic strategy for chronic cough. Many protocols combine empirical trials of treatment with laboratory investigations. More precise diagnostic tools and improved therapeutic options are required. Until then, the management of chronic cough will remain a clinical challenge.

Idiopathic chronic cough and organ-specific autoimmune diseases: a case–control study

The marked female predominance in cases of idiopathic chronic cough and its association with mild chronic lymphocytic airway inflammation suggests an underlying autoimmune process. We set out to test the hypothesis that idiopathic chronic cough is associated with other organ-specific autoimmune diseases in a case control study. Twenty-two patients with idiopathic chronic cough and 65 community-matched controls for age and sex who responded to a self-administered questionnaire were asked about the presence of autoimmune disease, other medical problems and drug history. All subjects were invited to have a blood test for an autoimmune screen. Thirteen out of 22 (59%) patients with idiopathic chronic cough and eight out of 65 (12%) age- and sex-matched controls reported organ-specific autoimmune disease (odds ratio 8.8; 95% confidence interval 2.4-31.8, P<0.001). Organ-specific autoantibodies were present in a significantly higher proportion of cases than controls (40% vs. 13%; P = 0.047). These findings suggest a relationship between idiopathic chronic cough and organ-specific autoimmunity.

Effect of the second-generation antihistamine, fexofenadine, on cough reflex sensitivity and pulmonary function

AIMS

Current guidelines recommend the use of first-generation antihistamines for the treatment of cough due to rhinitis/postnasal drip syndrome. The antitussive activity of the second-generation antihistamine, fexofenadine, has not been investigated. Therefore, we evaluated the effect of fexofenadine on capsaicin-induced cough in healthy volunteers and in subjects with acute viral upper respiratory tract infection (URI).

METHODS

Twelve healthy volunteers and 12 subjects with URI underwent pulmonary function testing and capsaicin cough challenge on two separate days, 2 h after ingesting 180 mg fexofenadine or matched placebo. Subjects inhaled single, vital-capacity breaths of capsaicin aerosol, administered in incremental doubling concentrations, until the concentration inducing five or more coughs (C5) was determined.

RESULTS

In both subject groups, C5 was not significantly different after fexofenadine compared to placebo. In subjects with URI, pulmonary function studies were also similar. In healthy volunteers, however, FEV1 and FEF(25-75), pulmonary function parameters reflecting the degree of airway dilatation, were significantly increased after fexofenadine. Mean (95% CI) values for FEV1(L) after fexofenadine and placebo were 3.16 (2.77, 3.55) and 3.08 (2.69, 3.47), respectively (P = 0.017). Mean values for FEF(25-75)(L/s) were 3.49 (3.10, 3.88) and 3.26 (2.79, 3.72), respectively (P = 0.029).

CONCLUSIONS

Fexofenadine demonstrated no antitussive activity against capsaicin-induced cough in healthy volunteers and subjects with URI. The ineffectiveness of fexofenadine in suppressing cough probably reflects the lack of anticholinergic activity and central nervous system penetrance that is characteristic of first-generation antihistamines. The mild bronchodilation induced by fexofenadine in healthy volunteers is of unclear clinical significance and requires further investigation.

Eosinophilic bronchitis: clinical features, management and pathogenesis

Eosinophilic bronchitis is a common and treatable cause of chronic cough. The major pathological feature is eosinophilic airway inflammation, similar to that seen in asthma. However, the associated airway dysfunction is quite different, with evidence of heightened cough reflex sensitivity, but no variable airflow obstruction or airway hyperresponsiveness. Recent evidence suggests that the differences in functional association are related to differences in localization of mast cells in airway wall, with airway smooth muscle infiltration occurring in asthma and epithelial infiltration in eosinophilic bronchitis. Diagnosis is usually made with induced sputum analysis after exclusion of other causes for chronic cough on clinical, radiological and lung function assessment. The cough responds well to inhaled corticosteroids but dose and duration of treatment remain unclear. Little is known about the natural history of this condition. However, some patients with COPD without a history of previous asthma have sputum eosinophilia, so one possibility is that some cases of eosinophilic bronchitis may develop fixed airflow obstruction. Further study of this interesting condition will increase our understanding of airway inflammation and airway responsiveness, leading to novel targets for therapeutics for both eosinophilic bronchitis and asthma.

Idiopathic chronic cough: association with organ specific autoimmune disease and bronchoalveolar lymphocytosis

BACKGROUND

We have recently reported a strong association between organ specific autoimmune disease and idiopathic chronic cough and have suggested that cough may be caused by airway inflammation secondary to aberrant homing of activated lymphocytes to the lung. An immunopathological study was undertaken to test the hypothesis that idiopathic chronic cough is associated with lymphocytic airway inflammation.

METHODS

Bronchoscopy, bronchial biopsies, bronchoalveolar lavage (BAL), and peripheral blood and BAL flow cytometry were performed in 19 patients with idiopathic chronic cough, 14 with explained chronic cough, and 11 normal subjects.

RESULTS

Organ specific autoimmune disease or positive autoantibodies were present in eight of the 19 patients with idiopathic cough, in one of the 14 patients with explained cough, and in one of the 11 normal subjects. Median BAL fluid differential lymphyocyte counts were significantly higher in patients with idiopathic cough (10.0%) than in normal subjects (6.3%, 95% confidence interval of difference 1.5 to 11.9, p = 0.01) or patients with explained cough (5.2%, 95% CI of difference 2.0 to 10.4, p = 0.001). There were no differences in bronchial biopsy T lymphocyte counts between the groups. The mean (SE) proportion of CD3+ peripheral blood mononuclear cells expressing CD4 was significantly higher in normal subjects than in patients with idiopathic cough (69 (3)% v 58 (3)%, mean difference 11%, 95% CI of difference 2 to 20, p<0.02) but not than those with explained chronic cough (63 (2)%). There were no differences in BAL T lymphocyte phenotype between groups.

CONCLUSION

BAL fluid lymphocytosis occurs in some patients with idiopathic chronic cough. The association of idiopathic chronic cough with organ specific autoimmune disease raises the possibility that this might be caused by lymphocyte homing from the primary site of autoimmune inflammation or the result of an autoimmune process in the lung.

Cough. 3: chronic cough and gastro-oesophageal reflux

The pathogenesis and clinical features of gastro-oesophageal reflux related cough are complex and the diagnostic tests available are of limited reliability. Treatment needs to be tailored to the specific needs of individual patients and other possible causes of chronic cough should be investigated. Treatment should only be considered to have failed when cough persists after administration of proton pump inhibitors at an adequate dosage for a sufficient length of time.

Cough. 4: Cough in asthma and eosinophilic bronchitis

Airway eosinophilia and cough may be associated with asthma and with non-asthmatic eosinophilic bronchitis. Whether cough variant asthma and eosinophilic bronchitis are distinct entities or a pathophysiological spectrum needs further examination.

Acute cough in the elderly: aetiology, diagnosis and therapy

Although the frequency of physician consultations and the sale of over-the-counter remedies establish the high prevalence of acute cough in the elderly, epidemiological studies have tended to be imprecise. However, respiratory tract infections in nose, larynx and/or bronchi, either viral or bacterial or both, are by far the commonest cause of acute cough. These are especially frequent and hazardous in the elderly, and community living and institutionalisation may aggravate this problem. A variety of viruses and bacteria have been incriminated, with rhinovirus, influenza and respiratory syncytial viruses, and Streptococcus pneumoniae, Haemophilus influenza and Bordetella pertussis being especially important. Viral infections can readily lead to community-acquired pneumonia. Successful diagnosis should point to successful treatment, and in this respect clinical examination and patient history are paramount, supplemented by chest X-ray, viral and bacterial culture and serological testing. Depending on the results of these tests, specific antibacterial therapy may be called for, although there is dispute as to the merits of antibacterial therapy in cases of uncertain diagnosis. Prevention and prophylaxis for influenza and S. pneumoniae infections are now commendably routine in the elderly, especially those in communities. Treatment, as well as the use of antibacterials, may also be directed against the inflammatory and infective processes in the airways. Non-specific antitussive therapy is common and usually highly desirable to prevent the adverse effects of repeated coughing. There have been few advances in antitussive therapy in recent years, opioids and dextromethorphan being the most commonly used agents; they act centrally on the brainstem, but also have a large placebo effect. However they work, they are much appreciated by patients and their partners. Moreover, striking advances in our understanding of the peripheral sensory and central nervous pathways of the cough reflex in recent years should soon lead to a new and more specific choice of agents to inhibit cough.

Sputum eosinophilia in cough-variant asthma as a predictor of the subsequent development of classic asthma

BACKGROUND

A significant proportion of patients diagnosed with cough-variant asthma eventually manifest classic asthma signs, such as wheezing and dyspnoea. The aim of this study was to investigate whether the percentage of eosinophils and/or concentration of eosinophilic cationic protein (ECP) in sputum induced from patients with cough-variant asthma can predict the development of classic asthma.

METHODS

Sixty-two children with cough-variant asthma were prospectively studied for 4 years. At the initiation of the study, sputum was induced with hypertonic saline, and the sputum samples were analysed for total and differential cell counts, and for ECP. Each subject was checked clinically at least every 3 months, and details of classic asthma signs experienced during the intervening periods were taken.

RESULTS

Twenty-four (47.1%) of the 51 subjects available for follow-up developed signs of classic asthma, while 27 did not. The only significant difference in the sputum parameters between these two groups was a higher percentage of sputum eosinophils in subjects who developed classic asthma. A significant association was found between sputum eosinophil percentage and classic asthma development, but not between the concentration of sputum ECP and classic asthma development.

CONCLUSION

Sputum eosinophilia in cough-variant asthma may be a correlate of the later development of classic asthma. This suggests that sputum differential cell counts may be useful in the clinical management of patients with cough-variant asthma, as they may enable the prediction of the subsequent classic asthma development.

Abordagem diagnóstica da tosse crônica em pacientes não-tabagistas: diagnostic approach

A tosse, como mecanismo fisiológico, tem fundamental importância na remoção das secreções respiratórias, constituindo, assim, um dos mecanismos de defesa pulmonar. No entanto, os quadros de tosse crônica constituem uma das principais causas de procura por assistência médica no mundo, o que ressalta o significado da correta identificação e tratamento dos fatores desencadeantes e/ou perpetuadores. Dentre os vários fatores relacionados aos quadros de tosse crônica, alguns assumem papel de relevada importância, tais como o refluxo gastroesofágico, a rinorréia posterior ou a asma, já que, isolada ou conjuntamente, constituem cerca de 95% das causas. O passo fundamental para o sucesso terapêutico nos quadros de tosse crônica é uma abordagem diagnóstica racional, que investigue a tosse crônica de maneira progressiva, permitindo, assim, a instituição do tratamento de forma mais custo-efetiva. Para isso, a proposta de um algoritmo a ser seguido serve como base para essa investigação inicial.

Supra-oesophageal manifestations of gastro-oesophageal reflux disease

Since the early 1960s, many studies have been published that consider the possible relationship between gastro-oesophageal (acid) reflux (GORD) and various other complaints, including dental erosions, ear, nose and throat problems, chronic cough and asthma. Although a high coincidence of GORD and these supra-oesophageal complaints have been noted, there is no consensus on the pathophysiology and management of such complications. In this article we review the literature published between 1966 and 2000 on this subject. We also analyse the available information on the incidence, pathophysiological mechanisms, diagnostic approach and therapeutic options in the various subgroups of disorders.

Cough. 1: Chronic cough in adults

The investigation and treatment of chronic cough in adults is generally rewarding, provided there is an understanding of its aetiology, particularly when it arises from sites outside the respiratory tract.

A study of the cough reflex in idiopathic pulmonary fibrosis

Little is known about the pathogenesis of cough in idiopathic pulmonary fibrosis (IPF). We hypothesized that abnormalities of respiratory tract tachykinin-containing sensory nerves may be implicated. We studied cough response to capsaicin, substance P (SP), and bradykinin in 10 healthy control subjects and 10 patients with IPF. Six patients were tested before and after steroid therapy. Induced sputum cell counts and neurotrophic factor levels were also measured in 13 patients and 13 control subjects. The results show that cough sensitivity to capsaicin was greater in patients (p < 0.01). Neither SP nor bradykinin induced cough in normal subjects. SP and bradykinin induced cough in 7/10 patients (p < 0.002) and 2/10 patients (not significant) with IPF, respectively. Prednisolone caused a reduction in cough sensitivity to capsaicin (p < 0.05) and SP (p < 0.05) in all six patients treated. There were significantly more neutrophils (p = 0.001) and higher levels of nerve growth factor (p < 0.01) and brain-derived neurotrophic factor (p < 0.01) in patient's sputa. These findings suggest functional upregulation of lung sensory neurones in IPF. The cough response to inhaled SP in most patients may reflect disrupted respiratory epithelium. The response to corticosteroids demonstrates that the cough is amenable to therapy.

Induced sputum inflammatory mediator concentrations in chronic cough

Previous studies have shown evidence of airway inflammation in patients with chronic cough and have suggested that the cough may be due to release of tussive mediators and activation of afferent sensory nerve endings. We measured the concentration of various proinflammatory and tussive mediators in induced sputum supernatants from 20 patients with cough variant asthma or eosinophilic bronchitis, 20 patients with nonasthmatic chronic cough, 22 patients with idiopathic chronic cough, and 18 healthy control subjects. We measured histamine, cysteinyl-leukotrienes, prostanoids (prostaglandin D2 and prostaglandin E2), and interleukin-8 by enzyme immunoassay. The median sputum histamine concentrations were significantly higher in patients with idiopathic chronic cough (8.0 ng/ml) and cough variant asthma/eosinophilic bronchitis (10.2 ng/ml) than in normal subjects (2.6 ng/ml; 95% confidence interval of difference from idiopathic chronic cough, 0.8 to 25.8 [p = 0.009] and 95% confidence interval of difference from cough variant asthma/eosinophilic bronchitis, 1.1 to 20.1 [p = 0.01]). Median sputum prostaglandin D2 and prostaglandin E2 concentrations were significantly higher in all categories of chronic cough. Our findings support the view that there is release of inflammatory and tussive mediators in patients with chronic cough and suggest that there might be similarities in the mechanism of cough in a diverse range of conditions.

The role of proton pump inhibitors in the management of gastroesophageal reflux disease-related asthma and chronic cough

Gastroesophageal reflux disease (GERD) occurs in at least one third of patients with asthma and is recognized as a potential trigger for asthma symptoms. The results of studies conducted in patients with both asthma and GERD, in which proton pump inhibitor (PPI) therapy is used to evaluate its effect on asthma outcome, are inconsistent, and many of these studies suffer from different design flaws. However, it does appear that PPI treatment may improve nocturnal asthma symptoms in patients who also have GERD. Moreover, both daytime asthmatic symptoms and pulmonary function seem to improve in some patients with PPI treatment. There is evidence that more severe GERD might predict a more favorable asthma outcome with PPI therapy. For effective management of GERD-related asthma, PPIs should be used at a dose double that of the standard dose for a minimum of 2 to 3 months. Although GERD is also known to be an important cause of chronic cough, there have been only 2 placebo-controlled trials investigating the efficacy of PPI on GERD-related chronic cough. Results of both of these trials suggest that PPI treatment relieves GERD-related chronic cough. As with GERD-related asthma, it would seem reasonable to use a double-standard dose of a PPI for a minimum of 2 to 3 months in the management of GERD-related chronic cough. However, larger, adequately planned studies are needed to confirm the role of PPIs in the management of GERD-related asthma and chronic cough.

Abnormal oesophageal motility in patients with chronic cough

BACKGROUND

Although gastro-oesophageal reflux is a recognised cause of chronic cough, the role of oesophageal dysmotility is unknown. The aim of this study was to determine the prevalence of abnormal oesophageal motility in a selected group of patients with chronic cough.

METHODS

Oesophageal manometry and 24 hour pH monitoring were performed in 43 patients with chronic cough, 34 of whom had symptoms suggestive of gastro-oesophageal reflux. Comparative manometric measurements were made in 21 healthy subjects.

RESULTS

Nine patients with chronic cough had normal manometry and 24 hour pH. Of the remaining 34 patients, 11 (32%) had abnormal manometry alone, five (15%) had abnormal 24 hour pH monitoring alone, and in 18 (53%) both tests were abnormal. Only one patient in the control group had manometric abnormalities.

CONCLUSIONS

These results point to a previously unrecognised high prevalence of abnormal oesophageal manometry in patients presenting with chronic cough. Oesophageal dysmotility may therefore be important in the pathogenesis of cough in these patients.

Psychogenic cough in a schoolboy: evaluation using an ambulatory cough recorder

Psychogenic cough occurs most commonly in patients under 18 years of age. Making the diagnosis on clinical features alone is problematic, and it is usually a diagnosis of exclusion after several negative clinical investigations. We report on the case of a 13-year-old schoolboy with a 3-month history of persistent dry cough with no other associated symptoms. Clinical examination and investigations revealed no abnormality, and empirical trials of antiasthma and antacid medications proved unsuccessful. An objective assessment of his cough frequency was made using an ambulatory cough monitor. A large number of cough episodes were recorded during the day, but during the time he was in bed there were very few episodes recorded. This suggested a diagnosis of psychogenic cough, and he underwent behavior modification therapy under the guidance of a clinical psychologist, with good result. Objective cough monitoring may therefore improve the evaluation and management of chronic cough.

Sputum eosinophilia and bronchial responsiveness in patients with chronic non-productive cough responsive to anti-asthma therapy

OBJECTIVE

We aimed to examine airway inflammation and bronchial responsiveness in patients with chronic non-productive cough responsive to anti-asthma therapy.

METHODOLOGY

Bronchial responsiveness to methacholine as well as the number of inflammatory cells and concentration of eosinophil cationic protein (ECP) in induced sputum were measured in 42 patients with chronic non-productive cough of unknown origin. Their response to bronchodilator, antiallergic and inhaled or oral glucocorticoid therapy was subsequently assessed.

RESULTS

Complete remission of coughing was attained with anti-asthma therapies in 34 patients (responder group), while eight patients did not respond (non-responder group). Twenty patients in the responder group and three in the non-responder group showed bronchial hyperresponsiveness (BHR). The number of eosinophils and ECP levels in the sputum from responders with BHR were significantly increased when compared with those from non-responders and healthy subjects. These sputum measures were also significantly increased in responders without BHR when compared with healthy subjects. However, there were no significant differences in these inflammatory markers between the responders with and without BHR. The neutrophil numbers in the sputum from non-responders and responders both with and without BHR were also significantly higher than in control subjects, but there were no significant differences.

CONCLUSIONS

These findings suggest that patients with chronic non-productive cough responsive to anti-asthma therapy characteristically have eosinophilic airway inflammation, which may play an important role in the development of chronic cough. Furthermore, the evaluation of not only bronchial responsiveness but also airway inflammation by examination of induced sputum may be useful for diagnosis and deciding on therapeutic strategies.

Longitudinal decline in pulmonary function in atopic cough and cough variant asthma

OBJECTIVE

Cough variant asthma and atopic cough are different clinical manifestations of eosinophilic airway inflammation presenting with isolated chronic non-productive cough. The aim of this study was to examine the longitudinal change in pulmonary function in cough variant asthma and atopic cough.

METHODS

Longitudinal change in FEV1 was prospectively examined in 20 patients with cough variant asthma, 14 patients with atopic cough and 271 asymptomatic healthy subjects. All were lifetime non-smokers. Of the 20 cough variant asthma patients, 13 were taking long-term inhaled corticosteroid therapy (ICS) (beclomethasone dipropionate 615 +/- 58 micro g/day) and the other seven were not. Spirometry was taken at first visit, after cough was almost completely relieved on therapy, and at least once every year for 5 or more years afterwards.

RESULTS

The slope of longitudinal change in FEV1 was not significantly different among cough variant asthma patients (- 0.029 +/- 0.007/year), atopic cough patients (- 0.021 +/- 0.022/year) and asymptomatic subjects (- 0.028 +/- 0.002 L/year). In patients with cough variant asthma, the slope in patients not taking inhaled corticosteroids (ICS) was 0.032 +/- 0.007 L/year, which was not significantly different from that in patients taking ICS (- 0.027 +/- 0.010 L/year).

CONCLUSION

Pulmonary function decline is not greater in cough variant asthma than atopic cough and the normal population, and long-term ICS has no effect on the decline in cough variant asthma.

Relief of cough and nasal symptoms associated with allergic rhinitis by mometasone furoate nasal spray

BACKGROUND

Cough commonly occurs as a symptom of seasonal allergic rhinitis (SAR), an inflammatory condition of the nasal mucous membranes that results in rhinorrhea, nasal stuffiness/congestion, nasal itching, and sneezing. Mometasone furoate nasal spray (MFNS, Nasonex, Schering, Kenilworth, NJ), an anti-inflammatory nasal corticosteroid, has been shown to be safe and effective in reducing the nasal inflammation of SAR.

OBJECTIVE

To examine the effectiveness of MFNS in relieving SAR-associated cough, in addition to nasal symptoms.

METHODS

This was a multicenter, randomized, double-blind study. Patients 12 years of age or older with > or = 1-year history of SAR symptoms, positive skin test to a prevailing seasonal allergen, moderate nasal symptoms, and moderate cough were treated for 14 days with MFNS 200 microg daily (n = 122) or placebo (n = 123).

RESULTS

The group treated with MFNS showed significant improvement in the daytime cough severity score at endpoint compared with placebo (P = 0.049). Improvement in the nighttime cough severity score showed a trend in favor of MFNS treatment. Treatment with MFNS significantly improved total nasal symptoms in both the daytime and nighttime compared with placebo at endpoint (P < or = 0.017). Overall daytime symptom scores (cough + total nasal) improved significantly compared with placebo at endpoint (P = 0.005). Overall nighttime symptom scores improved significantly compared with placebo at endpoint (P = 0.028). Treatments were well tolerated, with no significant differences in the incidence of adverse events.

CONCLUSIONS

MFNS is effective and well tolerated in the treatment of daytime cough associated with SAR.

Comparison of atopic cough with cough variant asthma: is atopic cough a precursor of asthma?

BACKGROUND

We have described a group of patients who present with isolated chronic bronchodilator resistant non-productive cough with an atopic constitution, eosinophilic tracheobronchitis, and airway cough receptor hypersensitivity without bronchial hyperresponsiveness, which we have termed "atopic cough". Although cough variant asthma (in which the cough responds to bronchodilators) is recognised as a precursor of typical asthma, it is not known whether atopic cough is also a precursor of asthma.

METHODS

Eighty two patients with atopic cough were retrospectively examined for onset of typical asthma and compared with 55 patients with cough variant asthma (20 untreated patients and 35 treated with long term inhaled beclomethasone dipropionate (BDP), 218-467 micro g/day). The median follow up period for patients with atopic cough and cough variant asthma was 4.8 (1-11.5) years and 3.7 (1-12.4) years, respectively.

RESULTS

Onset of typical asthma occurred in only one of the patients with atopic cough. In patients with cough variant asthma, typical asthma developed in two of 35 patients taking BDP and six of 20 untreated patients (difference 24.3%, 95% CI 2.8 to 45.8, p<0.02).

CONCLUSIONS

These findings suggest that cough variant asthma is a precursor of typical asthma but that atopic cough is not. Treatment with inhaled steroids may prevent the transformation of cough variant asthma into typical asthma.

Measurement of gastric emptying in gastroesophageal reflux-related chronic cough

STUDY OBJECTIVES

Gastroesophageal reflux (GER) is one of the most common causes of chronic cough, but the mechanisms of GER-related cough are not well-understood. We tested the hypothesis that gastric emptying is delayed in patients with GER-related chronic cough.

DESIGN

We studied 12 patients (7 women; mean age, 53 years; age range, 37 to 68 years) with GER-related chronic cough and a control group of 27 asymptomatic healthy volunteers (16 women; mean age, 37 years; age range, 18 to 62 years). Gastric emptying scintigraphy was performed, and the time at which 50% of the radiolabeled material had left the stomach (T(1/2)) was calculated.

RESULTS

There was no statistically significant difference in T(1/2) values between healthy volunteers and subjects with GER-related cough (99 +/- 26 min vs 86 +/- 20 min, respectively; difference between the means, 13 min [95% confidence interval, -4 to 30 min]; p = 0.13).

CONCLUSIONS

Gastric emptying was not delayed in patients with GER-related chronic cough. The measurement of gastric emptying did not therefore provide further insights into the mechanisms of GER-related cough or clinically relevant information that would assist in patient management.

Epidemiology of cough

Patients with cough may be conveniently divided into those with acute, usually viral, illness and those with chronic cough. Acute cough represents the largest single cause of consultation in primary care, whereas chronic cough is one of the commonest presentations in respiratory medicine. The world-wide market in cough treatments is several billion dollars. In both syndromes, cough sensitivity is upregulated, but the inflammation giving rise to cough is localised to the larynx and large airways in acute cough. Whilst this is also true of cough-predominant asthma, the origin of cough in chronic disease may also lie in the oesophagus, nose or sinuses leading to errors in diagnosis and treatment.

Central pathways for cough in man--unanswered questions

Central processing of afferent cough impulses occurs in a putative 'cough centre' in the dorsal medulla where the reflex is subject to considerable cortical control. Little is known about the central neurotransmitters and mediators which mediate cough in humans. Previous animal and human studies suggest that the antitussive effect of opiates may be mediated at central 5-HT receptors. In three studies in healthy human volunteers, we have investigated the potential role of central cholinergic and dopaminergic receptors in the mediation of cough, and the potential role of 5-HT receptors in the antitussive action of opiates. Intravenous administration of atropine or physostigmine had no effect on capsaicin-induced cough. Similarly, oral administration of L-dopa, bromocriptine or haloperidol had no effect on capsaicin-induced cough. Compared with saline, intravenous morphine significantly suppressed capsaicin-induced cough and increased drowsiness. Compared with placebo, pretreatment with oral pizotifen significantly attenuated the antitussive effect of morphine, but not the sedative effect. This suggests that in humans, an agonist action at 5-HT2 and/or 5-HT1 receptors may be involved in the antitussive effect of morphine, but not its sedative effect. Further knowledge of central cough pathways in humans must await the availability of more selective receptor agonists and antagonists for human studies. This offers the promise of effective antitussive therapy. The challenge is to find an antitussive agent which can return the abnormal sensitivity of the cough reflex to normal, without adverse effects.

Gastroesophageal reflux as cause of chronic respiratory symptoms

OBJECTIVE

Gastroesophageal reflux (GER) is a relatively common disorder in infants and children. It maybe associated with severe complications. The coexistence of GER and a wide range of respiratory symptoms has been reported. The purpose of our study was to investigate the relationship between chronic respiratory symptoms and GERD as an underlying cause. To our knowledge, there is not a method known study for identifying this relationship and prevalence in our area.

METHODS

The study group consists of fifty-two (4 months-10 years) children who were referred to pediatric surgery ward for evaluation of GERD as a cause of chronic respiratory symptoms by 24 hours PH monitoring. Additionally, 10 patients with only one episode of pneumonia were evaluated as the control group. Chronic respiratory presentations include the following: chronic cough, recurrent pneumonia, asthma, and respiratory distress.

RESULTS

24 hour esophageal PH monitoring revealed GER in 22 (42.2%) patients as a cause of their chronic respiratory symptoms, while (30 (57.7%) children did not show any evidence of GER. GER was detected in 11 of 24 (45.7%) patients with chronic cough. Thirty-three patients presented with recurrent pneumonia, 13 (39.9%) of whom had GER. In 8 patients with asthma, GER was found in 4 cases. None of the 6 patients with respiratory distress had GERD.

CONCLUSION

The possibility of GERD was significantly higher in study group (children with chronic respiratory symptoms) compared to control group (p-value<0.01). All patients with chronic cough, recurrent pneumonia and asthma should be aggressively investigated for the possibility of GER. Documenting abnormal gastroesophageal reflux helps direct appropriate therapy before occurrence of major complications.

Comparisons of peak diurnal expiratory flow variation, postbronchodilator FEV(1) responses, and methacholine inhalation challenges in the evaluation of suspected asthma

STUDY OBJECTIVES

The validity of peak expiratory flow variation (PEFvar) as defined by National Heart, Lung, and Blood Institute (NHLBI) guidelines as a diagnostic tool for suspected asthma or its comparative value to methacholine inhalation challenge (MIC) or postbronchodilator (BD) FEV(1) responses has not been formally assessed. We prospectively analyzed the correlation of 28 different PEFvar indexes (including 4 NHLBI-compatible indexes) with MIC and pre-BD and post-BD FEV(1) responses in suspected asthmatic subjects with normal findings on lung examination, chest radiography, and baseline spirometry.

DESIGN

Participants were asked to record peak expiratory flow four times daily for 2 to 3 weeks, followed by an MIC. During a minimum 6-month follow-up period, a clinical diagnosis of asthma was made or ruled out based on testing results and response to antiasthma therapy.

SETTING

Medical school-affiliated subspecialty private practice of allergy, asthma, and immunology.

PARTICIPANTS

One hundred twenty-one suspected asthmatic patients with normal findings on lung examination, chest radiography, and baseline spirometry.

MEASUREMENTS AND RESULTS

Fifty-seven subjects completed both the peak flow diary and the MIC and were accepted for statistical analysis. There were no statistically significant correlations between any peak expiratory flow index and MIC. Among the three diagnostic tools evaluated, MIC had the highest sensitivity (85.71%). All the PEFvar indexes and post-BD responses had low sensitivity and high false-negative rates.

CONCLUSIONS

PEFvar and post-BD FEV(1) responses are poor substitutes for MIC in the assessment of patients with suspected asthma with normal findings on lung examination, chest radiography, and spirometry. Our findings warrant a reconsideration of the NHLBI guidelines recommendation of the utility of PEFvar as a diagnostic tool for asthma in clinical practice.

Is there an association between angiotensin-converting enzyme gene variants and chronic nonproductive cough?

BACKGROUND

It is unclear why some patients develop a chronic nonproductive cough. Angiotensin-converting enzyme (ACE) inactivates tussive peptides in the airways such as bradykinin and tachykinins. An insertion/deletion polymorphism in the ACE gene accounts for variation in ACE levels, and patients with the II genotype have lowest serum ACE levels compared with ID and DD genotypes. We hypothesized that the II genotype would be associated with increased risk of developing a chronic cough.

MATERIALS AND METHODS

We recruited 47 patients (33 women), referred for evaluation of cough (median cough duration, 24 months; range, 2 to 240 months). Cough patients were evaluated using a comprehensive diagnostic protocol, and cough reflex sensitivity was measured using a capsaicin inhalation challenge. ACE genotyping was performed on DNA samples from patients using the polymerase chain reaction followed by agarose gel electrophoresis. ACE genotypes in patients with chronic cough were compared with those in 199 healthy control subjects. Serum ACE levels were determined using a colorimetric assay.

RESULTS

Genotype frequencies for the ACE gene were similar between patients and control subjects. There was no correlation between capsaicin sensitivity and ACE genotypes or serum ACE levels.

CONCLUSION

Susceptibility to develop chronic cough is not associated with ACE genotype.