ROLE OF SPIROMETRY IN COUGH–VARIANT ASTHMA IN HO CHI MINH CITY, VIET NAM.

Introduction: By definition of GINA-2002, patients with cough-variant asthma have chronic cough as their principal symptom. Frequently the cough occurs at night so that evaluations during the day can be normal .¹ There are 3 recommended ways to diagnose the cough-variant asthma: documentation of variability in lung function or of airway hyperresponsiveness and search for sputum eosinophils.¹ Because of the limitations of these three methods and the lack of facilities in Vietnam, we use the method of spirometry with bronchodilator test to detect cough-variant asthma. This method has found widespead acceptance for use in asthmatic patients over 5 years of age, but its role in cough-variant asthma is not well documented.

Materials: Among 1428 patients who came to our pulmonary function laboratory to have spirometric test done, with various purposes, from November 2001 to April 2002, 103 patients have been diagnosed as having cough-variant asthma. Those patients have chronic cough, with or without ches tightness but no wheezing. The spirometric tests were adhered to the method of ATS, 1994 .² The brochodilator test was performed for all these patients in the first time. A second spirometric test was performed after 2 weeks of treatment and every 3 months later, if possible. The diagnosis of variant-cough asthma by spirometry was made when at least a 12 per cent improvement in FEV₁or 15% increase in PEF (on flow-volume curve), after inhalation of 200 mgr of salbutamol sulfate or in response to a trial of glucocorticoid therapy. Patients who stopped coughing after glucorticoid treatment with normal spirometric recordings, before and after the treatment, were also diagnosed as cough-variant ashma.

Results & discussion: The result of 103 patients showed that there are 3 types of spirometric responses:

Table 1. Three types of spirometric responses in cough-variant asthma

Thus in our study, the spirometry is useful in diagnosis of cough-variant asthma up to 92% of cases. Those patients have been diagnosed as tonsillitis, sinusitis, pharyngitis, or chronic brochitis and have been treated inappropriately with successive courses of antibiotics and cough medications. They have suffered the cough from 2 weeks to 33 years before the diagnosis of cough-variant asthma is made. But caution must be made for other differential diagnosis as active tuberculosis, gastroesophageal reflux, use of ACE inhibitor and psychologic cough. With the diagnosis as cough-variant asthma and appropriate asthmatic treatment, the symptoms generally disappear after 2 weeks of treatment, the quality of life of patients usually markedly improved. The high positive result of spirometry in cough-variant asthma in Vietnam may reflect a reality that the diagnosis of cough-variant asthma have been delayed for a substantially long time.

Conclusion: Although the spirometry with bronchodilator test is not widely recommended as a mean to detect cough-variant asthma, we found that it is a very effective method in Vietnam. The result of 92% of patients with cough-variant asthma have had positive response on spirometric recordings in Vietnam may reflect the great delay in making the diagnosis of cough-variant asthma in this country. We suggest that the spirometry with bronchodilator test should be recommended as a tool in diagnosis of cough-variant asthma, especially in developing countries.

References:
1. Claude Lenfant – Global strategy for asthma management and prevention: Diagnosis and classifiaction 2002 – p: 67 ? 76

2. ATS Statement – Standardization of spirometry – 1994 Update, Am J Respir Crit Care Med, Vol 152 pp 1107 – 1136, 1995