What Is Cough Variant Asthma?

Cough Type Asthma is also known as Cough variant asthma (CVA). In 1972, Gluser first reported the disease and named it variant asthma. It refers to chronic cough as the main or only clinical manifestation. A special type of asthma. GINA (Global Asthma Prevention Initiative) clearly considers cough variant asthma to be a form of asthma. Its pathophysiological changes, like asthma, are also sustained airway inflammatory responses and airway hyperresponsiveness. When the onset of bronchial asthma begins, 5% to 6% are with persistent cough as the main symptom, which mostly occurs at night or in the early morning, and is often an irritating cough. The age of onset is higher than that of typical asthma. About 13% of patients are older than 50 years old, and it is more common in middle-aged women. In childhood, cough may be the only symptom of asthma, and even a precursor to the development of bronchial asthma, and the number of patients in the hospital has increased significantly.

Basic Information

nickname

Cough variant asthma

English name

Cough Type Asthma

English alias

Cough Variant Asthma, CVA

Visiting department

Respiratory

Multiple groups

Middle-aged woman

Common causes

Genetics, immune status, psycho-psychological status, endocrine and health status, as well as allergens, viral infections, occupations, climate, drugs, exercise and diet, etc.

Common symptoms

Long-term refractory dry cough

Causes of cough asthma

The causes of cough asthma are intricate and complicated. In addition to subjective factors such as the patient's own genetic qualities, immune status, psycho-psychological status, endocrine and health status, allergens, viral infections, occupational factors, climate, drugs, exercise and diet Other environmental factors are also important reasons for the development of asthma.

Clinical manifestations of cough asthma

Because cough variant asthma has cough as the only symptom, the clinical characteristics lack specificity and the misdiagnosis rate is very high. Therefore, the possibility of chronic recurrent cough should be thought of. Because 50% to 80% of children with cough variant asthma can develop typical asthma, and 10% to 33% of adults can develop cough variant asthma. Many authors consider cough variant asthma a precursor to asthma Performance, so early diagnosis and early treatment of cough variant asthma is very important to prevent asthma. It has the following clinical characteristics:

Affected population

The incidence is higher in children, and dry cough has been found to be associated with cough variant asthma in more than 30% of children. In adults, the age of onset of cough variant asthma is higher than that of typical asthma. About 13% of patients are older than 50 years, and it is more common in middle-aged women.

2. Symptoms

Cough may be the only symptom of asthma, mainly long-term refractory dry cough, which is usually induced after inhaling irritating odor, cold air, contact with allergens, exercise or upper respiratory tract infection, and some patients have no incentive. Intensified at night or early in the morning. Some patients have a certain seasonal attack, mostly in spring and autumn. Most patients have been treated with antitussive and phlegm drugs and antibiotics for a period of time at the clinic, which has almost no effect, but can be relieved with glucocorticoids, antiallergic drugs, 2 receptor agonists and theophylline.

3. History of allergies

The patient may have a clear history of allergic diseases, such as allergic rhinitis and eczema. Some patients can be traced back to a family history of allergies.

Cough asthma test

Blood routine

Peripheral blood eosinophils increased during the attack.

2. Imaging examination

With no abnormalities, CT can help rule out early-stage lung disease and atypical bronchiectasis.

3. Measurement of lung function and airway responsiveness

It is an important indicator for diagnosis of CVA and judgment of curative effect. The degree of pulmonary function decline in CVA patients is not as obvious as in typical asthma, and most patients have normal pulmonary ventilation function, so it is difficult to make a judgment based on changes in lung function alone. In view of the characteristic of AHR in CVA, patients with suspected CVA can be tested with bronchial provocation or bronchiectasis. For the 1st second forced expiratory volume (FEV1)> 70%, the bronchial provocation test was performed; for FEV ₁ <70%, the bronchodilator test was performed; in addition, the peak expiratory flow rate (PEF) was measured using a peak expiratory flow meter, It is a simple and portable method for dynamic monitoring of lung function. It is easy to operate and cheap. The positive judgment criterion is a daily (or 2 weeks) mutation rate of 20%. CVA is diagnosed by positive judgment as airway hyperresponsiveness.

4. Evaluation of airway inflammation

The pathological changes of CVA are airway inflammation, so detecting airway inflammation indicators plays an important role in judging airway inflammation and assisting diagnosis.

(1) Induced sputum (IS) is feasible for classification of sputum cells and detection of soluble substances in sputum, which reflects the condition of airway secretions. Among the cells involved in CVA airway inflammation, the infiltration of eosinophils is the most obvious, which induces Changes in acid granulocytes can predict the development of CVA into typical asthma.

(2) Bronchial bronchoscopy and alveolar lavage mainly reflect the inflammation of the peripheral airways below the lung sub-segment. Bronchial mucosal biopsy can directly obtain the pathological basis of airway inflammation.

(3) Exhaled nitric oxide (FENO) FENO is related to airway inflammation and AHR in eosinophils. The levels of FENO in patients with CVA and asthma are significantly higher than those caused by chronic cough due to other causes. Therefore, FENO has high sensitivity and specificity for the diagnosis of CVA, and has important application value in the diagnosis of the etiology of chronic cough.

(4) Non-invasive detection technology of exhaled breath condensate (EBC) , compared with induced sputum, bronchoalveolar lavage, etc., has the characteristics of real-time, simple and repetitive, which can dynamically detect airway inflammation.

5. Signs

Although it may also have bronchospasm, it usually occurs in small bronchi or transient spasms at the periphery, so wheezing is rarely or rarely heard during physical examination.

Cough Asthma Diagnosis

The possibility of asthma should be considered when encountering patients who only complain of chronic cough (greater than 3 weeks). Currently recognized diagnostic standards in China:

1. Cough persists or recurrent for more than 1 month, less sputum, worsening after exercise, but no wheezing;

2. Symptoms often occur in the early morning, at night or at bedtime;

3. Seasonal onset or exposure to irritating odors will cause airway hyperresponsiveness symptoms such as belching, unbearable cough, and intolerance;

4. Exclude other chronic respiratory diseases;

5. After antibiotics and symptomatic treatment for> 2 weeks, symptoms did not improve, but anti-allergy and bronchodilators were effective;

6. With one or more of the following allergic diseases or medical history, previous history of allergic rhinitis or allergic bronchitis, elevated peripheral blood eosinophils or serum immunoglobulin E (IgE)> 200mg / L, sputum Large number of eosinophils, positive skin allergen test, and family history of asthma

7. Bronchodilation test or provocation test is positive, or 24-hour peak expiratory flow rate (PEF) mutation rate is positive.

Differential diagnosis of cough asthma

Because many diseases can cause cough, the diagnosis of CVA must exclude the following common diseases: acute and chronic bronchitis, bronchial tuberculosis, allergic cough, bronchodilation, upper airway cough syndrome, gastroesophageal reflux, taking angiotensin Cough caused by invertase inhibitors.

Cough Asthma Treatment

Treatment principle

CVA is treated in the same way as typical bronchial asthma. The American ACCP (American College of Chest Physicians) guidelines suggest that the vast majority of CVA patients are effective for inhaled bronchodilators and inhaled corticosteroids. China's cough guidelines recommend that most CVA patients can inhale small doses of glucocorticoids combined with bronchodilators ( ₂ receptor agonists or aminophylline, etc.), or a combination of both. Similar to typical asthma, short-term oral low-dose glucocorticoid therapy may be equally effective in patients with CVA. CVA treatment time should be no less than 8 weeks. Studies suggest that 30% to 54% of CVA patients can develop into typical asthma without intervention, and early inhaled glucocorticoid therapy can effectively reduce the risk of CVA progressing to typical asthma, so early standardized treatment based on inhaled hormones It is of great significance to improve the prognosis of CVA patients. Because of the idiopathic nature of many CVA patients, avoiding exposure to corresponding allergens is also important to prevent the progression of CVA.

2. Drug treatment

Mainly for the application of anti-inflammatory drugs and bronchodilators.

(1) Bronchodilators For patients with intermittent cough symptoms, bronchodilators can be used as needed, mainly short-acting ₂ receptor agonists or theophylline. For those who have frequent and frequent cough symptoms or inhaled glucocorticoids still cannot effectively control the symptoms, a long-acting ₂ receptor agonist or slow-release theophylline can be added.

(2) Inhaled glucocorticoids Because CVA has eosinophilic airway inflammation and airway remodeling as typical asthma, inhaled glucocorticoids (ICS) is its first-line treatment. Inhaled hormonal treatment should be started as soon as possible after diagnosis of CVA . Foreign guidelines generally recommend the use of budesonide or fluticasone propionate, and higher doses may be required in some cases. If inhaled glucocorticoid treatment alone does not relieve symptoms, bronchodilator therapy should be combined. For most patients with CVA, ICS treatment can quickly relieve cough symptoms. After cough relief, gradual reduction and step-down treatment can be considered. However, cough may recur after ICS treatment is discontinued. Some scholars have suggested that long-term ICS treatment should be given to CVA patients to prevent the progression to typical asthma and airway remodeling, but its effectiveness remains to be confirmed by prospective studies.

(3) Leukotriene Receptor Antagonist The CVA treatment plan recommended by the British Thoracic Society includes short-acting beta ₂ receptor agonists, inhaled hormones, and leukotriene receptor antagonists. The United States ACCP guidelines recommend that CVA patients who have poor efficacy with inhaled hormones and bronchodilators, after excluding influencing factors such as poor compliance, can be increased with leukotriene receptor antagonist treatment before oral hormone therapy. Several studies have reported that anti-leukotriene receptor antagonist therapy is effective for CVA patients in alleviating cough symptoms, reducing airway inflammation, and improving lung function, but the number of observations is relatively small. Since leukotriene receptor antagonists have not been proven to prevent airway remodeling and progression to typical asthma, it is best to use leukotriene receptor antagonists in combination with ICS. Leukotriene receptor antagonist monotherapy should be considered in patients with CVA who cannot tolerate or comply with ICS.

(4) Oral glucocorticoids. When patients with CVA cannot use ICS treatment to effectively control the acute exacerbation of the disease, or patients with persistent cough due to inhaled hormones may consider short-term oral hormone therapy, the general course of treatment is 1 to 2 weeks, and then continue inhaled hormone therapy. Monitoring of airway inflammation following routine treatment for CVA shows that patients with persistent eosinophilic airway inflammation are more likely to benefit from upgraded anti-inflammatory treatments.