Asthma is a syndrome with a collection of symptoms. The history should record the nature, duration, frequency and severity of symptoms. It should also seek to identify triggers (i.e. aggravating and precipitating factors), associated diseases, family history and the patient's occupation.
| Clinical features that increase the probability of asthma |
- Widespread wheeze heard on auscultation of the chest
- Increased expiratory time
- Hyperinflation
- Otherwise unexplained reduced forced expiratory volume/1 second recording (FEV1) or Peak expiratory force recording (PEFR) (historical or serial readings)
- Otherwise unexplained peripheral blood eosinophilia
- Raised sputum eosinophil count (specialist centres only)
- Raised exhaled nitric oxide measurement (fENO)
| Clinical History |
- More than one of the following symptoms: wheeze, cough,difficulty breathing, chest tightness, rhinitis and particularly if :
- Symptoms are worse at night and in the early morning
- Symptoms in response to exercise, allergen exposure and cold air
- Symptoms after taking aspirin or beta-blockers
- Personal history of atopic disorder
- Family history of atopic disorder and/ or asthma
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| Clinical features that lower the probability of asthma |
- Prominent dizziness, light-headedness, peripheral tingling
- Chronic productive cough in the absence of wheeze or breathlessness
- Repeatedly normal physical examination of chest when symptomatic
- Voice disturbance
- Symptoms with colds only
- Significant smoking history, i.e. more than 20-pack years
- Cardiac disease
- Normal PEFR or spirometry when symptomatic*
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*normal spirometry when not symptomatic does not exclude the diagnosis of asthma. Repeated measurements of lung function are often more informative than a single assessment.
Adapted from British Thoracic Society (BTS) Scottish Intercollegiate Guidelines Network (SIGN) 101. British Guideline on the Management of Asthma: a national clinical guideline. 2009.
Available from http://www.sign.ac.uk/guidelines/fulltext/101/index.html
Lung function tests
Performance and interpretation of lung function tests in older adult patients may be more challenging because of the impact of age-related respiratory physiological and anatomical changes on lung function.
In older age, the chest wall becomes stiffer and less compliant and age-related osteoporosis can lead to changes in the shape of the thorax, leading to greater dorsal kyphosis and anteroposterior diameter. As a result, not only is the chest wall more fixed, but the contained lungs are left at a mechanical disadvantage. Furthermore, nutritional status (which is often deficient in older patients) frequently contributes to altered respiratory muscle strength.
The net effect is that older patients breathe at higher lung volumes than younger patients. Apparent "fixed obstruction" may, as a result, be observed in the interpretation of lung function tests of people with long-standing asthma versus late-onset counterparts. The same notion is not only demonstrated in asthma, but is also seen in COPD. Age-dependant physiological changes in pulmonary function, particularly age-related decreased elastic recoil, contribute additionally to clinical difficulty in differentiating asthma from COPD from lung function tests. However, spirometry remains the key initial diagnostic test to assess the presence and severity of airflow obstruction.
Consequently, approximately 20% of people with asthma are misdiagnosed, so care must be taken when interpreting the results of lung function test.
| Diagnostic tool |
Findings that support diagnosis |
| Reversibility testing with spirometry or PEFR |
Demonstration of reversible airflow limitation:
- FEV1 improves at least 12% and 200 ml either spontaneously, after inhaled bronchodilator, or after trial of corticosteroid therapy; OR
- PEFR improves at least 15% after inhaled bronchodilator or after trial of corticosteroid therapy.
(Note: Postbronchodilator FEV1/FVC < 0.70 suggests COPD in adults, but may lead to over-diagnosis of COPD and obstructive lung disease in older patients with asthma.)
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| Exercise challenge with spirometry or PEFR |
Demonstration of airway hyperresponsiveness:
- FEV1 decreases at least 15% from baseline after 6 minutes of exercise; OR
- PEF decreases at least 20% from baseline after 6 minutes of exercise.
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| Home PEFR diary (if needed) |
Demonstration of variable airflow limitation:
- PEFR varies more than 20% from morning measurement upon arising to measurement 12 hours later in patients taking a bronchodilator (more than 10% in patients not taking a bronchodilator).
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Adapted from Global Initiative for Asthma (GINA). Pocket Guide for Asthma Management and Prevention in Adults & Children over 5 (2004).
Available from http://www.ginasthma.org.
| Potential barriers to performing effective lung function tests in older adults |
| Cognitive impairment (unable to follow technician instructions) |
| Fatigue and comorbid medical conditions (e.g., cardiovascular, thyroid disease) |
| Impaired coordination (e.g. Parkinson's disease, stroke) |
| Mouth or dental problems (e.g. dentures, ulceration) |
| Main difficulties for clinicians when interpreting Lung function tests for older adults |
| Age-related physiological changes (vital capacity, residual volume, and functional residual capacity) |
| Overpredicted "extrapolated" reference FEV1 and FVC values |
| Standard FEV1/FVC cutoff of 70% for airflow obstruction leading to overdiagnosis of obstruction in older patients |
| Airway remodelling contributing to "fixed obstruction" easily mistaken for COPD |
| Concurrent asthma and COPD |
Therapeutic trial
When clinical judgement indicates a high probability of asthma, but reversibility is not demonstrated on spirometry, a therapeutic trial with inhaled corticosteroid therapy (200-400mcg beclomethasone equivalent, daily) may be useful to confirm a diagnosis. The patient's symptoms should be monitored for improvement for 6-8 weeks. If symptoms recur on stopping therapy a diagnosis of asthma can be established.
Allergy skin testing
Skin-prick testing is used to confirm reaction to an allergen. A drop of liquid containing the allergen is placed on the skin (usually 15-30 concurrent tests for the most common allergens), then the skin is pierced with a lancet. If the individual is hypersensitive a hive will form within 2 minutes.
IgE testing (radioallergosorbent test/IgE specific immunoassay –RAST testing)
Specific IgE testing is helpful where skin-prick testing cannot be performed, e.g. presence of eczema. The blood test measures the amount of IgE antibody in the blood for the suspected allergen(s) and is very specific.
Chest X-Ray
Chest x-rays are not normally indicated in the normal assessment of suspected asthma and should only be considered if clinical signs indicate another condition e.g. carcinoma, pneumothorax, foreign bodies.
Red Flags and differential diagnoses
Symptoms typical of asthma, such as intermittent wheezing, breathlessness, and cough can also indicate other respiratory problems in older patients, particularly chronic obstructive pulmonary disease (COPD). Similarly, other symptoms of asthma, such as chest pain or tightness, may be due to non-pulmonary disease (e.g. ischemic heart disease, heart failure, anaemia, or pulmonary embolism).
When a patient remains symptomatic despite optimal prescribed treatment and confirmation of effective inhaler technique and good compliance, then referral to secondary care or specialist respiratory services should be considered.
Differential diagnoses
| Differential diagnosis of asthma in adults, according to the presence or absence of airflow obstruction (FEV1/FVC<0.7) |
| COPD |
| Chronic cough syndromes |
| Hyperventilation syndrome |
| Vocal cord dysfunction |
| Rhinitis |
| Gastro-oesophageal reflux |
| Heart failure |
| Pulmonary fibrosis |
| With airflow obstruction |
| COPD |
| Bronchiectasis* |
| Inhaled foreign body* |
| Obliterative bronchiolitis |
| Large airway stenosis |
| Lung cancer* |
| Sarcoidosis |
*May also be associated with non-obstructive spirometry
| Indications for specialist referral in adults |
| Diagnosis unclear |
| Unexpected clinical findings (i.e. crackles, clubbing, cyanosis, hypoxaemia, cardiac disease) |
| Unexplained restrictive spirometry |
| Suspected occupational asthma |
| Persistent non-variable breathlessness |
| Monophonic wheeze or stridor |
| Prominent systemic features (myalgia, fever, weight loss) |
| Chronic sputum production |
| CXR shadowing |
| Marked blood eosinophilia (>1 x 109/L) |
| Poor response to asthma treatment |
| Severe asthma exacerbation |
Adapted from British Thoracic Society (BTS) Scottish Intercollegiate Guidelines Network (SIGN) 101. British Guideline on the Management of Asthma: a national clinical guideline (2009).
Available at http://www.sign.ac.uk/guidelines/fulltext/101/index.html
Completion of the short Differential diagnosis questionnaire (approximately 1 minute completion time) will help evaluate the possibility of asthma and COPD in adult patients over the age of 40 years who have never smoked OR have a prior diagnosis of respiratory disease or current regular respiratory treatment. It will not produce a definitive diagnosis, but may help determine whether a diagnosis of asthma or COPD is more likely in an individual.