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PaulaKauppi

Asthma: Symptoms and Diagnosis

Essentials

  • Asthma is an inflammatory disease of the airways, associated with reversible bronchoconstriction.
  • Common symptoms of asthma include prolonged cough, mucus production, dyspnoea and wheezing.
  • The inflammation increases the sensitivity of the airways to many irritants.
  • Auscultation of the lungs, spirometry, bronchodilatation test, peak expiratory flow (PEF) monitoring, chest x-ray, blood eosinophil count and allergy tests are the basic examinations. Other examinations may be performed in uncertain cases or when a more exact classification of the disease is pursued.
  • Detecting a reversible bronchoconstriction in even only one examination (spirometry, PEF monitoring, methacholine test, exercise challenge test) is enough to diagnose asthma.

Epidemiology

  • Asthma affects about 6-9% of the population.
  • Asthma is particularly common among children and those aged 40 years or over.

Symptoms

  • The symptoms of asthma often vary even in one single patient from month to month.
  • Prolonged cough
    • Especially in the early hours and in the mornings
    • In association with irritating factors
    • For about one-third of patients with persistent cough an asthma diagnosis is set later.
    • The cough may be dry, but often clear mucus is excreted from the lower respiratory tract.
  • Wheezing
    • Simultaneously with dyspnoea
  • Dyspnoea
    • In association with upper respiratory tract infections
    • After exercise (especially in cold weather)
    • After exposure to allergens such as pollen and animal dander
    • In the early hours and in the mornings
  • For differences between asthma and COPD, see table T1. A patient's disease may also be a combination of asthma and COPD.

Differences between asthma and COPD

Disease characteristicsAsthmaCOPDAsthma and COPD
AetiologyUnknown, atopySmokingAtopy and smoking
OnsetOften rapidSlowOften asthma diagnosed at < 40 years of age
DyspnoeaParoxysmalOn physical exertionBoth paroxysmal and on physical exertion
ObstructionVariableProgressive, constantBoth variable and constant
Eosinophilic leukocytes in sputumOften presentRarely presentOften present
Response to bronchodilating drugsStrongWeakStrong
Course of the diseaseVariableProgressiveOften more symptoms and exacerbations than in a person with only asthma or only COPD

Diagnostic approach

  • Asthma can be strongly suspected on the basis of history and auscultation (audio sample Wheezing of Asthma). Demonstration of varying degrees of bronchoconstriction by pulmonary function tests is required to confirm the diagnosis (table T2).
  • The standard diagnostic investigations can be performed in primary care.
  • If recurrent episodic or continuous medication is required, the baseline situation should be assessed thoroughly and the diagnosis should be certain. This enables the doctor to compare the later course of the disease with the baseline situation. Find out about local requirements concerning reimbursement of medication..
  • If the symptoms in the initial stage are severe, drug therapy must be started immediately, and simultaneous PEF monitoring can be used as a diagnostic test alongside symptoms and signs.
  • If the asthma diagnosis remains uncertain, one can consider pausing the therapeutic medication, at a later point of time, for a period of at least 4 weeks so that new diagnostic pulmonary function tests can be carried out.

Auscultation of the lungs

  • The respiratory sounds should also be auscultated during rapid and forceful expiration.
  • End-expiratory wheezing Wheezing of Asthma is nearly always a sign of an obstructive disease such as asthma.
  • In mild incipient asthma the auscultation is usually normal when the patient is asymptomatic.
  • The auscultation may occasionally be normal even in a patient with excessive symptoms.

Pulmonary function tests

  • See table T2.
  • Spirometry Pulmonary Function Tests gives more accurate information on pulmonary function than PEF.
    • In mild or incipient asthma, the spirometry results may be normal.
  • PEF measurement Pulmonary Function Tests is the simplest available asthma investigation in the diagnostic phase, but it requires a good blowing technique.
    • The result is usually normal in incipient asthma during an asymptomatic phase.
  • Moderate to strong hyperreactivity observed in a metacholine challenge test is diagnostic for asthma.
    • Some other tests for measuring unspecific hyperreactivity of the bronchi are available in specialized clinics.
  • Running in the open air, especially in cold weather easily triggers bronchoconstriction in asthmatic patients. This can be utilized in a running exercise test.

Pulmonary function tests in the diagnosis of asthma

TestCriteria of diagnostic findingPractical method(s)
Spirometry
  • Significant bronchodilatation response: 12% and 200 ml improvement in FEV1 or FVC
  • FEV1 improves 15% and 200 ml during asthma treatment in long-term follow-up.
PEF monitoring
  • In 2-week PEF monitoring, 3 times a significant bronchodilatation response or 24-hour variation
  • Significant bronchodilatation response: 15% and 60 l/min
  • Significant 24-hour variation: 20% ja 60 l/min (see program Pef Calculator)
  • Average PEF level increases 20% and 60 l/min during asthma treatment in long-term follow-up.
  • The patient measures the PEF value in the morning and later in the afternoon for 2 weeks. Three consecutive, forceful, brief blows are performed.
  • All the three results are recorded; the best one is used for evaluation.
  • The blows are repeated 15 minutes after the administration of a bronchodilating drug (salbutamol 400 µg or terbutaline 1 mg).
  • Additionally, it is important to perform PEF measurement always when asthma symptoms appear (on exertion or allergen exposure, or in the night). The blows are performed in the same way as in the morning or evening.
  • Provide the patient with adequate instructions and a tracking chart.
Metacholine challenge test
  • Moderate or strong bronchial hyperreactivity
Exercise test*
  • FEV1 or PEF decrease at least 15%.
  • After PEF or FEV1 recording the patient runs out of doors for 6 min, the lungs are auscultated and PEF or FEV1 value is recorded immediately after the exercise and repeatedly after 5, 10 and 15 min.
Trial of glucocorticoid therapy
  • Average PEF level increases 20% and 60 l/min during asthma treatment in long-term follow-up.
  • FEV1 improves 15% and 200 ml during asthma treatment in long-term follow-up.
  • Oral prednisolone 20-40 mg/day is prescribed for 1 week in the exacerbation period of asthma. Alternatively, inhaled beclomethasone or budesonide 0.8 mg/day, fluticasone 0.5-1.0 mg/day or ciclesonide or mometasone in respective doses; in which case the follow-up time must be 8 weeks (see table of clinically comparable doses of inhaled glucocorticoids in Long-Term Management of Asthma).
  • Spirometry is performed at the start and end of treatment. Morning and evening PEF values are monitored for one week at the beginning and another week at the end of the treatment period.
* The examination is particularly suitable for young persons in whom coronary heart disease is not suspected, and it should be used after consideration. In adult patients, exercise stress test or spiroergometry is usually performed when assessing respiratory or chest symptoms on exertion, whether the symptoms originate from the heart or lungs or the patient's working capacity.
Radiological examinations
  • Chest x-ray
    • Once initially as differential diagnostic examination (heart failure, lung tumour, infection) and after that at discretion during exacerbations or if treatment response is poor
  • Evaluation of the status of the sinuses and, as needed, sinus ultrasonography or x-ray
    • Sinusitis may be the cause of prolonged cough.
    • Sinusitis often is an underlying factor in exacerbations of asthma.

Allergy tests and blood tests

  • Asthma typing includes blood eosinophil count.
  • Allergy may be investigated by skin prick testing Diagnostic Tests in Dermatology or by determination of allergen-specific IgE antibodies in order to examine e.g. allergy to pollen or animals or when biological drug treatment is considered.

Exhaled nitric oxide (FeNO) Exhaled Nitric Oxide Levels to Guide Treatment for Adults with Asthma

  • Increased concentration of nitric oxide in the exhaled air (fractional exhaled nitric oxide, FeNO) is an indicator of eosinophilic inflammation.
    • Eosinophilic inflammation can also be evaluated by blood eosinophilic white blood cell count or by the concentration of eosinophils in a sputum sample.
  • In a number of persons with asthma the NO concentration is increased in comparison to healthy persons. Large concentrations are seen particularly in atopic asthma.
  • NO production in the airways may be increased in other atopic persons as well. This is considered to be a consequence of subclinical mucosal inflammation.
  • In a number of asthma patients the exhaled NO concentration measured before initiation of treatment correlates moderately to clinical indicators of asthma, e.g. symptoms.
  • The test does not substitute for investigations measuring bronchial dysfunction, is not sufficient to diagnose asthma without other investigations and is not useful in the follow-up of all asthma patients.

Differential diagnosis

References

Evidence Summaries ⬆