Asthma Management Handbook

Making a diagnosis of asthma in adults

Recommendations

Consider features that increase or decrease the probability of asthma.

Table. Findings that increase or decrease the probability of asthma in adults

Asthma is more likely to explain the symptoms if any of these apply

Asthma is less likely to explain the symptoms if any of these apply

More than one of these symptoms:

  • wheeze
  • breathlessness
  • chest tightness
  • cough

Symptoms recurrent or seasonal

Symptoms worse at night or in the early morning

History of allergies (e.g. allergic rhinitis, atopic dermatitis)

Symptoms obviously triggered by exercise, cold air, irritants, medicines (e.g. aspirin or beta blockers), allergies, viral infections, laughter

Family history of asthma or allergies

Symptoms began in childhood

Widespread wheeze audible on chest auscultation

FEV1 or PEF lower than predicted, without other explanation

Eosinophilia or raised blood IgE level, without other explanation

Symptoms rapidly relieved by a SABA bronchodilator

Dizziness, light-headedness, peripheral tingling

Isolated cough with no other respiratory symptoms

Chronic sputum production

No abnormalities on physical examination of chest when symptomatic (over several visits)

Change in voice

Symptoms only present during upper respiratory tract infections

Heavy smoker (now or in past)

Cardiovascular disease

Normal spirometry or PEF when symptomatic (despite repeated tests)

Adapted from:

Respiratory Expert Group, Therapeutic Guidelines Limited. Therapeutic Guidelines: Respiratory, Version 4. Therapeutic Guidelines Limited, Melbourne, 2009.

British Thoracic Society (BTS) Scottish Intercollegiate Guidelines Network (SIGN). British Guideline on the Management of Asthma. A national clinical guideline. BTS/SIGN, Edinburgh; 2012. Available from: https://www.brit-thoracic.org.uk/guidelines-and-quality-standards/asthma-guideline/.

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How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to the following source(s):

  • Respiratory Expert Group, Therapeutic Guidelines Limited, 2009 1
  • British Thoracic Society, 2012 2

Make a diagnosis of asthma if all of the following apply:

  • The person has a history of variable symptoms (especially cough, chest tightness, wheeze and shortness of breath).
  • Expiratory airflow limitation has been demonstrated (FEV1/FVC less than lower limit of normal for age).
  • Expiratory airflow limitation has been shown to be variable.
  • There are no findings that suggest an alternative diagnosis.

Note: If the spirometer does not provide lower limit of normal for age, use the follow age-based cut-points to indicate expiratory airflow limitation in adults and older adolescents:

  • less than 0.85 (up to 19 years)
  • less than 0.80 (20–39 years)
  • less than 0.75 (40–59 years)
  • less than 0.70 (60 years and older).
How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

If a patient’s asthma has been diagnosed elsewhere (e.g. in a new patient reporting the diagnosis of asthma), try to confirm the diagnosis – whether or not the person has current symptoms, and whether or not the person is taking asthma medicines.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

More information

Definition of variable expiratory airflow limitation

Most of the tests for variable expiratory airflow limitation are based on showing variability in FEV1. While reduced FEV1 may be seen with many other lung diseases (or due to poor spirometric technique), a reduced ratio of FEV1 to FVC indicates airflow limitation.3 Normal FEV1/FVC values derived from population studies vary,45 but are usually greater than:4

  • 0.85 in people aged up to 19 years
  • 0.80 in people aged 20–39 years
  • 0.75 in people aged 40–59 years
  • 0.70 in people aged 60–80 years.

In children, it is less useful to define expiratory airflow limitation according to a specific cut-off for FEV1/FVC ratio, because normal values in children change considerably with age.5

Some spirometers provide predicted normal values specific to age group. If these are available, a FEV1/FVC ratio less than the lower limit of normal (i.e. less than the 5th percentile of normal population) indicates airflow limitation.

Variable expiratory airflow limitation (beyond the range seen in healthy populations) can be documented if any of the following are recorded:

  • a clinically important increase in FEV1 (change in FEV1 of at least 200 mL and 12% from baseline for adults, or at least 12% from baseline for children) 10–15 minutes after administration of bronchodilator
  • clinically important variation in lung function (at least 20% change in FEV1) when measured repeatedly over time (e.g. spirometry on separate visits)
  • a clinically important reduction in lung function (decrease in FEV1 of at least 200 mL and 12% from baseline on spirometry, or decrease in peak expiratory flow rate by at least 20%) after exercise (formal laboratory-based exercise challenge testing uses different criteria for exercise-induced bronchoconstriction)
  • a clinically important increase in lung function (at least 200 mL and 12% from baseline) after a trial of 4 or more weeks of treatment with an inhaled corticosteroid
  • clinically important variation in peak expiratory flow (diurnal variability of more than 10%)
  • a clinically important reduction in lung function (15–20%, depending on the test) during a test for airway hyperresponsiveness (exercise challenge test or bronchial provocation test) measured by a respiratory function laboratory.

Notes

Patients referred to a respiratory function laboratory may be asked not to take certain medicines within a few hours to days before a spirometry visit.

A clinically important increase or decrease in lung function is defined as a change in FEV1 of at least 200 mL and 12% from baseline for adults, or at least 12% from baseline for children, or a change in peak expiratory flow rate of at least 20% on the same meter.63 A clinically important increase in FVC after administering bronchodilator may also indicate reversible airflow limitation, but FVC is a less reliable measure in primary care because FVC may vary due to factors such as variation in inspiratory volume or expiratory time.

The finding of ‘normal’ lung function during symptoms reduces the probability that a patient has asthma, but a clinically important improvement in response to bronchodilator or inhaled corticosteroid can occur in patients whose baseline value is within the predicted normal range.

The greater the variation in lung function, the more certain is the diagnosis of asthma. However, people with longstanding asthma may develop fixed airflow limitation.

Reversibility in airflow limitation may not be detected if the person is already taking a long-acting beta2 agonist or inhaled corticosteroid.

Airflow limitation can be transient and does not necessarily mean that the person has asthma (e.g. when recorded during a severe acute infection of the respiratory tract). Ideally, airflow limitation should be confirmed when the patient does not have a respiratory tract infection. Reduction in lung function during a respiratory tract infection with improvement in lung function after its resolution, commonly occurs in people with asthma, but can also be seen in patients with COPD or in healthy people without either asthma or COPD.7,8

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Spirometry in diagnosis and monitoring

Spirometry is the best lung function test for diagnosing asthma and for measuring lung function when assessing asthma control. Spirometry can:

  • detect airflow limitation
  • measure the degree of airflow limitation compared with predicted normal airflow (or with personal best)
  • demonstrate whether airflow limitation is reversible.

It should be performed by well-trained operators with well-maintained and calibrated equipment.9, 6

Before performing spirometry, check if the person has any contraindications (e.g. myocardial infarction, angina, aneurysm, recent surgery, suspected pulmonary embolism, suspected pneumothorax, fractured ribs). Advise them to stop if they become dizzy.

Clearly explain and physically demonstrate correct spirometry technique: 10

  • Sit upright with legs uncrossed and feet flat on the floor and do not lean forward.
  • Breathe in rapidly until lungs feel absolutely full. (Coaching is essential to do this properly.)
  • Do not pause for more than 1 second.
  • Place mouthpiece in mouth and close lips to form a tight seal.
  • Blast air out as hard and fast as possible and for as long as possible, until the lungs are completely empty or you are unable to blow out any longer.
  • Remove mouthpiece.

Repeat the test until you obtain three acceptable tests and these meet repeatability criteria.

Acceptability of test

A test is acceptable if all the following apply:

  • forced expiration started immediately after full inspiration
  • expiration started rapidly
  • maximal expiratory effort was maintained throughout the test, with no stops
  • the patient did not cough during the test
  • the patient did not stop early (before 6 seconds for adults and children over 10 years, or before 3 seconds for children under 10 years).

Record the highest FEV1 and FVC result from the three acceptable tests, even if they come from separate blows.10

Repeatability criteria

Repeatability criteria for a set of acceptable tests are met if both of the following apply:9

  • the difference between the highest and second-highest values for FEV1 is less than 150 mL
  • the difference between the highest and second-highest values for FVC is less than 150 mL.

For most people, it is not practical to make more than eight attempts to meet acceptability and repeatability criteria.10

Testing bronchodilator response (reversibility of airflow limitation)

Repeat spirometry 10-15 minutes after giving 4 separate puffs of salbutamol (100 mcg/actuation) via a pressurised metered-dose inhaler and spacer.10 (For patients who have reported unacceptable side-effects with 400 mcg, 2 puffs can be used.)

For adults and adolescents, record a clinically important bronchodilator response if FEV1 increases by ≥ 200 mL and ≥ 12%.10

For children, record a clinically important bronchodilator response if FEV1 increases by
≥ 12%.10

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Making the clinical diagnosis of asthma in adults and adolescents

The clinical diagnosis of asthma is based on the probability that the symptoms are due to asthma rather than another cause, and on the magnitude of deviation from the level of lung function and the variation in lung function that is seen in a healthy population (i.e. demonstrating variable airflow limitation).

Table. Findings that increase or decrease the probability of asthma in adults

Asthma is more likely to explain the symptoms if any of these apply

Asthma is less likely to explain the symptoms if any of these apply

More than one of these symptoms:

  • wheeze
  • breathlessness
  • chest tightness
  • cough

Symptoms recurrent or seasonal

Symptoms worse at night or in the early morning

History of allergies (e.g. allergic rhinitis, atopic dermatitis)

Symptoms obviously triggered by exercise, cold air, irritants, medicines (e.g. aspirin or beta blockers), allergies, viral infections, laughter

Family history of asthma or allergies

Symptoms began in childhood

Widespread wheeze audible on chest auscultation

FEV1 or PEF lower than predicted, without other explanation

Eosinophilia or raised blood IgE level, without other explanation

Symptoms rapidly relieved by a SABA bronchodilator

Dizziness, light-headedness, peripheral tingling

Isolated cough with no other respiratory symptoms

Chronic sputum production

No abnormalities on physical examination of chest when symptomatic (over several visits)

Change in voice

Symptoms only present during upper respiratory tract infections

Heavy smoker (now or in past)

Cardiovascular disease

Normal spirometry or PEF when symptomatic (despite repeated tests)

Adapted from:

Respiratory Expert Group, Therapeutic Guidelines Limited. Therapeutic Guidelines: Respiratory, Version 4. Therapeutic Guidelines Limited, Melbourne, 2009.

British Thoracic Society (BTS) Scottish Intercollegiate Guidelines Network (SIGN). British Guideline on the Management of Asthma. A national clinical guideline. BTS/SIGN, Edinburgh; 2012. Available from: https://www.brit-thoracic.org.uk/guidelines-and-quality-standards/asthma-guideline/.

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Although untreated asthma is usually characterised by airway hyperresponsiveness and airway inflammation (eosinophilic and/or neutrophilic), these features are not essential for making the diagnosis of asthma in clinical practice.

The evidence for asthma must be documented at the time of diagnosis, because characteristic clinical, physiological and pathological features may improve spontaneously or with treatment, and because fixed (irreversible or incompletely reversible) airflow limitation may develop over time. It is often difficult to confirm the diagnosis of asthma after a patient has been started on preventer treatment.

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References

  1. Respiratory Expert Group, Therapeutic Guidelines Limited. Therapeutic Guidelines: Respiratory, Version 4. Therapeutic Guidelines Limited, West Melbourne, 2009.
  2. British Thoracic Society (BTS), Scottish Intercollegiate Guidelines Network (SIGN). British Guideline on the Management of Asthma. A national clinical guideline. BTS, SIGN, Edinburgh, 2012. Available from: https://www.brit-thoracic.org.uk/guidelines-and-quality-standards/asthma-guideline/
  3. Pellegrino R, Viegi G, Brusasco V, et al. Interpretative strategies for lung function tests. Eur Respir J. 2005; 26: 948-968. Available from: http://erj.ersjournals.com/content/26/5/948
  4. National Heart Lung and Blood Institute (NHLBI) National Asthma Education and Prevention Program. Expert Panel Report 3: guidelines for the diagnosis and management of asthma. Full report 2007. US Department of Health and Human Services National Institutes of Health, Bethesda, 2007. Available from: http://www.nhlbi.nih.gov/health-pro/guidelines/current/asthma-guidelines/full-report
  5. Quanjer PH, Stanojevic S, Cole TJ, et al. Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations. Eur Respir J. 2012; 40: 1324-43. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22743675
  6. Levy ML, Quanjer PH, Booker R, et al. Diagnostic Spirometry in Primary Care: Proposed standards for general practice compliant with American Thoracic Society and European Respiratory Society recommendations. Prim Care Respir J. 2009; 18: 130-147. Available from: http://www.ncbi.nlm.nih.gov/pubmed/19684995
  7. Collier AM, Pimmel RL, Hasselblad V, et al. Spirometric changes in normal children with upper respiratory infections. Am Rev Respir Dis. 1978; 117: 47-53. Available from: http://www.ncbi.nlm.nih.gov/pubmed/619724
  8. Melbye H, Kongerud J, Vorland L. Reversible airflow limitation in adults with respiratory infection. Eur Respir J. 1994; 7: 1239-1245. Available from: http://www.ncbi.nlm.nih.gov/pubmed/7925901
  9. Miller MR, Hankinson J, Brusasco V, et al. Standardisation of spirometry. Eur Respir J. 2005; 26: 319-338. Available from: http://erj.ersjournals.com/content/26/2/319
  10. Johns DP, Pierce R. Pocket guide to spirometry. 3rd edn. McGraw Hill, North Ryde, 2011.