Asthma Management Handbook

Confirming the diagnosis of asthma in adults

Recommendations

Before starting preventer treatment, confirm the diagnosis of asthma if possible (unless symptoms are severe).

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):

  • Aaron et al. 20081
  • Lucas et al. 20082
  • Luks et al. 20103
  • Marklund et al. 19994

For patients who report the diagnosis of asthma made in the past or elsewhere, confirm the diagnosis if possible.

Table. Confirming the diagnosis of asthma in a person using preventer treatment Opens in a new window Please view and print this figure separately: https://www.asthmahandbook.org.au/table/show/9

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):

  • Aaron et al. 20081
  • Lucas et al. 20082
  • Luks et al. 20103
  • Marklund et al. 19994

For a patient with a diagnosis of asthma and new respiratory symptoms, confirm the symptoms are due to asthma.

How this recommendation was developed

Consensus

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

More information

Confirming the diagnosis of asthma in adults and adolescents

A prior diagnosis of asthma reported by a patient should be corroborated by documentation of how the diagnosis was confirmed at the time, or by current evidence.

Reports from around the world show that 25–35% of people with a diagnosis of asthma in primary care may not actually have asthma.2345 Wheezing and other respiratory symptoms do not always mean a person has asthma. Airflow limitation demonstrated on spirometry can be transient and does not necessarily mean that the person has asthma (e.g. when recorded during a severe acute viral infection of the respiratory tract). Ideally, airflow limitation should be confirmed when the patient does not have a respiratory tract infection.

Once a person is already taking regular treatment with a preventer, it may be more difficult to confirm the diagnosis because variability in lung function often decreases with treatment.

Table. Confirming the diagnosis of asthma in a person using preventer treatment Opens in a new window Please view and print this figure separately: https://www.asthmahandbook.org.au/table/show/9

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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.6 Normal FEV1/FVC values derived from population studies vary,78 but are usually greater than:7

  • 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.8

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.96 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.10,11

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References

  1. Aaron SD, Vandemheen KL, Boulet LP, et al. Overdiagnosis of asthma in obese and nonobese adults. CMAJ. 2008; 179: 1121-1131. Available from: http://www.cmaj.ca/content/179/11/1121.full
  2. Lucas AE, Smeenk FW, Smeele IJ, van Schayck CP. Overtreatment with inhaled corticosteroids and diagnostic problems in primary care patients, an exploratory study. Fam Pract. 2008; 25: 86-91. Available from: http://fampra.oxfordjournals.org/content/25/2/86.full
  3. Luks VP, Vandemheen KL, Aaron SD. Confirmation of asthma in an era of overdiagnosis. Eur Respir J. 2010; 36: 255-260. Available from: http://erj.ersjournals.com/content/36/2/255.full
  4. Marklund B, Tunsäter A, Bengtsson C. How often is the diagnosis bronchial asthma correct?. Fam Pract. 1999; 16: 112-116. Available from: http://fampra.oxfordjournals.org/content/16/2/112.full
  5. Aaron SD, Fergusson D, Dent R, et al. Effect of weight reduction on respiratory function and airway reactivity in obese women. Chest. 2004; 125: 2046-52. Available from: http://www.ncbi.nlm.nih.gov/pubmed/15189920
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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