With 15 years of expertise in spirometry, Chris Loveridge answers your questions about spirometry and emphasises the need to take a clinical history.  

Chris Loveridge

Chris Loveridge

Read this Ask the expert article to learn more about the role of spirometry in diagnosing respiratory conditions.

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The subject of spirometry is a huge topic, despite the test itself being relatively simple to undertake. It is meaningless if it is done incorrectly and unfortunately, the resulting misdiagnosis is a cause for concern. 

In 2013, A guide to performing quality assured diagnostic spirometry was published. This guide was developed to address the concerns about misdiagnosis by establishing standards for a reliable and accurate spirometry method, and the equipment required to carry it out.1 Although the guide was published in 2013, it had been in development for years; a testament to the confusion and disagreement about spirometry and who should be performing it. Traditionally spirometry was in the domain of respiratory physiologists, and 15–20 years ago it was seen as something that should not be done in primary care. However, the tide is now turning and it is now more widely accepted, but generally unfunded, in primary care. This lack of funding has been an issue and when the competence document Improving the quality of diagnostic spirometry in adults: the National Register of certified professionals and operators was published there was concern that the need to be on a register to demonstrate competence was not associated with allocated funds for education and training.

The NHS long term plan has acknowledged that when managing respiratory conditions the biggest problem is accurate diagnosis. The plan states that this needs to be addressed and implies that there will potentially be funding to support this. This is welcome news to those of us evangelical about the need for accurate and safe spirometry. It is unforgivable that up to 50% of people in primary care have an incorrect diagnosis2 and are taking treatment they do not need, or worse still do not get the treatment they require.

The Spirometry National Register is held by the Association for Respiratory Technology and Physiology (ARTP) and has been in place for many years. Education for Health has been one of the main providers of training and accreditation since 2006 placing hundreds of people on the register. This year, the ARTP partnered with a different provider of training and assessment—the Institute of Clinical Science and Technology (ICST). This is now an online system with only one route to assessment. Any organisation or individual can provide training but the assessment is only via the ICST.

Clinical history should always underpin the diagnosis so taking a thorough, accurate clinical history is important. In my opinion, there is a risk associated with any change in system that this key skill, of taking an accurate clinical history, is overlooked in the need to get everyone on to the register. It is not mandatory to be on the register, as there is no policing mechanism, but it is an indication of clinical governance. Primary care consists of independent contractors (general practice) and even if there were concerns about the quality of practice, an individual cannot go in and remove the spirometer! We have to rely on the professional accountability of those undertaking the test (and interpreting it) and the recognition of their own competence.

In my position as spirometry lead at Education for Health, I travel around the UK teaching spirometry, and it is those who are unconsciously incompetent (e.g. the ones saying ‘I have been doing it for years and know all about it’) who learn the most. In my weekly clinics, I find myself telling patients ‘I am really pleased to tell you that you do not have COPD’, or conversely telling people that they have asthma and they should start taking their inhaled corticosteroid (ICS)!

Misdiagnosis of respiratory conditions must be addressed, and a step in the right direction is good quality training and education around diagnostic spirometry. The questions below for this Ask the expert article are examples of common scenarios encountered in general practice, and demonstrate the need for support and training for those diagnosing people with respiratory diseases.

  1. When undertaking spirometry with reversibility, how would you work out the percentage of reversibility on FEV1? I am a practice nurse and I have been getting different advice

Reversibility is a difficult area as the recommendations from BTS/SIGN, NICE asthma, and NICE COPD)4,5,6 all differ. The degree of reversibility is measured by the change in FEV1 before and after administration of a bronchodilator; significant reversibility suggests a diagnosis of asthma is more likely. In some guidelines, a specified increase in volume is quoted; for example, the NICE COPD guideline recommends ‘a large (over 400 ml) response to bronchodilators’ as a finding to help identify asthma.6 The percentage degree of reversibility varies from guideline to guideline and is based on very old research. Poor technique in the pre- bronchodilator test can give false values, as can poor reproducibility between blows. If we allow 150 ml between blows and then say reversibility is 200 ml, how can we be sure it is ‘true’ reversibility and not poor technique? This illustrates the importance of good quality spirometry in the diagnosis of respiratory conditions.

As with any guideline, the important thing is the patient in front of you and their clinical history. If a patient presents with atopy (hay fever, eczema, or rhinitis), night-time cough, and intermittent wheezing then it is classic asthma, almost irrespective of the reversibility. If they then demonstrated reversibility by 350 ml, would you say they had COPD because it was not 400 ml? You would not! Fundamentally, it is down to the patient’s individual clinical history over and above the degree of reversibility.

Also consider that only around 20–25% of smokers develop COPD,7 but a very high proportion of older people with chronic asthma will develop fixed airways disease through the lack of availability of steroids in previous years. Would you say that these people do not have COPD because they have never smoked, or have an insignificant smoking history?

The difficulty we have is that guidelines—and more recently, quality standards—ask for objective measures to ‘prove’ the diagnosis. As with any objective measures, there are grey areas because we are dealing with individuals. Any person whose symptoms improves with treatment and their lung function returns to normal or shows ‘significant’ improvement should be considered to have asthma if the history supports it. Anyone whose symptoms do not improve needs further investigation and a reconsideration of the history, including occupational exposure and other non-respiratory causes.

  1. Is testing for peak flow variability still useful?

Peak flow diaries and symptom diaries still have a place in the diagnosis of asthma.4 Baseline (pre-bronchodilator) spirometry in a person with suspected asthma may well be normal despite their symptoms and history suggesting they have asthma. Therefore, a trial of treatment (i.e. an ICS), accompanied by a peak flow and/or symptom diary can help ‘prove’ the diagnosis, as well as aid concordance with ICS treatment, as the person sees their symptoms improve and their variability in the peak flow lessen.

  1. A 58-year-old man presents with cough and sputum. He is a recent ex-smoker with a 30 year-pack history. His chest X-ray shows background COPD, and the spirometry meets the criteria and shows normal airflow with ratio above lower limit of normal (LLN). As this man still has cough with sputum with incidental finding of background COPD but normal spirometry results, how would you suggest that he is coded and managed?

The difficulty with the question posed is that there are gaps in the patient’s history. This emphasises the importance of taking a history when making a diagnosis, and the danger of the overreliance on spirometry to help you get an answer. Although 30 pack-years is a significant smoking history, only 20–25% of smokers develop COPD.7

Signs relating to cough and sputum need further questioning. When are they coughing? Does this happen at night time? Is it associated with food? Is the coughing affected by change of temperature or exercise? How much sputum is being produced? A teaspoon, tablespoon, egg cup, or tea cup? When is the sputum produced? What is the colour and consistency? In terms of the patient having a comfortable sleeping position and being able to breathe, how many pillows do they sleep with?

It is also worth considering a different diagnosis—could the cough be due to heart disease?

An X-ray should not be used to inform a diagnosis of COPD as the signs often reported, such as hyper inflated lungs or flattened diaphragm, are also seen in asthma. When you say that spirometry meets criteria this does not give much information—how long did the patient blow for? Was there any concavity in the flow-volume trace? If the ratio is above lower limit of normal then this implies normal lung function, so a spirometry test on its own is not significant unless the volumes are reduced. If he has normal lung function he cannot have COPD. The only exception to having normal lung function and COPD is emphysema, which would need confirmation via high-resolution computed tomography. However, emphysema is unlikely given the sputum production. I would suggest that it would be better to revisit the history and consider other diagnoses, perhaps bronchiectasis?


Diagnostic spirometry is a huge area of discussion and there is a recognised training need. The inclusion in the 10-year plan will drive the need for accredited training and greater understanding of the importance of this relatively simple test in the diagnostic process.

For any further queries or comments please feel free to contact the author at c.loveridge@educationforhealth.org


  1. Primary Care Commissioning. A guide to performing quality assured diagnostic spirometry. PCC, 2013. Available at: www.pcc-cic.org.uk/sites/default/files/articles/attachments/spirometry_e-guide_1-5-13_0.pdf
  2. NHS England. Improving the quality of diagnostic spirometry in adults: the National Register of certified professionals and operators. London: NHS England, 2013. Available at: www.pcc-cic.org.uk/sites/default/files/articles/attachments/improving_the_quality_of_diagnostic_spirometry_in_adults_the_national_register_of_certified_professionals_and_operators.pdf
  3. NHS England. The NHS long term plan. London: NHS England, 2019. Available at: www.longtermplan.nhs.uk/publication/nhs-long-term-plan/
  4. British Thoracic Society, Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. SIGN 153. BTS/SIGN, 2016. Available at: www.brit-thoracic.org.uk/standards-of-care/guidelines/btssign-british-guideline-on-the-management-of-asthma/
  5. NICE. Asthma: diagnosis, monitoring and chronic asthma management. NICE Guideline 80. NICE, 2017. Available at: www.nice.org.uk/NG80
  6. NICE. Chronic obstructive pulmonary disease in over 16s: diagnosis and management. NICE Guideline 115. NICE, 2017. Available at: www.nice.org.uk/NG115
  7. Løkke A, Lange P, Scharling H et al. Developing COPD: a 25 year follow up study of the general population. Thorax 2006; 61 (11): 935–939.