Defining normal

In tutorial 7, we explore how to define normal in spirometry, including reference equations that are used, the different methods to compare our patient to their normal, and the FEV1/FVC ratio and how this differs with age.

Key messages:

  • Defining normal in spirometry is not a straightforward as other diagnostic tests that we perform, and is affected by factors such as age, height, sex and ethnicity.
  • Reference equations are used to predict a patient’s normal, and once we have generated these predicted values we can begin by comparing the patient’s measured results with their predicted values.
  • In most major guidelines, the FEV1/FVC ratio is defined as abnormally reduced when it falls below 0.7, but we need to remember that the ratio declines with age, and so in some circumstances a patient might have abnormal test results according to the guidelines, but normal test results when compared to their normal population.

How to review and confirm the results are good quality

Patterns of abnormality

Mark as Understood

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