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FEV1/FVC ratio

Ratio used in the diagnosis of lung disease

Ratio used in the diagnosis of lung disease

The FEV1/FVC ratio, also called modified Tiffeneau-Pinelli index, is a calculated ratio used in the diagnosis of obstructive and restrictive lung disease. It represents the proportion of a person's vital capacity that they are able to expire in the first second of forced expiration (FEV1) to the full, forced vital capacity (FVC). FEV1/FVC ratio was first proposed by E.A. Haensler in 1950. The FEV1/FVC index should not be confused with the FEV1/VC index (Tiffeneau-Pinelli index) as they are different, although both are intended for diagnosing airway obstruction. Current recommendations for diagnosing pulmonary function recommend using the modified Tiffeneau-Pinelli index (also known as the Haensler index). This index is recommended to be represented as a decimal fraction with two digits after the decimal point (for example, 0.70).

Normal values are approximately 75%. Predicted normal values can be calculated online and depend on age, sex, height, and ethnicity as well as the research study that they are based upon.

A derived value of FEV1% is FEV1% predicted, which is defined as FEV1% of the patient divided by the average FEV1% in the population for any person of similar age, sex, and body composition.

Disease states

In obstructive lung disease, the FEV1 is reduced due to an obstruction of air escaping from the lungs. Thus, the FEV1/FVC ratio will be reduced. More specifically, according to the National Institute for Clinical Excellence, the diagnosis of COPD is made when the FEV1/FVC ratio is less than 0.7 or the FEV1 is less than 75% of predicted; however, other authoritative bodies have different diagnostic cutoff points.

In restrictive lung disease, the FEV1 and FVC are equally reduced due to fibrosis or other lung pathology (not obstructive pathology). Thus, the FEV1/FVC ratio should be approximately normal, or even increased due to a decrease in magnitude of FVC as compared to FEV1 (because of the decreased compliance associated with the presence of fibrosis in some pathological conditions).

References

References

  1. Minelli R. Appunti dalle lezioni di fisiologia umana. La Goliardica Pavese, Pavia, 1992.
  2. (2008). "Using the lower limit of normal for the FEV1/FVC ratio reduces the misclassification of airway obstruction". Thorax.
  3. (1996). "Pulmonary function in obese subjects with a normal FEV1/FVC ratio". Chest.
  4. [http://www.gp-training.net/protocol/respiratory/copd/spirometry.htm Interpreting spirometry] {{Webarchive. link. (2008-07-25 . gp-training.net)
  5. Petty, Thomas L.. "The history of COPD".
  6. [https://jctm.mums.ac.ir/article_5843_216d82c71e95ae633457a44b6bf17583.pdf Mirsadraee M, Salarifar E, Attaran D. Evaluation of Superiority of FEV1/VC Over FEV1/FVC for Classification of Pulmonary Disorders. J Cardiothorac Med. 2015; 3(4):355-359.] {{Webarchive. link. (2017-11-16)
  7. "Forced Expiration". Johns Hopkins University.
  8. [http://www.nice.org.uk/guidance/CG101 Chronic obstructive pulmonary disease: Management of chronic obstructive pulmonary disease in adults in primary and secondary care (partial update)]. NICE.org.uk. June 2010
  9. [http://www.nice.org.uk/guidance/CG101 Chronic obstructive pulmonary disease: Management of chronic obstructive pulmonary disease in adults in primary and secondary care (partial update)]. NICE.org.uk. June 2010
  10. (2007). "COPD diagnosis related to different guidelines and spirometry techniques". Respiratory Research.
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