The FEV1/FVC ratio is a calculated ratio used in the diagnosis of obstructive and restrictive lung disease.[1][2]
It represents the proportion of the forced vital capacity exhaled in the first second[3].
Normal values are approximately 80%.[
Disease states
In obstructive lung disease, the FEV1 is reduced due to obstruction to air escape. Thus, the FEV1/FVC ratio will be reduced[5]. More specifically, the diagnosis of COPD is made when the FEV1/FVC ratio is <70%.[6] The GOLD criteria also requires that values are after bronchodilator medication has been given to make the diagnosis, and the NICE criteria also requires FEV1% to be <80% id="cite_ref-Nathell_5-1" class="reference" style="line-height: 1em; font-weight: normal; font-style: normal; ">[6] According to the ERS criteria, it is FEV1% predicted that defines when a patient has COPD, that is, when FEV1% predicted is < id="cite_ref-Nathell_5-2" class="reference" style="line-height: 1em; font-weight: normal; font-style: normal; ">[6]
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 norma
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