The FEV1/FVC ratio, also called 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 expiration. See the Wikipedia article on spirometry for the definitions of FEV1 and FVC.
Normal values are approximately 80%. Predicted normal values can be calculated online and depend on age, sex, height, weight 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.
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