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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. [4] More specifically, according to the National Institute for Clinical Excellence, the diagnosis of COPD is made when the FEV 1 /FVC ratio is less than 0.7 or [8] the FEV 1 is less than 75% of predicted; [9] however, other authoritative bodies have ...
English: Normal values for Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 Second (FEV1) and Forced Expiratory Flow 25–75% (FEF25–75%). Y-axis is expressed in Litres for FVC and FEV1, and in Litres/second for FEF25–75%. See main article: Wikipedia:Spirometry
FEV1 is the volume of air that can forcibly be blown out in first 1-second, after full inspiration. [13] Average values for FEV1 in healthy people depend mainly on sex and age, according to the diagram. Values of between 80% and 120% of the average value are considered normal. [14]
English: Normal values for Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 Second (FEV1) and Forced Expiratory Flow 25–75% (FEF25–75%). Y-axis is expressed in Litres for FVC and FEV1, and in Litres/second for FEF25–75%.
In obstructive lung disease however, the FEV1/FVC is less than 0.7, indicating that FEV1 is significantly reduced when compared to the total expired volume. This indicates that the FVC is also reduced, but not by the same ratio as FEV1. [8] One definition requires a total lung capacity which is 80% or less of the expected value. [9]
An increase in FEV1 (or forced expiratory volume in the first second of a forced exhalation) of >200ml is considered a positive result. Bear in mind, however, that this number does not apply to children, and that it can differ depending on the patient's native result; small patient's with pulmonary fibrosis , restrictive lung disease etc. will ...
The positive predictive value (PPV), or precision, is defined as = + = where a "true positive" is the event that the test makes a positive prediction, and the subject has a positive result under the gold standard, and a "false positive" is the event that the test makes a positive prediction, and the subject has a negative result under the gold standard.
Pre-exposure prophylaxis (PrEP), is the use of medications to prevent the spread of disease in people who have not yet been exposed to a disease-causing agent. Vaccination is the most commonly used form of pre-exposure prophylaxis ; other forms of pre-exposure prophylaxis generally involve drug treatment, known as chemoprophylaxis .