In order to properly interpret spirometric data one needs to know predicted values and their lower limits of normal. This software demonstrates the differences between predicted values, and how interpretation changes based on which predicted values are used.
There is increasing awareness that using a fixed ratio of 0.70 for the lower limit of the FEV1/FVC ratio leads to significant over-diagnosis of COPD in middle-aged and elderly subjects, and to under-diagnosis in younger adults. This is exacerbated by the use of a fixed 80%predicted lower limit for FEV1. The Pulmonaria Group have assembled overwhelming evidence to that effect which is described in this software and the help file
This software shows you graphically the Lower Limit of Normal according to regression equations from 72 published studies, leading to 78 regression equations for women and 80 for men, for different ethnic groups, and for FEV1%FVC, FVCand FEV1. There is also numeric display of these LLNs.
You can also enter spirometric data and inspect how they compare to the various predicted values.
In addition there are data from over 50,000 subjects: hospital patients (St. Louis, USA and Rotterdam, NL), the NHANES III population, the Lung Health Study for England 1995/1996, a study by Gore (AUS), and a longitudinal study of two Dutch populations. These data are used to visualize the false-positive and false-negative rates, the predictive value of negative and positive test results, in the various populations. All regression equations and their Lower Limits of Normal are documented in the extensive help file.
A full list of references to the literature is available here.
Download free software (3.8 MB, version 3.1.0.118) Latest update March 12, 2010