* The cut-off values for the assignment of points are shown for each variable. The total possible values range from 0 to 10. FEV1%predicted denotes forced expiratory volume in one second as a percentage of the predicted value.
† The FEV1%predicted categories are based on stages identified by the American Thoracic Society.
‡ Scores on the modified Medical Research Council (MMRC) dyspnoea scale can range from 0 to 4; 0 – "Not troubled with breathlessness except with strenuous exercise"; 1 – "Troubled by shortness of breath when hurrying on the level or walking up a slight hill"; 2 – "Walks slower than people of the same age on the level because of breathlessness or has to stop for breath when walking at own pace on the level"; 3 – "Stops for breath after walking about 100 yards or after a few minutes on the level"; 4 – "Too breathless to leave the house or breathless when dressing or undressing"
§ The values for body-mass index were 0 or 1 because of the inflection point in the inverse relation between survival and body-mass index at a value of 21.