Table 2 Score of each anchor item, the distribution of the items and the polychoric correlation of each item with NYHA classification

Do you usually have breathlessness or difficulty breathing? ("dyspnea")

   Yes, when walking on steep plane

0.57

   Yes, when walking on the horizontal plane

   Yes, even at rest

If yes, how long can you walk before you have to stop?

("distance")*

   0-100 metres

0.33

   101-500 metres

   501-2500 metres

If yes, after how many sets of stairs (10-15 steps) do you have to stop? ("stairs")*

   1 set

0.66

   2 sets

   3 or more sets

If yes, in your view, what level of effort induces breathlessness? ("effort")

   Great efforts

0.67

   Average efforts

   Small efforts

Raw score (0-8)

0.62