Table 2 Summary of Rasch analysis results for the physical and emotional functioning domains

Physical functioning domain (factor 1) (PHPQoL-9)

Item no.

Item

Measure

Error

Infit

Outfit

2

I’ve felt sleepy after getting up in the morning and it’s been hard to get going

0.01

0.14

1.36

1.29

26

I’ve been able to carry out my activities as normal

−0.89

0.15

1.02

1.29

27

I’ve restricted some leisure activities because of the symptoms of the illness

−1.04

0.16

1.21

1.14

24

I’ve had back pain

0.72

0.14

1.19

1.18

5

I’ve noticed that I get short of breath when I walk quickly

−0.33

0.15

1.18

1.06

25

My bones and/or joints have ached

1.15

0.015

1.18

1.06

28

The illness has limited what household chores I do

−0.74

0.15

1.02

0.90

4

I’ve found it difficult to walk for a long time

0.25

0.14

0.88

0.89

3

I’ve felt weak

0.15

0.14

0.62

0.65

Emotional functioning domain (factor 2) (PHPQoL-7)

Item no.

Item

Measure

Error

Infit

Outfit

17

I’ve found it hard to concentrate

−0.17

0.14

1.28

1.24

34

I’ve noticed I find it more difficult to concentrate at work than before

−0.73

0.16

1.19

1.04

12

I’ve slept well

−0.51

0.15

1.13

1.08

19

I’ve been worried, not only about the illness but also its complications

0.25

0.14

1.09

1.06

13

I’ve woken up during the night

0.80

0.14

0.85

0.90

8

I’ve felt depressed

0.15

0.14

0.84

0.83

7

I’ve been irritable

0.05

0.14

0.81

0.79