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Table 2 The model infit index, item difficulty parameters, and separation in the Symptom, Activity, and Impact domain of the SGRQ by the order of item difficulty

From: A psychometric assessment of the St. George’s respiratory questionnaire in patients with COPD using rasch model analysis

Domain/item

Infit index

Item difficulty (SE)

Reliability (separation index)

Symptoms domain

  

0.59 (1.21)

 S_a5. Very bad unpleasant attacks of chest troubleb

0.85

−1.09 (0.06)

 

 S_a4. Attacks of wheezing

0.87

−0.18 (0.06)

 

 S_a3. Shortness of breath

0.90

0.09 (0.05)

 

 S_a7. How many good days (with little chest trouble)

1.46a

0.23 (0.06)

 

 S_a1. Coughed

0.87

0.47 (0.06)

 

 S_a2. Brought up phlegm (sputum)

1.08

0.47 (0.06)

 

Activity domain

  

0.86 (2.50)

 A_c1. Sitting or lying still

1.40

−6.42 (0.46)

 

 A_c2. Getting washed or dressed

0.93

−3.53 (0.24)

 

 A_g1. Take a long time to get washed or dressed

1.08

−3.14 (0.23)

 

 A_g2. Cannot take a bath or shower, or take a long time

0.90

−2.84 (0.22)

 

 A_c3. Walking around the home

0.86

−2.56 (0.21)

 

 A_c4. Walking outside on the level

0.82

−1.39 (0.20)

 

 A_g3. I walk more slowly than other people, or I stop for rests

1.09

−0.67 (0.19)

 

 A_g4. Jobs such as housework take a long time, or I have to stop for rests

0.81

0.04 (0.19)

 

 A_c5. Walking up a flight of stairs

0.92

0.38 (0.20)

 

 A_g5. If walk up one flight of stairs, I have to go slowly or stop

0.78

0.61 (0.20)

 

 A_c7. Playing sports or games

1.42a

2.54 (0.24)

 

 A_g7. Walk up hills, carry things up stairs or play golf

0.80

2.71 (0.24)

 

 A_c6. Walking up hills

1.35

2.77 (0.24)

 

 A_g6. If hurry or walk fast, I have to stop or slow down

0.86

2.96 (0.25)

 

 A_g8. Carry heavy loads, jog or walk at 5 miles per hour or swim

0.69

4.07 (0.30)

 

 A_g9. Very heavy manual work, run, cycle, play competitive sports

0.86

4.46 (0.32)

 

Impact domain

  

0.81 (2.08)

 I_h5. Move far from my bed or chair

0.94

−1.87 (0.26)

 

 I_f2. I get embarrassed using my medication in public

1.13

−1.30 (0.22)

 

 I_f1. My medication does not help me very much

1.25

−1.30 (0.22)

 

 I_e5. I do not expect my chest to get any better

0.90

−0.91 (0.20)

 

 I_d3. I get breathless when I talk

0.76

−0.72 (0.19)

 

 I_d4. I get breathless when I bend over

0.84

−0.62 (0.19)

 

 I_h3. Go out of the house to do the shopping

0.88

−0.54 (0.18)

 

 I_f3. I have unpleasant side effects from my medication

1.17

−0.54 (0.18)

 

 I_f4. My medication interferes with my life a lot

1.07

−0.51 (0.18)

 

 I_h4 Do housework

0.87

−0.50 (0.18)

 

 I_d1. My cough hurts

0.87

−0.45 (0.18)

 

 I_e2. My chest trouble is a nuisance to my family, friends or neighbors

0.99

−0.35 (0.18)

 

 I_b2. Chest trouble affect my work

1.21

−0.20 (0.12)

 

 I_e3. I get afraid or panic when I cannot get my breath

0.96

−0.17 (0.17)

 

 I_i. Best describes how your chest affects youb

0.98

−0.13 (0.10)

 

 I_e4. I feel that I am not in control of my chest problem

0.89

−0.11 (0.17)

 

 I_h2. Go out for entertainment or recreation

0.80

0.15 (0.16)

 

 I_e1. My cough or breathing is embarrassing in public

1.16

0.24 (0.16)

 

 I_d2. My cough makes me tired

0.94

0.88 (0.15)

 

 I_d5. My cough or breathing disturbs my sleep

1.13

0.93 (0.15)

 

 I_h1. Play sports or games

0.88

1.11 (0.15)

 

 I_b1. How would you describe your chest condition

2.00a

1.15 (0.08)

 

 I_d6. I get exhausted easily

0.90

1.19 (0.15)

 

 I_e6. I have become frail or an invalid because of my chest

0.74

1.21 (0.15)

 

 I_e8. Everything seems too much of an effort

0.76

1.62 (0.15)

 

 I_e7. Exercise is not safe for me

0.89

1.75 (0.16)

 
  1. Estimates were obtained from a mixed rating scale and partial credit model by Winsteps
  2. aItem misfit (infit index > 1.4) bReversed item