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Table 7 Differential item functioning tested for gender

From: Psychometric properties of the Danish Hospital Anxiety and Depression Scale in patients with cardiac disease: results from the DenHeart survey

 

OR (95% CI)a

for item responses

1, 2 and 3

Overall

p-value

Significant interaction between gender and sub scale

Nagelkerke’s R2

Step 1

Nagelkerke’s R2

Step 2

Nagelkerke’s R2

Step 3

DIF R2 b

HADS-A

 Item 1. I feel tense or ‘wound up’

  

X

0.6712

0.6714

0.6717

0.0005

 Item 3. I get a sort of frightened feeling as if something awful is about to happen

1: 0.948 (0.782;1.149)

2: 0.801 (0.719;0.892)

3: 0.916 (0.820;1.023)

0.0007

 

0.6287

0.6293

0.6295

0.0008

 Item 5. Worrying thoughts go through my mind

  

X

0.6924

0.6930

0.6932

0.0008

 Item 7. I can sit at ease and feel relaxed

  

X

0.6008

0.6011

0.6018

0.0010

 Item 9. I get a sort of frightened feeling like ‘butterflies’ in the stomach

  

X

0.6718

0.6726

0.6730

0.0012

 Item 11. I feel restless as I have to be on the move

1:1.670 (1.315;2.122)

2: 1.385 (1.240;1.545)

3: 1.423 (1.289;1.571)

<.0001

 

0.4746

0.4785

0.4788

0.0042

 Item 13. I get sudden feelings of panic

1: 0.667 (0.462;0.963)

2: 0.712 (0.600;0.845)

3: 0.781 (0.703;0.868)

<.0001

 

0.6291

0.6307

0.6308

0.0017

HADS-D

 Item 2. I still enjoy the things I used to enjoy

  

X

0.6107

0.6112

0.6116

0.0009

 Item 4. I can laugh and see the funny side of things

1: 0.865 (0.587;1.274)

2: 0.917 (0.765;1.099)

3: 0.805 (0.719;0.902)

0.0025

 

0.5739

0.5747

0.5747

0.0008

Item 6. I feel cheerful

1: 1.079 (0.750;1.551)

2: 1.089 (0.937;1.266)

3: 1.071 (0.956;1.200)

0.5055

 

0.6381

0.6381

0.6385

0.0004

Item 8. I feel as if I am slowed down

  

X

0.5660

0.5676

0.5684

0.0024

Item 10. I have lost interest in my appearance

1: 0.813 (0.561;1.177)

2: 1.050 (0.905;1.218)

3: 0.956 (0.866;1.054)

0.3345

 

0.4235

0.4237

0.4239

0.0003

Item 12. I look forward with enjoyment to things

  

X

0.6136

0.6142

0.6143

0.0007

Item 14. I can enjoy a good book or radio or TV program

1: 2.132 (1.558;2.918)

2: 1.612 (1.361;1.909)

3: 1.431 (1.289;1.587)

<.0001

 

0.3805

0.3853

0.3855

0.0050

  1. a Partial proportional odds model with item response as dependent variable and gender and subscale as independent variable. Men are reference
  2. Step 1: Partial proportional odds model with item response as dependent variable including subscale
  3. Step 2: Partial proportional odds model with item response as dependent variable including subscale and gender
  4. Step 2: Partial proportional odds model with item response as dependent variable including subscale, gender and an interaction between the two
  5. b Indication of both uniform and non-uniform DIF
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