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Table 3 Summary of key results from Rasch Analysis, classical psychometric testing, involvement of PPI representatives and discussions with the developers of CARIES-QC

From: Selection and validation of a classification system for a child-centred preference-based measure of oral health-related quality of life specific to dental caries

Item

Item Spread at Logit 0

Item level fit Chi Squared (P-value)

Differential Item Functioning (DIF)

Residual

SRM

Disordered thresholds

Missing Data (%)

Floor effects (%)

Ceiling effects (%)

Strong correlations with other items

Concerns from PPI reps

Concerns from CARIES-QC development

Hurt

1.605

5.142 (0.076)

✘

−0.757

0.61

✘

✓ (1.5)

✓ (17% ‘a lot’)

✓ (31% ‘not at all’)

✓ (annoy)

✘

✘

Hard to eat

1.585

1.288 (0.525)

✓ (agea and genderb)

0.048

0.30

✘

✓ (2)

✘

✓ (43% ‘not at all’)

✓ (carefully)

✘

✘

Eating on one side

0.858

0.868 (0.648)

✓ (ageb)

−0.793

0.33

✘

✓ (2.5)

✓ (25% ‘a lot’)

✓ (37% ‘not at all’)

✓ (annoy; carefully)

✓

✘

Food stuck

1.632

6.646 (0.036)

✓ (ethnicitya, b)

0.661

0.68

✘

✓ (2)

✓ (32% ‘a lot’)

✘

✘

✓

✓

Kept awake

1.202

0.612 (0.736)

✘

−0.393

0.39

✘

✓ (1.5)

✘

✓ (67% ‘not at all’)

✓ (annoy)

✘

✘

Feeling annoyed

1.174

8.699 (0.013)

✘

−1.802

0.93

✘

✓ (2)

✓ (18% ‘a lot’)

✓ (40% ‘not at all’)

✓ (hurt; one side; kept awake; carefully; cross)

✘

✘

Hurt when brushing

0.913

1.362 (0.506)

✓ (ethnicityb)

0.379

0.49

✘

✓ (0.5)

✘

✓ (57% ‘not at all’)

✘

✓

✘

Eat more carefully

1.019

4.367 (0.113)

✘

−1.801

0.38

✘

✘

✓ (18% ‘a lot’)

✓ (43% ‘not at all’)

✓ (hard to eat; one side; annoy; slowly)

✘

✘

Eat more slowly

0.988

1.775 (0.412)

✓(deprivationa)

−0.874

0.16

✘

✓ 0.5

✘

✓ (55% ‘not at all’)

✓ (carefully)

✓

✘

Feeling cross

0.705

2.368 (0.306)

✓ (agea and ethnicityb)

0.130

0.51

✘

✘

✘

✓ (59% ‘not at all’)

✓ (annoy)

✓

✘

Cried

1.466

4.237 (0.120)

✘

1.112

0.44

✘

✘

✘

✓ (38% ‘not at all’)

✘

✓

✘

Difficulty doing schoolwork

0.894

1.339 (0.512)

✓ (ethnicitya)

−0.536

0.09

✘

✓ (0.5)

✘

✓ (82% ‘not at all’)

✘

✓

✓

  1. DIF differential item functioning, SRM:standardised response mean aUniform DIF b Non-uniform DIF