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Table 3 Item Response Theory Properties, Factor Loadings, and Cronbach’s alpha of Patient Health Questionnaire 9-item (PHQ-9) and Patient Health Questionnaire 2-item (PHQ-2) Screening tools Administered in Primary Care Settings in Sofala, Mozambique

From: Validity and item response theory properties of the Patient Health Questionnaire-9 for primary care depression screening in Mozambique (PHQ-9-MZ)

Item

IRT Parameters

Factor loadings

Uniqueness

Item test correlation

Item rest correlation

Average interitem covariance

Item Cronbach’s Alpha

α

b1

b2

b3

PHQ1: Interest

2.00

−0.04

1.94

2.41

0.722

0.479

0.719

0.619

0.177

0.814

PHQ2: Hopeless

1.78

0.25

2.26

2.57

0.717

0.486

0.690

0.583

0.181

0.818

PHQ3: Sleep

1.40

0.12

1.94

2.25

0.582

0.661

0.620

0.466

0.182

0.835

PHQ4: Tired

1.83

−0.31

1.93

2.17

0.701

0.508

0.720

0.611

0.174

0.815

PHQ5: Appetite

1.29

0.40

2.25

2.69

0.564

0.682

0.629

0.490

0.183

0.830

PHQ6: Failure

1.78

1.53

N/R

2.71

0.747

0.443

0.651

0.558

0.191

0.822

PHQ7: Concentrating

1.74

0.56

2.31

2.51

0.728

0.469

0.712

0.610

0.178

0.815

PHQ8: Moving

2.08

0.60

2.32

2.57

0.753

0.433

0.718

0.627

0.181

0.814

PHQ9: Suicidal ideation

1.63

2.0

N/R

3.44

0.737

0.457

0.535

0.456

0.209

0.833

Overall PHQ-9

        

0.184

0.839

Overall PHQ-2

         

0.606

  1. Abbreviations: IRT Item Response Theory, N/R No responses at this level; α = item discrimination; b1 refers to endorsing “several days”, Portuguese: “Algumas vezes”; b2 refers to endorsing “more than half the days”, Portuguese: “