Cross-cultural validation of the German and Turkish versions of the PHQ-9: an IRT approach

BMC Psychology

Table 3 Analyses of differential item functioning (DIF)

	DIF related to language^a			DIF related to ethnicity and migration background^b
Item	Total^c	Slope parameter^d	Location parameters^e	Total^c	Slope parameter^d	Location parameters^e
1. Anhedonia	10.9*	6.4*	4.5	2.2	0.4	1.8
2. Depressed mood	4.3	0.5	3.8	4.0	0.3	3.7
3. Sleep problems	8.3	0.1	8.3*	5.3	0.4	4.9
4. Low energy	11.2*	0.0	11.2*	2.8	0.1	2.7
5. Appetite changes	19.7***	3.3	16.4***	14.8**	0.3	14.5**
6. Low self-esteem	3.6	0.3	3.3	0.2	0.0	0.2
7. Concentration difficulties	5.1	0.2	4.8	18.7***	6.8**	12.0**
8. Psychomotor changes	4.2	0.0	4.2	1.9	0.1	1.9
9. Suicidal ideation	5.6	0.4	4.2	3.0	0.3	2.7

We report X² statistics. Significant X² tests indicate that there is a difference in item functioning. Results for anchor items are printed in italics. X² values for anchor items are reported from the last iteration of step one, where anchor items have been selected and purified. Candidate for DIF items are in bold, and X² values are those estimated from the second stage of analysis, i.e. where candidate DIF items were tested against the previously identified set of DIF-free anchor items
^aAnalysis 1 comparing T-G (Turkish immigrants completing the German version of the PHQ-9, n = 191) with T-T (Turkish immigrants completing the Turkish version of the PHQ-9, n = 116). ^bAnalysis 2 comparing G-G (Germans with no migration background completing the German version of the PHQ-9, n = 1670) with T-G (Turkish immigrants completing the German version of the PHQ-9, n = 191). ^cdf = 4. ^ddf = 1. ^edf = 3
*p < .05, **p < .01, ***p < .001

ISSN: 2050-7283