Improving the quality and applicability of the Dutch scales of the Communication Profile for the Hearing Impaired using item response theory.
OBJECTIVE
The aim of this study was to improve the quality and applicability of the 6 Dutch scales of the Communication Profile for the Hearing Impaired (CPHI; Demorest & Erdman, 1986, 1987, 1988) using item response theory (IRT). IRT modeling can produce precise, valid, and relatively brief instruments, resulting in minimal response burden (Edelen & Reeve, 2006).


METHODS
We investigated (a) whether items fit to the graded response model (GRM; Samejima, 1969) using Stone and Zhang's (2003) procedure to test goodness of fit and (b) whether items showed differential item functioning (DIF) with the IRT log-likelihood ratio approach for 5 group variables: gender, age, living arrangement, use of hearing aids, and degree of hearing impairment. We investigated the magnitude of DIF by calculating the maximum difference between expected item scores for subgroups of the group variables of items showing DIF.


RESULTS
In a cross-sectional study, 408 consecutive individuals with hearing impairment completed the Dutch CPHI scales. Twelve items were deleted because of misfit to GRMs, 14 items showed uniform DIF, and 2 showed nonuniform DIF. Five items showing DIF were deleted due to large magnitude of DIF. The short form of the Dutch CPHI scales contains 35 items.


CONCLUSIONS
DIF analyses showed that the short form was relatively free of DIF with respect to the 5 group variables. Hence, there is no need to make adjustments for the calculation of subgroup scores.
EMGO Institute for Health and Care Research, VU University Medical Center, Van der Boechorststraat 7, 1081 BT, Amsterdam, the Netherlands. w.mokkink@vumc.nl
Lidwine B
LB
Mokkink
Dirk L
DL
Knol
Ruth M A
RM
van Nispen
Sophia E
SE
Kramer
D000223:Adaptation, Psychological; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003142:Communication; D003430:Cross-Sectional Studies; D005260:Female; D006310:Hearing Aids; D006311:Hearing Disorders / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D008960:Models, Psychological; D011336:Probability; D011795:Surveys and Questionnaires; D055815:Young Adult