Application of item response theory to achieve cross-cultural comparability of occupational stress measurement.

Our objective was to examine cross-cultural comparability of standard scales of the Effort-Reward Imbalance occupational stress scales by item response theory (IRT) analyses. Data were from 20,256 Japanese employees, 1464 Dutch nurses and nurses' aides, 2128 representative employees from post-communist countries, 963 Swedish representative employees, 421 Chinese female employees, 10,175 employees of the French national gas and electric company and 734 Spanish railroad employees, sanitary personnel and telephone operators. The IRT likelihood ratio model was used for differential item functioning (DIF) and differential test functioning (DTF) analyses. Despite the existence of DIF, most comparisons did not show discernible differences in the relations between Effort-Reward total score and level of the underlying trait across cultural groups. In the case that DTF was suspected, excluding an item with significant DIF improved the comparability. The full cross-cultural comparability of Effort-Reward Imbalance scores can be achieved with the help of IRT analysis.