Researchers studying the health of migrants frequently use standard quantitative instruments to
assess psychological constructs. Such instruments are often validated only in the respective
source population of migrants. For example when studying Turkish migrants in Germany
instruments validated in Turkey are applied. However considerable differences in culture and
language may have developed between migrants and their source population. These differences
limit the validity and reliability of quantitative instruments a problem that is often
overlooked. Using the example of the Revised Illness Perception Questionnaire (IPQ-R) the
authors demonstrate that instruments known to be valid and reliable in source populations may
lead to biased results when applied to migrant populations.
