Before revision:  Cultural, age and gender bias were assessed on item level using differential item functioning (DIF) and on scale level by calculating correlations between IADL and cognitive and functional measures . RESULTS: We did not find meaningful bias on item or on scale level, as indicated by low DIF effect sizes (  R2 range 0-0.03) and correlations in expected directions and of similar magnitude. DISCUSSION: Our results suggest that IADL may be universally suitable as outcome measure. The A-IADL-Q seems robust to demographic diversity and is capable of reliably measuring IADL impairment .
After revision:  Cultural, age and gender bias were assessed on item level using differential item functioning (DIF) and on scale level by calculating correlations between IADL and cognitive and functional measures . RESULTS: We did not find meaningful bias on item or on scale level, as indicated by low DIF effect sizes ( R2 range 0-0.03) . Impact on total scores was minimal. DISCUSSION: The results imply a limited bias for age, gender, education and culture in the measurement of functional impairment. This study provides an important step in recognizing the potential influence of diversity on primary outcomes in dementia research .