Gender bias in the sixteen-item Anxiety Sensitivity Index: an application of polytomous differential item functioning.

Gender differences in measures of anxiety sensitivity (AS) are similar to gender differences across anxiety disorders; females exhibit higher levels of AS and a greater prevalence of anxiety disorders than males. The current study confirms higher scores on the Anxiety Sensitivity Index (ASI) in females. Further analysis reveals, however, that gender differences on the ASI may arise from a single item's bias against women. Four different statistics examining differential item functioning (DIF) indicate that women are more likely to endorse the item, "It scares me when I feel faint", even if they score no higher on the ASI than males. Removing this biased item does not alter internal consistency of the scale, but eliminates the significant gender difference. The results suggest that differences on the ASI require careful interpretation as item bias may artificially inflate ASI scores in females.