Table 6.

Differential item functioning of the Romanian ThyPRO-39 questionnaire

Abbreviated items wording	Significance of DIF	Variance explained by DIF	Direction of DIF
Tiredness scale
Energetic*	<0.0001	10.9%	Romanian patients report being more energetic at low levels of tiredness and less energetic at high levels of tiredness; i.e. they have a more exaggerated response
Depressivity scale
Self confident*	<0.0001	3.4%	Romanian patients report being less self-confident at higher levels of expressivity
Emotional Susceptibility scale
In control	<0.0001	3.3%	Romanian patients report being less in control

^*Non-uniform DIF.