Evaluation of candidate symptoms for PGD (<i>n</i> = 287).

Relatively uninformative (Imax<0.20) or biased symptoms are displayed in bold font. All others are informative, unbiased symptoms and were retained for further analysis. aIRT IIF analysis was performed using all 22 symptoms, showing 16 to be informative (Imax≥0.20). bIRT DIF analysis was restricted to 16 relatively informative symptoms, showing four to be biased. cImax represents maximum item information relative to that of “inability to care about others….” dΘmax represents location of Imax for the item along the PG attribute scale.