Validity and reliability of the perceived deficit questionnaire to assess cognitive symptoms in people with chronic whiplash-associated disorders

Takasaki H, Chien C-W, Johnston V, Treleaven J, Jull G. Validity and reliability of the Perceived Deficit Questionnaire to assess cognitive symptoms in people with chronic whiplash-associated disorders. Objective: To investigate the validity and reliability of the Perceived Deficit Questionnaire (PDQ) for use in people with chronic whiplash-associated disorders. Design: Cross-sectional. Setting: Tertiary institution. Participants: Patients (N=105) with chronic whiplash-associated disorders and asymptomatic controls (n=50). Interventions: Not applicable. Main Outcome Measures: The 20-item PDQ inclusive of 4 sections (attention/concentration, retrospective memory, prospective memory, and organization/planning) rated on a 5-point scale. Results: Internal construct validity of the PDQ was examined by Rasch analysis, confirming the appropriateness of its 5-point scale and the unidimensionality of each section after modification by eliminating 1 item each from the attention/concentration and retrospective memory sections. Preliminary evidence was also gained for external construct validity (convergent validity) of the modified PDQ by demonstrating significant (P<.05) correlations of all sections with a global measure of disability due to neck pain (the Neck Disability Index). The whiplash group demonstrated significantly (P<.05) higher scores in each section of the modified PDQ than did the control group, indicating evidence for discriminant validity. In addition, the modified PDQ demonstrated good internal consistency (Rasch-generated reliability >.8) and acceptable test-retest reliability with 1-month interval (intraclass correlation coefficients >.8). Conclusions: The modified PDQ appears to be a valid and reliable questionnaire and could be used quickly in clinical practice to gain a basic understanding of perceived cognitive symptoms in people with chronic whiplash-associated disorders.