Perceived Deficits Questionnaire (PDQ)
The PDQ was developed by Sullivan et al, 1990 specifically for MS in order to provide a self-report measure of cognitive dysfunction. This instrument provides an assessment of several domains of cognitive functioning that are frequently affected in MS: attention, retrospective memory, prospective memory, and planning and organization. The full-length PDQ consists of 20 items while the abbreviated version has 5 items. The abbreviated version can be used if time is limited but the full-length version has the advantage of generating subscales. The PDQ is one of the components of the MSQLI.
Administration time is approximately 5-10 minutes for the full-length version and 2-3 minutes for the abbreviated version.
The PDQ is a structured, self-report questionnaire that the patient can generally complete with little or no intervention from an interviewer. However, patients with visual or upper extremity impairments may need to have the PDQ administered as an interview. Interviewers should be trained in basic interviewing skills and in the use of this instrument.
The total score for the PDQ is the sum of the scores for the 20 items. Individual subscale scores for attention/concentration, retrospective memory, prospective memory, and planning/organization can also be generated by calculating the sum of specific sets of items.
The PDQ is easy to administer and focuses on everyday situations in which cognitive dysfunction may play a role. As such it has high face validity for patients. The availability of the four subscales, attention/concentration, retrospective memory, prospective memory, and planning/organization may be useful to investigators interested in testing hypotheses concerning these different areas of function. However, the four subscales tend to correlate highly with one another, which limits their usefulness to some extent. Since the PDQ assesses cognitive dysfunction by means of self-report rather than objective neuropsychological testing PDQ scores need to be interpreted accordingly. There are often significant discrepancies between patient self-reports of cognitive dysfunction and actual test results.
The full-length version of the PDQ has a Cronbach's alpha of .93 while the short form has an alpha of .84. Correlation between the PDQ and objective neuropsychological testing is low suggesting that the PDQ is not measuring cognitive dysfunction per se but other factors related to the ways in which patients perceive their functioning.