Description
The PASAT is a measure of cognitive function that assesses auditory information processing speed and flexibility, as well as calculation ability. It was developed by Gronwell in 1977 and later adapted by Rao and colleagues in 1989 for use in MS. The PASAT is presented using audio cassette tape or compact disk to ensure standardization in the rate of stimulus presentation. Single digits are presented every 3 seconds and the patient must add each new digit to the one immediately prior to it. Shorter inter-stimulus intervals, e.g., 2 seconds or less have also been used with the PASAT but tend to increase the difficulty of the task. Two alternate forms have been developed to minimize possible familiarity with the stimulus items when the PASAT is repeated over more than one occasion. The PASAT is the third and last component of the MSFC to be administered at each visit.

Administration Time
Administration time is approximately 10-15 minutes including practice sessions.

Administration Method
The PASAT is administered in person by a trained examiner. Among the three MSFC components, the PASAT probably requires the most training for examiners since subtle changes in the administration procedures can have a significant effect on the outcome.

Scoring
The score for the PASAT is the total number correct out of 60 possible answers. This score can be used individually or used as part of the MSFC composite score. See the MSFC Administration and Scoring Manual for details.

General Comments
The PASAT is a sensitive test of some specific cognitive functions frequently affected in MS. However, it is not intended to be a global measure of cognitive dysfunction. It is probably most useful for assessing mild to moderate dysfunction but less useful when cognitive deficits are severe.

Psychometric Properties
The PASAT has demonstrated high split-half reliability and evidence for convergent and divergent validity with good sensitivity for deficits in the areas of auditory information processing speed and flexibility. Performance on the PASAT is sensitive to practice effects, that is, patients often display poorer performance when first tested due to lack of familiarity with the task. It is recommended that three or four administrations be given prior to a baseline assessment if accurate (rather than comparative) assessments of change over time are needed.