A Revisited View of the Paced Auditory Serial Addition Test (PASAT) in Multiple Sclerosis

To the Editor: The Paced Auditory Serial Addition Test (PASAT) has been used since 1974 as a common research tool for different neurological disorders like multiple sclerosis. 1 In multiple sclerosis clinics, the PASAT has been included as a major test to determine the multiple sclerosis outcome because of its sensitivity to multiple sclerosis-related cognitive decline. 2 PASAT is one of the major components of Multiple Sclerosis Functional Composite test. 3

In PASAT, patients are trained to add 60 pairs of single digits so that each number is added to the one immediately preceding it. Patients report the sum orally. The digits are presented by audiotape, first at a rate of 3 seconds per digit (PASAT3), then, in a second trial, at a rate of 2 seconds per digit (PASAT2). Scores are the sums of correct responses for the 3- and 2- second forms of the task. 3, 4

We hypothesize that paying attention to the time of correct response may be valuable. For instance, in PASAT3, instead of taking into account the trueness or falseness of response, we consider the time of the patient’s reply. If he or she replies correctly, we consider the time. If he or she replies falsely, we consider 3 seconds, and if he runs out of time, we consider 3 seconds. By this approach, we have a signal: x-axis stands for 60 events (60 pairs of digits), and the y-axis stands for the time of reply. The maximum of the x-axis is 60, with steps from 1 to 60, and the y-axis maximum is 3 seconds.

We believe that such a signal might give clinicians better insight into the cognitive status of multiple sclerosis patients. For instance, the mean or the standard deviation of this signal may suggest the mean attention or the degree of his or her disturbance. We think that this modified PASAT may help improve the Multiple Sclerosis Functional Composite test.