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The MSIS-29 is a 29-item self-report measure with 20 items associated with a physical scale and 9 items with a psychological scale. Items ask about the impact of MS on day-to-day life in the past two weeks. All items have 5 response options: 1 “not at all” to 5”extremely”. Each of the two scales are scored by summing the responses across items, then converting to a 0-100 scale where 100 indicates greater impact of disease on daily function (worse health).

The physical impact score is computed by summing items number 1-20 inclusive. This score can then be transformed to a score on a scale of 0 -100 using the formula below:

(100*(observed score-20))
(100-20)

The psychological impact score is computed by summing items number 21-29 inclusive. This score can then be transformed to a score on a scale of 0 -100 using the formula below:

(100*(observed score-9))
(45-9)

For respondents with missing data, but where at least 50% of the items in a scale have been completed, a respondent–specific mean score computed from the completed items can be computed.

For example, consider person X who has completed 15 items in the physical scale. Sum the completed items and divide by 15 to get person X’s respondent–specific mean score. Then use this value as the score for EACH of the missing 5 items. Then generate a total score as usual by summing the values of the 15 completed items and the 5 imputed items.
Note: respondents MUST have completed a minimum of 10 items in the physical scale, or 5 items in the psychological scale to use this imputing process.

It is copyrighted, ‘© 2006 University of Plymouth, University College London and Plymouth Hospitals NHS Trust. All Rights Reserved.’ Available in many languages.

  • Hobart J, Lamping D, Fitzpatrick R, Riazi A, Thompson A. The Multiple Sclerosis Impact Scale (MSIS-29): a new patient-based outcome measure. Brain 2001;124:962-73.

 

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