Reconstructing the Rasch-Built Myotonic Dystrophy Type 1 Activity and Participation Scale.
BACKGROUND
A previously published Rasch-built activity and participation scale specifically designed for patients with myotonic dystrophy type 1 (DM1) was criticized for having been constructed in a relatively small cohort of patients and containing items too broadly phrased for DM1 patients, thus hampering its clinical use.


METHODS
We report the results of the reconstructed Rasch-built DM1 activity and participation scale for clinical use (DM1-ActivC) through Rasch analyses using an expanded questionnaire containing 146 more simply phrased activity and participation inquiries completed by 340 patients with DM1.


RESULTS
Through stepwise investigation including data quality control, model fit, response category ordering, local dependency and item bias, we succeeded in reconstructing the DM1-ActivC consisting of 25 items that showed good Rasch model fit, including construct convergent validity, items' weights and persons' locations reliability, and unidimensionality.


CONCLUSIONS
The DM1-ActivC scale has been reconstructed and fulfills all modern clinimetric requirements. Its use is recommended in future longitudinal trials in patients with DM1 to determine its responsiveness.
Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands.
Mieke C E
MC
Hermans
Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands.
Janneke G J
JG
Hoeijmakers
Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands.
Catharina G
CG
Faber
Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands; Department of Neurology, Spaarne Hospital, Hoofddorp, The Netherlands.
Ingemar S J
IS
Merkies
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009223:Myotonic Dystrophy / Q000175:diagnosis / Q000503:physiopathology*; D011594:Psychometrics; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult