Abstract
Background: This study investigated the ArmA-TH measurement properties based on item response theory, using the Rasch model. Methods: Patients with upper limb hemiplegia resulting from cerebrovascular and other brain disorders were asked to completed the ArmA-TH questionnaire. Rasch analysis was performed to test how well the ArmA-TH passive and active function sub-scales fit the Rasch model by investigating unidimensionality, response category functioning, reliability of the person and item, and differential item functioning (DIF) for age, sex and education. Results: Participants had stroke or other acquired brain injury (n=185) and the majority were men 126(68.1%), with a mean age of 55(SD 22). Most patients 91(49.2%) graduated elementary/primary school. For the ArmA-TH passive function scale, all items had acceptable fit statistics. The scale’s unidimensionality, and local independence were supported. The reliability was acceptable. Disordered threshold was found in five items, none was DIF. For the ArmA-TH active function scale, one item was misfitting and three were locally dependent. The reliability was good. DIF was not found. All items had disordered thresholds, and data fitted the Rasch model better after rescoring.Conclusions: Both sub-scales of ArmA-TH fitted the Rasch model, and are valid and reliable. The disordered thresholds should be further investigated.
Investigating Psychometric Properties of the Arm Activity Measure – Thai Version (ArmA-TH) Sub-Scales Using the Rasch Model
