Introduction: About 77% of adults with stroke have upper limb impairments. Many upper limb measures are available for adults with stroke to measure the impairment and activity level of the affected limb. However, an observational scale focused on assessing dependency in upper limb use during daily life activities (as opposed to testing in laboratory settings) is lacking. To bridge this gap, we have developed a new 5-item Upper Limb Lucerne ICF-based Multidisciplinary Observation Scale (UL-LIMOS), which assesses dependency on others during affected arm use in daily life in adults with stroke. As a next step in the psychometric analysis, we evaluated the unidimensionality and structural validity of the UL-LIMOS with Rasch Measurement Theory. Methods: This is a single-center cross-sectional study in adults with (sub)acute stroke. We applied Rasch Measurement Theory (RMT) to analyze the structural validation and unidimensionality of the new UL-LIMOS. We chose a polytomous partial credit model using the Rasch Unidimensional Measurement Model (RUMM) 2030 software. The outputs provide evidence of unidimensionality, item and person fit, overall fit, principal component analysis of residuals (PCAR), person separation reliability (PSR), as well as residual item correlations to identify local item dependence. Person mean location, floor and ceiling effects identify proper targeting. Results: We recruited 407 adults with (sub)acute stroke (median age 63 years, 157 women). All items and persons fit the Rasch model, and the PSR of 0.90 indicates that clinicians and researchers can reliably use the scale for individual decision-making. There were small floor (2.70%) and ceiling (13.00%) effects. The average person mean location was 1.32 +/- 2.99 logits, indicating that the items were too easy for this group of adults with (sub)acute stroke. The PCAR eigenvalue was 2.46 with 49.23% explained variance. Further analysis of paired t-tests revealed that 0.89% of person locations were significantly different when comparing the two subtests formed based on positive and negative loadings on the first principal component, thereby confirming the unidimensionality of the scale. One pair of items related to arm and hand use and fine hand use showed residual item correlations. Discussion: The new Rasch-based UL-LIMOS is a valid ICF-based observation scale at the ICF-participation level, to evaluate dependency during upper limb use in daily life in adults with stroke. The UL-LIMOS would be a valuable addition to the core assessments of adults with (sub)acute stroke in hospitals and rehabilitation centers. Further analysis is needed to generalize our findings to adults with chronic stroke who have returned to their home setting, and in other countries to account for cultural differences. Targeting could be improved in the future. Additional psychometric analyses, such as sensitivity to change, are warranted. A comparison of the UL-LIMOS data with self-reported measurements or accelerometers could potentially lead to changes to the core datasets recommended for the evaluation of adults with stroke.

The authors have declared no competing interest.

This study was supported by Swiss National Science Foundation grants (T.N. 320030_140696 and 320030_169789) and Innosuisse grant (T.V. 52272.1 IP-SBM).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was conducted in accordance with the principles of the Declaration of Helsinki (2013) and was approved by the local Ethical Committees of the state of Luzern (BASEC-ID 2017-00998). We followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement (29). The participants gave written informed consent. A family member with power of attorney consented if participants had severe cognitive impairments, preventing them to consent independently.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes

Original datasets requests can be directed to the first or last author.