Adaptation of Oxford Cognitive Screen into Turkish (OCS-TR): Validity and reliability study in stroke survivors

The existing cognitive screening tests used to assess cognitive disorders after stroke in Türkiye face limitations in scope and user applicability. Therefore, this study aimed to address these limitations by adapting the stroke-specific cognitive screening test, the Oxford Cognitive Screen (OCS), into Turkish. Additionally, validity and reliability studies were conducted.

A total of 114 stroke survivors and 92 healthy individuals participated in the study. Data were collected using the "Participant Information Form," "Oxford Cognitive Screen Turkish Version (OCS-TR)," "Aphasia Language Assessment Test (ADD)," "Montreal Cognitive Assessment Test- Turkish (MOCA-TR)," "Barthel Activities of Daily Living Index (BGYAI)" and "Beck Depression Scale." The team followed an established and detailed step by step process guided by the OCS Concept Elaboration document. Statistical analyses were conducted with IBM SPSS Statistics. Validity and reliability studies, including content validity, known-groups validity, convergent and divergent validity, concurrent validity, internal consistency reliability, test-retest reliability, inter-rater reliability, intra-rater reliability, and parallel forms reliability were conducted to assess the robustness of the measurement instruments.

The language and cultural adaptation process underwent content analysis, adhering to ISPOR and ISOQOL guidelines, resulting in minimal content changes post-pilot study. Notable differences in subtest scores between healthy and stroke participants in both A and B forms of OCS-TR demonstrate known-groups validity, emphasizing superior performance in healthy participants. Strong convergent validity was evidenced by significant correlations with MOCA-TR (r_s=0.18 to 0.81) and BGYAI (r_s=0.19 to 0.51), while divergent validity was supported by weak correlations with overall BGYAI scores. Noteworthy correlations between specific subtests of OCS-TR and ADD underscore concurrent validity, with high inter- and intra-rater reliability,  internal consistency (α = 0.90 for stroke, α = 0.65 for healthy) and test-retest reliability (r_s=0.89 to 0.99). Parallel forms reliability was high in both healthy and stroke participants, though significant differences were observed on specific subtests.

The results confirm that the OCS-TR scale can be considered a valid and reliable instrument for assessing cognitive functions in stroke survivors. This stroke-specific tool offers clinicians a comprehensive and inclusive brief cognitive screening tool tailored to the needs of stroke patients.