1. Background

Stroke is a frequently occurring condition and a common cause of death and disability. Many stroke survivors are facing long-term disability. The consequences of stroke on patients’ functioning are usually complex and heterogeneous. Precise knowledge of patients’ stroke related disability is necessary in health services provision and research. Clinical stroke management, but also epidemiological and clinical research, depend on the careful detection of functioning problems, as well as resources, in patients with stroke.

Two conceptual approaches to describe patients’ disability can be distinguished: the health status measurement and the classification approach. Health status measures, like standardized performance tests, rating scales, and questionnaires are used to operationalize and to assess patients’ burden of disease, functioning and health.

The classification approach towards the description of patients’ health state is represented by the World Health Organization’s International Classification of Functioning, Disability and Health (ICF). The ICF provides a comprehensive conceptual framework and a unified standardized language to describe health and health related states, both at the individual, as well as at population levels. To enhance the applicability of the classification, ICF Core Sets for specific health conditions have been developed in an evidence based and consensus based process. The ICF Core Sets for Stroke are selections of salient ICF categories out of the whole classification, which describe the spectrum of problems in stroke patients’ functioning based on the universal language of the ICF. The ICF Core Sets for Stroke represent the practical implementation of the classification approach in clinical practice and research.

The two approaches to represent stroke related disability, the health status measurement and the classification approach, can be regarded as complementary principles. From the classification perspective, the ICF and the ICF Core Sets can serve as standards to define what to measure. From the perspective of health status measurement the question how to measure can be answered.

An explicit connection between the two approaches can be established by the so-called linking method. Thereby, using the ICF’s category system the contents of measures can be mapped, explored and compared in a standardized, transparent and straightforward way. The linking method can be useful for various purposes. The application of the linking method along with the ICF Core Sets constitutes a new approach for examining health status measures’ content validity.

However, beyond content validity, meaningful measurement essentially depends on the psychometric quality of the applied instruments. Techniques based on modern test theory, especially Rasch analysis, are increasingly adopted to ensure instruments’ psychometric properties.

2. Objectives

In the following, the doctoral thesis is subdivided into four parts. The first three parts present different studies performed to pursue the objectives named below. Each of the three studies contains a respective discussion section referring to the results of the study. The fourth part of the doctoral thesis refers to aim four, namely the discussion of the relationship between the methods presented in the previous three parts.

The current doctoral thesis aims

(1) to illustrate, how the connection between the health status measurement approach and the classification approach can be established by the application of the linking method,

(2) to demonstrate, how this approach can be used to select health status measures based on their content validity,

(3) to show, how the psychometric features of health status measures can be examined based on Rasch analyses, and

(4) to discuss the relationship between the demonstrated methods in the context of the connection of the health status measurement and the classification approach.

3. Applying the linking method: