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The DCV method allowed quantitative assessment of each item and can therefore inform the content validity of the measures assessed. The methods can be applied to assess content validity before or after collecting data to select the appropriate items to measure theoretical constructs. Further, the data reported for each item in Appendix S1 can be used in item or measure selection. Statement of contribution What is already known on this subject? There are agreed methods of assessing and reporting construct validity of measures of theoretical constructs, but not their content validity. Content validity is rarely reported in a systematic and transparent manner. What does this study add? The paper proposes discriminant content validity (DCV), a systematic and transparent method of assessing and reporting whether items assess the intended theoretical construct and only that construct. In three studies, DCV was applied to measures of illness perceptions, control cognitions, and theory of planned behaviour response formats. Appendix S1 gives content validity indices for each item of each questionnaire investigated. Discriminant content validity is ideally applied while the measure is being developed, before using to measure the construct(s), but can also be applied after using a measure.

Background:Informal caregivers of patients with amyotrophic lateral sclerosis experience increased levels of caregiver burden as the disease progresses. Insight in the factors related to caregiver burden is needed in order to develop supportive interventions.Aim:To evaluate the evidence on patient and caregiver factors associated with caregiver burden in amyotrophic lateral sclerosis informal caregivers.Design:A systematic review.Data sources:Four electronic databases were searched up to 2017. Studies that investigated quantitative relations between patient or caregiver factors and caregiver burden were included. The overall quality of evidence for factors was assessed using the Grading of Recommendations Assessment, Development and Evaluation approach.Results:A total of 25 articles were included. High quality of evidence was found for the relation between caregiver burden and the factor “behavioral impairments.” Moderate quality of evidence was found for the relations between caregiver burden and the factors “feelings of depression” of the caregiver and “physical functioning” of the patient. The remaining rated caregiver factors—“feelings of anxiety,” “distress,” “social support,” “family functioning,” and “age”—and patient factors—“bulbar function,” “motor function,” “respiratory function,” “disease duration,” “disinhibition,” “executive functioning,” “cognitive functioning,” “feelings of depression,” and “age”—showed low to very low quality of evidence for their association with caregiver burden.Conclusion:Higher caregiver burden is associated with greater behavioral and physical impairment of the patient and with more depressive feelings of the caregiver. This knowledge enables the identification of caregivers at risk for caregiver burden and guides the development of interventions to diminish caregiver burden.

There is still a paucity of studies on psychological determinants of poststroke health-related quality of life. The reviewed studies supported the importance of psychological factors, but further research is needed to supplement the available evidence and to examine how psychological factors can be modified to improve health-related quality of life, and at what moment after the stroke these interventions should be given.