Interpretation of response categories in patient-reported rating scales: a controlled study among people with Parkinson's disease.

BACKGROUND: Unambiguous interpretation of ordered rating scale response categories requires distinct meanings of category labels. Also, summation of item responses into total scores assumes equal intervals between categories. While studies have identified problems with rating scale response category functioning there is a paucity of empirical studies regarding how respondents interpret response categories. We investigated the interpretation of commonly used rating scale response categories and attempted to identify distinct and roughly equally spaced response categories for patient-reported rating scales in Parkinson's disease (PD) and age-matched control subjects. METHODS: Twenty-one rating scale response categories representing frequency, intensity and level of agreement were presented in random order to 51 people with PD (36 men; mean age, 66 years) and 36 age-matched controls (14 men; mean age, 66). Respondents indicated their interpretation of each category on 100-mm visual analog scales (VAS) anchored by Never--Always, Not at all--Extremely, and Totally disagree--Completely agree. VAS values were compared between groups, and response categories with mean values and non-overlapping 95% CIs corresponding to equally spaced locations on the VAS line were sought to identify the best options for three-, four-, five-, and six-category scales. RESULTS: VAS values did not differ between the PD and control samples (P = 0.286) or according to educational level (P = 0.220), age (P = 0.220), self-reported physical functioning (P = 0.501) and mental health (P = 0.238), or (for the PD sample) PD duration (P = 0.213) or presence of dyskinesias (P = 0.212). Attempts to identify roughly equally spaced response categories for three-, four-, five-, and six-category scales were unsuccessful, as the 95% CIs of one or several of the identified response categories failed to include the criterion values for equal distances. CONCLUSIONS: This study offers an evidence base for selecting more interpretable patient-reported rating scale response categories. However, problems associated with raw rating scale data, primarily related to their ordinal structure also became apparent. This argues for the application of methodologies such as Rasch measurement. Rating scale response categories need to be treated with rigour in the construction and analysis of rating scales.

Review article: health impact assessment developments in Sweden.

AIMS: The contextual prerequisites in a country are crucial to the implementation and effectiveness of health impact assessment (HIA). This article aims to show how the Swedish government has been working to create supportive contextual prerequisites for HIA. These prerequisites are described based on the following factors: stewardship, including public health policy, party politics and legal preconditions; organization, including resources and funding; and delivery, which is dependent on the public health culture. The aim has also been to draw conclusions about facilitators of and obstacles to HIA implementation. METHODS: The article is based on a review of relevant literature. RESULTS: Since 2000, the Swedish government has taken a number of initiatives to increase the application of public health and HIA. National agencies and all of Sweden's county administrative boards have received government assignments with the National Institute of Public Health in a supportive role. CONCLUSIONS: Some facilitators of HIA implementation are: utilizing existing impact assessment knowledge; connecting HIA with the concept of a sustainable social development; and awareness of the time needed to adopt complex information. Obstacles detected are: the lack of a mandatory law for HIA; a lack of funding; and an occasional lack of public health skills. The final conclusion is that the public health policy adopted by the Swedish Riksdag, with its overarching aim of equality in health and its 11 domains of objectives, has had a crucial effect as a framework for HIA in Sweden.