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

Knutsson I, Rydström H, Reimer J, Nyberg P, Hagell P - Health Qual Life Outcomes (2010)

Bottom Line: 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.However, problems associated with raw rating scale data, primarily related to their ordinal structure also became apparent.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Health Sciences, Lund University, PO Box 157, SE-221 00 Lund, Sweden.

ABSTRACT

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.

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Response category mean VAS values and 95% CIs. Mean values (black dots) with associated 95% confidence intervals (error bars) for 100-mm visual analog scale (VAS) ratings (y-axis) of the perceived meaning of response category wordings (x-axis) in relation to (A) Never (0 mm) - Always (100 mm), (B) Not at all (0 mm) - Extremely (100 mm), and (C) Totally disagree (0 mm) - Completely agree (100 mm) among people with Parkinson's disease (n = 51) and an age-matched control group (n = 36). See Methods for details.
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Figure 1: Response category mean VAS values and 95% CIs. Mean values (black dots) with associated 95% confidence intervals (error bars) for 100-mm visual analog scale (VAS) ratings (y-axis) of the perceived meaning of response category wordings (x-axis) in relation to (A) Never (0 mm) - Always (100 mm), (B) Not at all (0 mm) - Extremely (100 mm), and (C) Totally disagree (0 mm) - Completely agree (100 mm) among people with Parkinson's disease (n = 51) and an age-matched control group (n = 36). See Methods for details.

Mentions: Results from the VAS evaluations of the 21 rating scale response categories from the pooled sample are presented in Table 1 and Figure 1, with categories organized in ascending order (from lower to higher mean VAS values) within each of the three response category types. Additional file 1 presents the corresponding data separately for people with PD and controls.


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

Knutsson I, Rydström H, Reimer J, Nyberg P, Hagell P - Health Qual Life Outcomes (2010)

Response category mean VAS values and 95% CIs. Mean values (black dots) with associated 95% confidence intervals (error bars) for 100-mm visual analog scale (VAS) ratings (y-axis) of the perceived meaning of response category wordings (x-axis) in relation to (A) Never (0 mm) - Always (100 mm), (B) Not at all (0 mm) - Extremely (100 mm), and (C) Totally disagree (0 mm) - Completely agree (100 mm) among people with Parkinson's disease (n = 51) and an age-matched control group (n = 36). See Methods for details.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2908570&req=5

Figure 1: Response category mean VAS values and 95% CIs. Mean values (black dots) with associated 95% confidence intervals (error bars) for 100-mm visual analog scale (VAS) ratings (y-axis) of the perceived meaning of response category wordings (x-axis) in relation to (A) Never (0 mm) - Always (100 mm), (B) Not at all (0 mm) - Extremely (100 mm), and (C) Totally disagree (0 mm) - Completely agree (100 mm) among people with Parkinson's disease (n = 51) and an age-matched control group (n = 36). See Methods for details.
Mentions: Results from the VAS evaluations of the 21 rating scale response categories from the pooled sample are presented in Table 1 and Figure 1, with categories organized in ascending order (from lower to higher mean VAS values) within each of the three response category types. Additional file 1 presents the corresponding data separately for people with PD and controls.

Bottom Line: 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.However, problems associated with raw rating scale data, primarily related to their ordinal structure also became apparent.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Health Sciences, Lund University, PO Box 157, SE-221 00 Lund, Sweden.

ABSTRACT

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.

Show MeSH
Related in: MedlinePlus