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Bias and precision in visual analogue scales: a randomized controlled trial
A Paul-Dauphin1, F Guillemin, J M Virion
1Ecole de Santé Publique, Faculté de Médecine, Vandoeuvre-les-Nancy, France.
American Journal of Epidemiology
|November 24, 1999
Summary
Visual analogue scales (VAS) impact measurement bias and precision. Scale characteristics affect results in cross-sectional studies, but not longitudinal analyses of change over time.
Area of Science:
- Epidemiology
- Clinical Research
- Biostatistics
Background:
- Visual analogue scales (VAS) are widely used in health research.
- Variations in VAS design and orientation may affect data quality.
- Standardization is needed for comparing results across studies.
Purpose of the Study:
- To evaluate the impact of different VAS types and orientations on measurement bias and precision.
- To compare VAS performance in cross-sectional versus longitudinal analyses.
- To inform best practices for VAS selection in research.
Main Methods:
- Randomized controlled trial within the SU.VI.MAX prevention trial pilot study.
- Six VAS types and two orientations used to measure ENT symptoms in 870 subjects.
- Statistical analysis included variance and repeated measures analysis.
Main Results:
- Scale characteristics influenced the proportion of zero and low scores (floor effect).
- Measurement precision varied cross-sectionally based on VAS type.
- No significant differences in the precision of measuring change over time were found.
Conclusions:
- VAS characteristics are crucial for cross-sectional studies, especially for low/high intensity symptoms.
- No differences in longitudinal precision suggest VAS type may be less critical for change measurement.
- A consensus on VAS usage is recommended for improved study comparability.