Predictors of a child's ability to use a visual analogue scale

Background Visual analogue scales (VAS) are used to assess the strength of perceptions of both children and adults in many clinical and research settings. Although the VAS has been shown by some authors to be reliable for use by children aged 5 years and older, others have proposed that young children, generally less than or equal to7 years of age, may not have the conceptual ability to use a VAS. Objective To identify demographic and cognitive variables that would maximize the accuracy of predicting children's abilities to use a VAS. Methods Forty kindergarten children performed a seriation task, used a VAS to perform a calibration task and completed the Block Design and Vocabulary subtests of the Wechsler Preschool and Primary Scale of Intelligence - Revised (WPPSI-R). An estimated IQ was calculated from the WPPSI-R subtest scores. Socioeconomic status was assessed using the Hollingshead Four Factor Index of Social Status. Logistic regression was used to determine the best predictive models. Sensitivity, specificity, negative predictive value, positive predictive value and accuracy were calculated for statistically significant predictive models. Main outcome measure Successful completion of the calibration study by the child. Results Only 42% of the subjects could use a VAS. The subject's age (greater than or equal to5.6 years), combined with estimated IQ (greater than or equal to100), was the best predictor of a child's ability to use a VAS (88% accuracy). Conclusion The majority of kindergarten children in our study could not complete a VAS accurately. Cognitive ability, combined with chronological age, was the best predictor of a child's accurate use of a VAS, as determined by logistic regression. Paediatric researchers may need to consider alternative rating scales to measure perceptions in children under 7 years of age.