Stability of the visual analogue scale in stress assessment

Aim of the study. The visual analogue scale (VAS) has been proposed for about 10 years to assess occupational psychological distress. Some validation data have already been reported, such as the correlation with Karasek's model. But numerous parameters have still to be validated. One fundamental point in a scale assessment is the analysis of the reproducibility and sensitivity. The aim of this study is to evaluate the 1-year stability of this VAS. Patients and methods. We followed up 576 civil servants (police officers and university staff) during 2 years. The occupational physician used a VAS in 2006 and 2007. Five hundred and fourteen paired subjects were included (paired observations without identified stressful event). The 1-year stability of the VAS was assessed using the Bland and Altman method. Results. VAS scores in 2006 and 2007 do not follow a normal distribution. There is no statistically significant difference between the mean scores in 2006 and 2007. The repeatability coefficient is 95.14%. Discussion. The results suggest a good repeatability of the VAS. We really measure a stable psychological dimension. The answers to the VAS are not due to a random choice. It is the first step in the validation of the VAS. Some others parameters such as the inter-judge reproducibility or the convergent validity have to be analysed. (C) 2009 Elsevier Masson SAS. All rights reserved.