From the Guidelines
To calculate a Visual Analog Scale (VAS) score, measure the distance in millimeters from the left anchor of the scale to the mark drawn by the participant, with scores ranging from 0 to 100 or 0 to 10, as described in the study by 1. The VAS is a simple and effective tool for assessing pain intensity, with higher scores corresponding to higher pain intensity.
- The score is calculated as the measured distance in millimeters between the left anchor of the scale and the mark drawn by the participant.
- The VAS takes under 1 minute to complete, and its validity has been established in various studies, including one that found evidence of moderate-convergent validity, adequate discriminant validity with fatigue ratings, and adequate concurrent validity with pain catastrophizing ratings 1. Some key points to consider when using the VAS include:
- Score interpretation, where higher scores correspond with higher pain intensity, with typical interpretations being 10 to 30 as mild pain, 40 to 60 as moderate pain, and 70 to 100 as severe pain 1.
- The minimally important difference of the VAS is 10 to 12 mm, as reported in the study by 1.
- The VAS requires low burden for in-person assessments and can be easily administered with minimal training, which typically takes less than 1 minute 1.
From the Research
Calculating VAS Score
To calculate the Visual Analog Scale (VAS) score, the following steps can be taken:
- The VAS is a continuous scale composed of a horizontal or vertical line, usually 10 cm in length, with two extremes of pain, namely "no pain" and "worst pain" 2.
- Patients mark a point on the line that corresponds to their current level of pain.
- The VAS score is then calculated by measuring the distance from the "no pain" end to the point marked by the patient.
Interpreting VAS Scores
The interpretation of VAS scores can be done using the following categories:
- No pain: 0-2 mm
- Mild pain: 2-17 mm
- Moderate pain: 17-47 mm
- Severe pain: 47-77 mm
- Very severe pain: 77-96 mm
- Most severe pain imaginable: 96-100 mm 2
Analyzing VAS Scores
When analyzing VAS scores, it is essential to consider the level of measurement, which can be either ratio or ordinal 3, 4.
- If the VAS score is considered ratio data, parametric statistical methods can be used.
- If the VAS score is considered ordinal data, non-parametric statistical methods, such as continuous ordinal regression, should be used 4.
- Distribution-free methods, such as the Wilcoxon or Mann-Whitney test, can also be used to analyze VAS scores, especially when there are no covariates besides treatment group 4.
Clinical Relevance
The VAS score has been shown to be a reliable and valid measure of pain intensity in various clinical settings, including headache and acute mountain sickness 2, 5.
- The VAS score can be used to evaluate the effectiveness of treatments and to monitor changes in pain intensity over time.
- The minimal clinically important difference in VAS scores has been estimated to be around 1.4 cm, which can be used to determine the clinical significance of changes in VAS scores 6.