Visual Analogue Scale
Original Editor - Venus Pagare
Top Contributors - Venus Pagare, Kim Jackson, Khloud Shreif, Evan Thomas, Scott Buxton, Vanessa Rhule, Rebecca Willis, Admin, WikiSysop, Lauren Lopez and Melissa Coetsee
Introduction[edit | edit source]
A Visual Analogue Scale (VAS) is a measurement instrument that tries to measure a characteristic or attitude that is believed to range across a continuum of values and cannot easily be directly measured[1]. It is often used in epidemiologic and clinical research to measure the intensity or frequency of various symptoms.Cite error: Invalid <ref> tag; name cannot be a simple integer. Use a descriptive title For example, the amount of pain that a patient feels ranges across a continuum from none to an extreme amount of pain.[1] From the patient's perspective this spectrum appears continuous ± their pain does not take discrete jumps, as a categorization of none, mild, moderate and severe would suggest. It was to capture this idea of an underlying continuum that the VAS was devised.[1]
Structure and Orientation of the Scale[edit | edit source]
VAS can be presented in a number of ways,including:
- scales with a middle point,graduations or numbers (numerical rating scales),
- meter-shaped scales (curvilinear analogue scales),
- "box-scales,"scales consisting of circles equidistant from each other(one of which the subject has to mark),and
- scales with descriptive terms at intervals along a line (graphic rating scales or Likert scales) Cite error: Invalid
<ref>tag; name cannot be a simple integer. Use a descriptive title - The most simple VAS is a straight horizontal line of fixed length, usually 100 mm. The ends are defined as the extreme limits of the parameter to be measured (symptom,pain,health)Cite error: Invalid
<ref>tag; name cannot be a simple integer. Use a descriptive title orientated from the left (worst) to the right (best). In some studies,horizontal scales are orientated from right to left ,and many investigators use vertical VASCite error: Invalid<ref>tag; name cannot be a simple integer. Use a descriptive title. - No difference between horizontal and vertical VAS has been shown in a survey involving 100 subjectsCite error: Invalid
<ref>tag; name cannot be a simple integer. Use a descriptive title but other authors have suggested that the two orientations differ with regard to the number of possible angles of viewCite error: Invalid<ref>tag; name cannot be a simple integer. Use a descriptive title. Reproducibility has been shown to vary along a vertical 100-mm VAS and along a horizontal VAS Cite error: Invalid<ref>tag; name cannot be a simple integer. Use a descriptive title. The choice of terms to define the anchors of a scale has also been described as important.Cite error: Invalid<ref>tag; name cannot be a simple integer. Use a descriptive title
Administration[edit | edit source]
- They are generally completed by patients themselves but are sometimes used to elicit opinions from health professionals.
- The patient marks on the line the point that they feel represents their perception of their current state.
- The VAS score is determined by measuring in millimetres from the left hand end of the line to the point that the patient marks.[1]
Merits and Demerits[edit | edit source]
- VAS is more sensitive to small changes than are simple descriptive ordinal scales in which symptoms are rated,for example, as mild or slight,moderate,or severe to agonizing.
- These scales are of most value when looking at change within individuals
- However, assessment is clearly highly subjective
- Are of less value for comparing across a group of individuals at one time point.
- It could be argued that a VAS is trying to produce interval/ratio data out of subjective values that are at best ordinal.
Thus, some caution is required in handling such data. [1]
