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Aims and objectives. This review aims to explore the research available relating to three commonly used pain rating scales, the Visual Analogue Scale, the Verbal Rating Scale and the Numerical Rating Scale. The review provides information needed to understand the main properties of the scales.
Background. Data generated from pain-rating scales can be easily misunderstood. This review can help clinicians to understand the main features of these tools and thus use them effectively.
Method. A MedLine review via PubMed was carried out with no restriction of age of papers retrieved. Papers were examined for methodological soundness before being included. The search terms initially included pain rating scales, pain measurement, Visual Analogue Scale, VAS, Verbal Rating Scale, VRS, Numerical/numeric Rating Scale, NRS. The reference lists of retrieved articles were used to generate more papers and search terms. Only English Language papers were examined.
Conclusions. All three pain-rating scales are valid, reliable and appropriate for use in clinical practice, although the Visual Analogue Scale has more practical difficulties than the Verbal Rating Scale or the Numerical Rating Scale. For general purposes the Numerical Rating Scale has good sensitivity and generates data that can be statistically analysed for audit purposes. Patients who seek a sensitive pain-rating scale would probably choose this one. For simplicity patients prefer the Verbal Rating Scale, but it lacks sensitivity and the data it produces can be misunderstood.
Relevance to clinical practice. In order to use pain-rating scales well clinicians need to appreciate the potential for error within the tools, and the potential they have to provide the required information. Interpretation of the data from a pain-rating scale is not as straightforward as it might first appear.
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Pain rating scales have a fundamental place in clinical practice. The evidence suggests that patients are able to use them to communicate their pain experience and their response to treatment. The interpretation of pain scores is not straightforward. The key to successful pain management hinges upon the ability of the patient to use the tools made available, and the careful interpretation of the scores by the health care professionals.
Pain intensity is probably the easiest dimension of pain to assess, but it is not so easy to interpret the intricacies of the results. Patients communicate far more information about their pain than just intensity when using a pain rating scale.
All three of the pain-rating scales explored in this review are reliable and valid. The VAS is statistically the most robust as it can provides ratio level data. However, the data are not always normally distributed, and patients do not always use all of the scale. Repeated scores using the VAS can vary by as much as 20%. This could contribute to the clinically significant reduction in pain, suggested to be approximately 30–33%. The VAS is the most difficult of the three scales to use in clinical practice and has the highest failure rate.
The VRS is the least sensitive tool of the three, but it is easy to use. One of the biggest concerns about this tool is that the rank numbers assigned for ease of recording can mislead the clinician about the level of data that the tool provides. The VRS has not been extensively researched, but it is probably reliable and valid.
The NRS provides interval level data and is as sensitive as the VAS. The scale is easy to administer, record, and allows patients to use either 11 or 21 points of intensity.
Patients prefer the NRS when they want sensitivity and the VRS for simplicity but the evidence is not conclusive. The least favourite tool is the VAS, which is also the hardest tool to use and has the highest failure rate. In clinical practice the NRS or the VRS are both appropriate. As a tool for pain assessment as well as for audit and research the NRS is probably more useful than the VRS or the VAS.
Pain is entirely subjective and its links with pathology are indirect, the only way to successfully assess pain is to believe the patient. Pain is what the patient says it is (McCaffrey & Beebe 1989).