Assessing the Value of the Pain Intensity Assessment Tools

CLEVELAND, Ohio—When cancer is diagnosed, most patients fear pain more than any other symptom, Victoria Lipnickey, PA-C, said at a symposium on palliative medicine, sponsored by the Cleveland Clinic Foundation.

Accurately assessing pain is very important, said Ms. Lipnickey, of the Cleveland Clinic’s Harry R. Horvitz Center for Palliative Medicine. A complete pain evaluation must identify the location of the pain, time of onset, duration, its quality (throbbing or lancinating, for instance), and alleviating and exacerbating features. “The characteristics of pain must be discussed every time pain is discussed, as these qualities often change as the cancer progresses,” she said.

An assessment of pain should include subjective features. The clinician should always ask how the pain affects the patient’s quality of life. “This is likely to be a very important issue for the patient,” Ms. Lipnickey said.

Pain assessment tools record the patient’s own report of pain. These tools measure only a single dimension of pain: intensity. However, they can be used to provide an ongoing assessment of pain as well as measure the alleviating effects of treatment.

The advantage of the single-dimension scales is their ease of use for both the patient and clinician. These scales are pocket-sized, easy to understand, inexpensive, and readily available.

The disadvantage is that there is a risk of oversimplifying the patient’s experience of pain, Ms. Lipnickey said. “The patient may feel that you care more about the number than the pain’s effect on the patient’s life,” she said.

Pain assessment scales include the verbal rating scale, visual analog scale, numerical rating scale, behavior rating scale, picture scale, box scale, and descriptor differential scale.

Numerical Rating Scale

With the numerical rating scale, the patient rates pain on a scale from 0 to 10 (or 100), with 0 representing no pain and the highest number representing the worst imaginable pain.

The advantage of the numerical rating scale is that it has been proved to have high consistency, even with different clinicians administering the scale, Ms. Lipnickey said. It is a useful way to measure past episodes of pain, such as incident pain or pain that was felt prior to taking medication.

Its disadvantages are that few validation studies have been conducted using it, and those only with chronic pain. No validation studies have been conducted with cancer pain.

The verbal rating scale asks patients to select descriptive adjectives for their pain. Typically there are three to six adjectives on the list, ranging from “no pain” to “severe pain.”

The advantages of the verbal scale are that it is easy to use and evidence exists for its validity. However, one disadvantage is that the patient needs to read the entire list of adjectives before making a judgment. It is also difficult to make comparisons if a different rating scale is used on subsequent visits. For patients with limited vocabulary or limited vision, the usefulness of the visual rating scale is sharply curtailed, and it becomes less reliable, Ms. Lipnickey said.

With the visual analog scale, patients are shown a 10 cm line with ends labeled as extremes of pain. The patients are asked to mark a point on the line that corresponds with their sensation of pain. The clinician scores the scale by measuring the distance from “no pain” to the patient’s mark.

The visual analog scale is easy to administer, and good evidence exists for its validity. It is more difficult for patients to understand and use than the other scales, however, and there is a greater chance for error when the clinician scores the result, Ms. Lipnickey said. Also, use of this scale is difficult for the sight-impaired and physically challenged.

Behavior Rating Scale

The behavior rating scale asks patients to rate the intensity of their pain and to describe how pain interferes with the performance of everyday tasks. This discussion of the effect of pain on their lives may make this scale more meaningful to patients, she said.

The drawbacks of the behavior rating scale, however, are that some patients may confuse pain intensity with pain interference. If they suffer from depression, for instance, that may affect how they score the behavior rating scale.

The picture scale displays five line drawings of facial expressions registering different levels of pain intensity. The faces may be cartoon-like (for young patients) or may show the face of an older man (for adult patients).

The advantage of the picture scale is that it is easy to administer and score. It is useful when working with children or adults with cognitive impairment. It may also be recommended when a language barrier exists between clinician and patient, Ms. Lipnickey said.

The disadvantage of the picture scale is that it is not widely used. Limited evidence exists for its validity, and no evidence exists regarding compliance rates. Also, the scale does not take into account cultural and ethnic differences in facial expressions.

Box Scale

The box scale is a combination of the numerical rating scale and the visual analog scale. Numbers ranging from 0 (no pain) to 10 (pain as bad as it could be) are displayed inside boxes, and patients are asked to put an “x” in the box that corresponds with their level of pain.

For some reason, the box scale is easier for older patients to use, Ms. Lipnickey said. It is easy to administer and score; preliminary evidence supports validity; and when used with patients consistently, it has high compliance rates.

One of the disadvantages of this scale is the limited number of response categories. It is not widely used, and, as with the visual analog scale, its usefulness with sight-impaired or physically challenged patients is limited.

Descriptor Differential Scale

The descriptor differential scale is a list of 12 adjectives of pain intensity. The patient rates pain intensity in each of the 12 categories according to a 10-point scale.

The advantages of this scale are that it has high internal consistency and high re-test stability. The disadvantages are that it is time consuming, difficult to complete, and not yet evaluated for treatment sensitivity. “It is a very cumbersome scale and can be overwhelming for the patient,” Ms. Lipnickey said.