Common pain screening test often inaccurate

By Anne Harding

NEW YORK (Reuters Health) - A pain screening method widely used in US primary care settings is doing a poor job of identifying patients with serious pain, a new study suggests.

"It seemed to miss quite a few people, and it also didn't distinguish very well between people with very severe pain and people with not very severe pain," Dr. Erin E. Krebs of the Indiana University School of Medicine in Indianapolis, the study's lead author, told Reuters Health.

The Joint Commission on Accreditation of Healthcare Organizations (JCAHO), the main body that accredits US hospitals and clinics, requires its accredited institutions to assess patients for pain at every visit, Krebs and colleagues note in the October issue of the Journal of General Internal Medicine. JCAHO doesn't specify what type of screening test should be used, they add, but the most popular method involves asking a patient to rate their pain from 0 (no pain) to 10 (worst possible pain).

In the current study, researchers sought to determine if this numeric rating scale was an accurate way to spot patients with "clinically important" pain by comparing it to two different pain severity criteria: pain that interferes with functioning, and pain that motivates the patient to visit the doctor.

Among 275 primary care patients, pain was the main or secondary reason for the visit for 40 percent, the researchers found, while 37 percent of patients reported pain that interfered with their functioning. Twenty-six percent met both criteria.

But the researchers found that almost one-third of the patients with pain that interfered with functioning had a numeric rating scale score of 0, while 21 percent of those who reported pain as the primary reason for their visit scored 0 on the numeric rating test.

The numeric rating scale might fail to capture clinically important pain because it focuses on a patient's current level of pain, the researchers note; patients may also use different words to define what they are feeling. "For example," they note, "one participant reported difficulty answering the questions because 'I feel great discomfort, but it is different than pain.'"

The numeric pain test might be more appropriate to situations where pain is common, and patients are experiencing similar types of pain, such as after surgery, Krebs told Reuters Health. "In primary care, we have a lot of different kinds of pain," the investigator added. "It's really trying to measure apples and oranges and bananas all with the same screening test."

People seeing a doctor for pain should be as detailed as they can in describing it, advised Krebs, for example where they are feeling it and what it feels like. "Those are the kinds of things that help us make decisions about what might be causing the pain and how to address it."

SOURCE: Journal of General Internal Medicine, October 2007.