Asking patients in the emergency room to rate their pain on a visual scale or to rank it from zero to 10 doesn't really convey what the patient is feeling, suggests a study from Sweden.

Pain scales currently used in the ER focus on pain intensity, and miss other important aspects like the type of pain or whether it changes with body position, and many patients don't really understand what the extremes of the pain scales would feel like, researchers found.

"Some say that painkillers should be given on patients' request rather than based on a pain score," said senior author Dr. Therese Djarv of Karolinska Institute in Stockholm. "Likewise, up-triaging based on a pain score might be less relevant than based on the patient's whole experience of pain," she said by email.

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In the fall of 2012, two researchers interviewed patients waiting in the emergency department of Karolinska University Hospital with complaints of chest, abdominal or orthopedic pain. Participants were asked to rate their pain on a visual scale and a numeric scale.

The visual scale asks respondents to mark their pain level on a 10-centimeter (about 4 inches) horizontal line, and the numeric scale asks respondents to rate their pain from zero to 10 scale, with 10 being the most intense possible pain.

Then researchers interviewed the patients about how sufficient or insufficient the scales had been at rating their pain.

Some patients expressed that rating their pain at one time on one scale was insufficient because their pain levels changed over time.

One patient said, "When you have pain the scales are good, but not when the pain varies or comes and goes."

Some patients with chest pain complained that what they felt was pressure rather than pain. Others feared that rating their pain lower would mean their condition wouldn't be taken seriously, according to the report in the American Journal of Emergency Medicine.

"Pain is one of the few things physicians can't objectively measure," said Dr. John G. DeVine of the Department of Orthopaedic Surgery at Augusta University in Georgia, who was not part of the new study.

"Each patient's perception of pain is influenced by several variables (anxiety, depression, cultural upbringing, acute vs chronic symptoms, etc)," DeVine told Reuters Health by email. "As physicians, the actual number used to describe the pain is probably less important than the location, pattern, onset, and the ability of the patient to change these (position, medications, etc)."

"The scales used are well validated and used on postoperative and chronic pain, however, the pain in the (emergency department) differs from such pain because it is of unknown origin and severity," Djarv said. The scales may need to be retested and validated in the emergency department, she said.

Patients should be honest with their ratings, she added. "If the rating does not make sense to you, speak up and ask the personnel," Djarv said. "Do not guess how to do it."