A series of simple bedside tests could help doctors to tailor a patient's treatment of back pain by distinguishing the pain's type rather than just determining how much it hurts, researchers say.

Chronic pain is common and nearly 10 per cent of American adults have frequent back pain, said the editors of journal PloS Medicine, in which the research is published this week.

Doctors typically measure pain by asking the patient to rate it on a scale of one to 10, a technique that is silent on important characteristics that would describe the nature of the pain and give clues as to what could be causing it.

Dr. Joachim Scholz of Massachusetts General Hospital in Boston and his colleagues used a new system to evaluate the pain suffered by 187 patients with a known condition.

Doctors took medical histories and examined the participants, conducting 23 simple tests that can be done at the bedside in about 15 minutes.

Some of the questions and tests probed what causes the pain, such as touch, activity, pressure or cold.

The standardized evaluation of pain or StEP, quickly distinguishes between two major types of pain:

• Peripheral neuropathic or "radicular" low back pain, also called sciatica, which radiates from the back into the legs.
• Axial back pain, the most common type of low back pain, which is confined to the lower back and is non-neuropathic, meaning it is not caused by damage to the brain or spinal cord.

"This distinction is crucial," the researchers said. "It is often difficult to decide which patients will benefit from treatment strategies that target neuropathic pain."

The new test was also better than an existing screening test for neuropathic pain, including spinal MRI, the researchers said.

Pain management

Each type of pain requires a different pain management strategy, and the difference is also important in testing new drugs, Giorgio Cruccu and Andrea Truini from La Sapienza University in Rome, Italy, said in a review accompanying the study.

"We badly need an objective measure of pain intensity and response to treatment," concluded Cruccu and Truini, who were not involved in developing the new tool.

"The only method that seems reasonably likely to solve this problem is functional neuroimaging. Yet it will not do so today — only in the future, once it succeeds in providing reliable measures at the individual level and becomes standardized and widely accessible."

Next, Scholz's team hopes to test how patients with different types of pain respond to tailored treatments, rather than largely guessing as is currently the case, they said.