A simple technique could help doctors differentiate between patients with different causes of back pain and thus improve treatment, a study suggests.
Researchers writing in PLoS Medicine have devised "bedside" tests which distinguish between neuropathic - nerve damage - and other causes of pain.
Neuropathic pain is commonly described as "burning" or "stabbing" but it is often difficult to formally diagnose.
Back pain is the most commonly cited reason for being absent from work.
A team from Massachusetts General Hospital in the US and Addenbrooke's in the UK recruited more than 300 patients with chronic back pain.
Some had a known history of nerve damage caused by diabetes or shingles, while others had low back pain with or without evidence of spinal nerve root damage.
By carrying out detailed comparisons of the patients, researchers were able to formulate a set of six questions and 10 physical tests which distinguished between the two groups.
The results, they said, were superior to existing screening tests for neuropathic pain and even to MRI scanning of the spine, which can be misleading as many people have damage to their spinal discs without any pain.
In most types of neuropathic pain, all signs of any injury have usually disappeared but certain nerves continue to send pain messages to the brain.
Traditional pain killers often do not help - other options include antidepressants, and physical as well as psychological treatment.
"Currently clinicians measure pain only by asking how bad it is, using scales from mild to moderate to severe or asking patients to rate their pain from one to 10," said lead author Joachim Scholz, an assistant professor of anaesthesia.
"This approach misses key characteristics that reflect the mechanisms causing the pain.
"The treatment of neuropathic and nonneuropathic pain is quite different, and if a diagnosis is wrong, patients may receive treatment, including surgery, that does not improve their pain."
Dries Hettinga, head of research & policy at the charity BackCare, said: "Although back pain is very common, in many cases we still have a poor understanding of where the pain is coming from and how to tailor treatments to individual cases.
"This is why the diagnostic tool that the researchers developed could make a big difference to many people with back pain.
"People with neuropathic back pain need a different treatment approach than those with non-neuropathic pain and an accurate and easy to use tool to distinguish the two types of pain would not only benefit people with back pain, but also help to tailor treatments for people with back pain and thus decrease costs."