Complex regional pain syndrome - Diagnosis 

There is no single diagnostic test for complex regional pain syndrome (CRPS). The condition is usually diagnosed through a process known as "diagnosis of exclusion". This means that a confident diagnosis can only be made after other conditions that can cause similar symptoms have been ruled out through testing.

Tests

Possible tests used to rule out other conditions are:

• blood tests, which can rule out an underlying infection or rheumatoid arthritis (a condition that causes pain and inflammation in the joints)
• a magnetic resonance imaging (MRI) scan, where a strong magnetic field and radio waves are used to produce detailed images of the inside of your body, which can help to rule out underlying problems with your tissue or bones
• a biopsy, where a small tissue sample is removed and checked for the presence of abnormal cells
• an X-ray, an imaging technique that uses high-energy radiation to highlight bone and tissue abnormalities, and can help to rule out problems with the joints and bones

There are other tests that, while they cannot prove that you have CRPS, may indicate that there is a good chance that you have developed it. These are described below.

• A physical examination, where your GP or another specialist will check for physical signs of CRPD, such as swollen joints, and changes to your skin’s temperature and appearance.
• Sweat testing, where the sweat that is produced by both your affected limb and an unaffected limb is measured. A large difference between the two readings could indicate CRPS.
• Thermography, where an infrared thermometer is used to measure your skin temperature at different parts of your body. If your affected limb has a much higher, or lower, skin temperature than the rest of your body, it could indicate CRPS.
• Electrodiagnostic testing, which involves a series of tests where wires are attached to your skin in order to measure the electrical activity of your nerves. Abnormal readings may suggest that your nerves are damaged, and that you have type two CRPS.

Diagnostic checklist

As CRPS can be a difficult condition to diagnose, experts in the field have created a checklist to assist GPs and other healthcare professionals when making a diagnosis.

A diagnosis of CRPS can be made if all of the following signs and symptoms are present:

• You have recently experienced an injury or other type of trauma.
• You have ongoing pain in a limb that is disproportionate to the original injury or trauma.
• There is physical evidence of swelling, and changes to your skin temperature and appearance.
• No other diagnosis would better explain your signs and symptoms.

Referral

If you are diagnosed with CRPS, you may be urgently referred to a specialist pain clinic. There are around 300 pain clinics in the UK, which are mostly located in hospitals. An urgent referral ensures that treatment can be started immediately, because the earlier your treatment is started, the less likely it is that you will experience any long-term disability.