What initial investigations should be conducted to support a diagnosis of CRPS in a patient with suspected symptoms?

Initial investigations to support a diagnosis of complex regional pain syndrome (CRPS) should primarily focus on excluding other causes of the symptoms and assessing nerve involvement. There is no specific diagnostic test for CRPS; diagnosis is clinical and supported by history and examination.

Initial investigations may include:

• Clinical assessment of peripheral nerves in the affected limb to identify nerve involvement and functional deficits, as nerve injury can coexist or mimic CRPS symptoms.
• Consider nerve conduction studies or specialist neurological opinion if nerve injury is suspected and recovery is delayed or atypical.
• Basic blood tests to exclude other causes of pain and inflammation, such as full blood count, inflammatory markers (e.g., erythrocyte sedimentation rate, C-reactive protein), and metabolic panels.
• Imaging may be used to exclude fractures or other structural causes but is not diagnostic for CRPS itself.

Overall, investigations are aimed at excluding other diagnoses and assessing nerve function rather than confirming CRPS, which remains a clinical diagnosis.

References: This approach aligns with recommendations to assess nerve injury and exclude other causes in chronic pain and nerve injury guidelines NICE NG193,NICE NG211.