What is the problem and what is known about it so far?
Complex regional pain syndrome (CRPS) is an uncommon pain condition. It usually affects a limb after an injury. The main symptom is pain. In some instances, pain is mild and may eventually go away. In other instances, it is severe, persistent, and disabling. Effective treatments for patients with chronic disabling CRPS are needed.
Why did the researchers do this particular study?
To see whether treatment with low-dose immunoglobulin reduces pain more than placebo in adults with CRPS.
Who was studied?
111 adult patients with moderate or severe CRPS of 1 to 5 years' duration.
How was the study done?
Patients recorded daily pain intensity on a scale of 0 to 10 in a pain diary. They also completed questionnaires, at baseline and 6 weeks later, that assessed quality of life and whether pain interfered with activities. Patients were randomly assigned to receive 2 infusions of low-dose immunoglobulin (0.5 g/kg of body weight) or identical placebo given through a vein on days 1 and 22 after randomization. None of the patients, care providers, or researchers knew who received which treatment. Researchers then compared patients' reported pain intensity between days 6 and 42, as well as the other outcomes, between groups.
What did the researchers find?
The average pain intensity score at baseline for each group was about 7.5. All patients reported very low quality of life and that pain had a major effect on their everyday activities. Immunoglobulin infusions did not reduce pain. At follow-up, no clinically important differences were seen between groups in pain intensity, quality of life, or pain interference with activities. One patient who received immunoglobulin reported severe headaches. One patient who received placebo reported severe headaches and vomiting.
What were the limitations of the study?
The moderate-sized study could not examine whether particular subgroups of patients might benefit from treatment and tested only a low-dose treatment regimen.
What are the implications of the study?
Low-dose immunoglobulin treatment over 6 weeks does not relieve pain in patients with persistent, moderate to severe CRPS.