Review question
What are the benefits and harms of plasma exchange for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)?
Background
CIDP is an uncommon paralysing disease caused by inflammation of the peripheral nerves. Plasma exchange, also called plasmapheresis, removes blood from one vein, passes it through a machine, and then returns it into another vein. The machine replaces the plasma, which is the fluid part of the blood, with a substitute and preserves the red blood cells. The procedure removes potentially harmful substances, including antibodies. It takes several hours and is usually repeated about five times over two weeks. We wanted to discover whether plasma exchange is helpful in CIDP.
Study characteristics
We found two randomised controlled trials. Both studies compared plasma exchange with sham exchange (in which blood was removed and returned but not exchanged). One trial aimed to compare four weeks' plasma exchange with sham exchange. The 18 participants received both treatments, being randomised to either treatment in the first period of the trial, crossing over to the other treatment for the second period. The other trial compared three-weeks' plasma exchange in 15 participants with sham exchange in 14 participants. We considered both trials at low risk of bias, which means largely free of flaws that could have influenced the results.
Study funding sources
A charitable grant supported the cross-over trial. The other did not report any support.
Key results
The cross-over trial showed on average two points more improvement on an 11-point disability scale with plasma exchange than sham exchange. This was unlikely to have occurred by chance. The parallel-group trial did not report this outcome. When we combined the results of both trials, plasma exchange produced significantly more improvement in severity of disease signs measured by neurologists than sham exchange. The results reported were short term. In practice, people with CIDP receive repeated courses or combinations of plasma exchange with additional agents. Another Cochrane review includes a trial showing similar improvement after plasma exchange to that after intravenous infusion of immunoglobulin (the antibody portion of blood). According to non-randomised evidence, plasma exchange causes adverse events in 3% to 17% of procedures. These are sometimes serious.
Quality of the evidence
Because of the small size of the only trial reporting changes in disability, the quality of the evidence that plasma exchange reduces disability is moderate. The quality of the evidence that plasma exchange improves the signs of disease measured by a neurologist is high.
The evidence is up to date to 30 June 2015.
Moderate- to high-quality evidence from two small trials shows that plasma exchange provides significant short-term improvement in disability, clinical impairment, and motor nerve conduction velocity in CIDP but rapid deterioration may occur afterwards. Adverse events related to difficulty with venous access, use of citrate, and haemodynamic changes are not uncommon. We need more research to identify agents that will prolong the beneficial action of plasma exchange.
Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an uncommon progressive or relapsing paralysing disease caused by inflammation of the peripheral nerves. If the hypothesis that it is due to autoimmunity is correct, removal of autoantibodies in the blood by plasma exchange should be beneficial.
To assess the effects of plasma exchange for treating CIDP.
On 30 June 2015, we searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register for Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL Plus, and LILACS. We also scrutinised the bibliographies of the trials, contacted the trial authors and other disease experts, and searched trials registries for ongoing studies.
Randomised controlled trials (RCTs) or quasi-RCTs in participants of any age comparing plasma exchange with sham treatment or no treatment.
Two review authors independently selected the trials, extracted the data, and assessed risk of bias. Where possible the review authors combined data according to the methods of the Cochrane Neuromuscular Disease Review Group.
Primary outcome measure: one cross-over trial including 18 participants showed after four weeks, 2 (95% confidence interval (CI) 0.9 to 3.1) points more improvement on an 11-point disability scale with plasma exchange (10 exchanges over four weeks) than with sham exchange. Rapid deterioration after plasma exchange occurred in eight of 12 who had improved.
Secondary outcome measures: when we combined the results of this cross-over trial and a trial with 29 participants treated in a parallel-group design, there were 31 points (95% CI 18 to 45) more improvement on an impairment scale (maximum score 280) after plasma exchange (six exchanges over three weeks) than after sham exchange. There were significant improvements in both trials in an electrophysiological measure, the proximally evoked compound muscle action potential, after three or four weeks. Non-randomised evidence indicates that plasma exchange induces adverse events in 3% to 17% of procedures. These events are sometimes serious. Both trials had a low risk of bias. A trial that showed no significant difference in the benefit between plasma exchange and intravenous immunoglobulin is included in the Cochrane review of intravenous immunoglobulin for this condition.