Intravenous immunoglobulin for chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy is an immune mediated disorder characterised by progressive or relapsing symmetrical motor or sensory symptoms and signs in more than one limb, developing over at least two months. It may cause prolonged periods of disability and even death. Several uncontrolled studies have suggested a beneficial effect of intravenous immunoglobulin.

To review systematically the evidence from randomised controlled trials concerning the efficacy and safety of intravenous immunoglobulin in chronic inflammatory demyelinating polyradiculoneuropathy.

We used the Search Strategy of the Cochrane Neuromuscular Disease Review Group to search the Disease Group register and other databases for randomised controlled trials from 1985 onwards.

Randomised controlled studies examining the effects of any dose of intravenous immunoglobulin versus placebo, plasma exchange or corticosteroids in patients with definite or probable chronic inflammatory demyelinating polyradiculoneuropathy. Outcome measures had to include one of the following: a disability score, the Medical Research Council sum score, electrophysiological data or walking distance. Studies which reported the frequency of adverse effects were used to assess the safety of treatment.

Two reviewers independently reviewed literature searches to identify potentially relevant trials, scored their quality and extracted data independently. For dichotomous data, we calculated relative risks, and for continuous data, effect sizes (for definition see statistical analysis section) and weighted pooled effect sizes. Statistical uncertainty was expressed in 95% confidence intervals. Sensitivity analysis excluding studies with quality scores below A 0.50 and below B 0.75 was planned but not performed as all studies had quality scores above 0.75.

Six randomised controlled trials were considered eligible including 170 patients. Four studies on 113 patients compared intravenous immunoglobulin against placebo. One trial with 17 patients compared intravenous immunoglobulin with plasma exchange in a cross-over design and one trial compared intravenous immunoglobulin with prednisolone in 32 patients. A significantly higher proportion of patients improved in disability within one month after the onset of intravenous immunoglobulin treatment as compared with placebo (relative risk 3.17, 95% confidence interval 1.74 to 5.75). Whether all these improvements are equally clinically relevant cannot be deduced from this analysis because each trial used a different disability scale with a unique definition of a significant improvement. To overcome this problem an attempt was made to transform the various disability scales to the modified Rankin score. In three trials including 87 patients this transformation could be carried out. A significantly higher proportion of patients improved one point after intravenous immunoglobulin treatment compared to placebo (relative risk 2.47, 95% confidence interval 1.02 to 6.01). The effect size for change of mean disability score at six weeks comparing intravenous immunoglobulin with plasma exchange revealed no difference between the two therapies (effect size -0.07, 95% confidence interval -0.76 to 0.63.) The proportion of patients with a significant improvement did not differ significantly between prednisolone and intravenous immunoglobulin (relative risk of 0.91 (95% CI 0.50 to 1.68). Also, no difference in mean improvement on the disability scale was found at two weeks (effect size -0.12, 95% confidence interval -0.68 to 0.45) or six weeks (effect size -0.07, 95% confidence interval -0.63 to 0.50) between prednisolone and intravenous immunoglobulin. There were no statistically significant differences in frequencies of side effects between the three types of treatment.

The evidence from randomised controlled trials shows that intravenous immunoglobulin improves disability for at least two to six weeks compared with placebo, with a number needed to treat of three. During this period it has similar efficacy to plasma exchange and oral prednisolone. Since intravenous immunoglobulin, plasma exchange and prednisolone seem to be equally effective, it is currently uncertain which of these treatments should be the first choice. Cost, side effects, duration of treatment, dependency on regular hospital visits and ease of administration all have to be considered before such a decision can be made.