A recently published meta-analysis using more than 20 studies with nearly 1400 patients showed that subcutaneous immunoglobulin (SCIG) provides a more feasible alternative for treating chronic demyelinating polyneuropathy (CDIP) than intravenous immunoglobulin (IVIG). Overall, SCIG showed more considerable cost reductions over time, was more preferred by patients, and demonstrated comparable, and sometimes superior, health outcomes.1

Published in Neurological Sciences, the systematic review comprised 50 studies up till 2024, with 22 involved in the meta-analysis. Included studies offered clinical data on patients with CIDP, mostly from western Europe and the US, representing nearly 10% of their entire CIDP populations. Almost all studies included considered SCIG to be a maintenance therapy in their context, and thus, the primary goal of those studies was to reduce relapse rate and sustain or enhance neuromuscular functions.

Led by Mostafa Ramzi Shiha, of Cairo University, meta-analysis showed that SCIG significantly improved muscle strength and sensory function, had fewer and milder adverse events (AEs), reduced relapse rates, and received a strong preference. On muscle strength, a collection of 18 studies comprising 542 individuals with CIDP demonstrated a significant improvement in muscle strength post-SCIG treatment. Overall, the pooled standardized mean difference in Medical Research Council Scale (MRC) scores was 0.68 points (95% CI, 0.28-1.08), with statistically significant enhancement (P = .0008).

When evaluating muscle strength by dose level, results showed that the high dose subgroup showed a significant effect (SMD, 2.39; 95% CI, 0.79-3.98) and high heterogeneity (I2 = 95%), whereas there was no significant effect in the low dose subgroup (SMD, 0.05; 95% CI, 0.22 to 0.14). The medium dose subgroup showed a small but not statistically significant effect (SMD, 0.18; 95% CI, 0.04 to 0.40).

Overall, treatment with SCIG was associated with a 22% decreased risk of AEs compared with IVIG (P <.0001). An analysis of 2 studies found a significant difference in headache occurrence in the SCIG group (OR, 0.14; 95% CI, 0.07-0.30; P <.0001). Infusion site reactions, a concern for subcutaneous treatments, were not significantly more common with SCIG in 2 studies, with an OR of 1.75 (P = .50). In addition, there was no significant between-group differences in severe AEs as well (OR, 0.23; P =.19).

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As to why SCIG leads to fewer AEs relative to IVIG, investigators attributed this to the "slower absorption into the bloodstream with SCIG, which avoids the high peak levels of immunoglobulin G seen after IVIG administrations."

The Inflammatory Neuropathy Cause and Treatment (INCAT) disability score, developed in 2001, was used as an assessment for overall function and disability. Across 5 studies with available data comprising 67 patients, treatment with SCIG led to a significant improvement in sensory function as measured by INCAT Sensory Score. The pooled mean difference showed a reduction of 1.73 points (95% CI, 2.29 to 1.17), which was statistically significant (P <.00001). This improvement indicated enhanced sensory function following SCIG therapy.

On INCAT results, there was high heterogeneity (I2 = 92%) among the included studies. "For impaired functional mobility, no worsening was observed in the analysis of 9-hole peg test and timed meter walk test scores, indicating that patients preserved their functional mobility upon SCIG maintenance treatment, Shiha et al wrote.

In terms of relapse rate reduction, patients with CIDP treated with SCIG had significant reductions observed, with a risk ratio of 0.146 (95% CI, 0.090-0.202; P <.001) across 8 included studies. In comparison with conventional IVIG treatment, a previous 52-week open-label study found that IVIG administered as maintenance therapy resulted in a relapse rate of 10.5%, similar to the results of high-dose SCIG treatment in the 48-week, open-label PATH extension trial relapse rate of 10.8%. Overall, the findings from the meta-analysis indicated that both IVIG and SCIG might have comparable efficacy in terms of relapse rates.

Quality of life and health status also remained stable after treatment with SCIG, which was consistent with IVIG treatments. Interestingly, 2 included studies that used a more IgG treatment oriented scale like LQI that considers many items related to patients convenience, comfort, and independence, according to the IgG route of administration, showed better quality of life measures after SCIG. In addition, patients treatment preferences, when analyzed, unanimously demonstrated a preference for SCIG across all studies.

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Subcutaneous Immunoglobulin Shows Superiority Over IVIG in Treating CIDP, Meta-Analysis Shows - Neurology Live