Serum IgG levels as biomarkers for optimizing IVIg therapy in CIDP.

Intravenous immunoglobulin (IVIg) is a proven effective treatment for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and Guillain-Barré syndrome (GBS). In GBS, patients show a large variability in serum immunoglobulin G (IgG) levels after standard IVIg treatment and a large increase in serum IgG levels (ΔIgG) was associated with a better outcome. Whether this is also the case in CIDP is not known. In contrast to GBS, most patients with CIDP need regular IVIg treatment for a prolonged period of time but the speed and magnitude of clinical response varies considerably between patients. Some patients with CIDP may need at least two IVIg courses before clinical signs of improvement become clear. At present, this clinical response is the only indicator used to adjust the IVIg dose and interval during maintenance treatment. Biomarkers reflecting disease activity or IVIg pharmacokinetics might be helpful to monitor patients and find the optimal dosage and frequency of IVIg treatment for individual patients. A recent prospective study in CIDP indicated that the increased ΔIgG after standard IVIg dosage during maintenance treatment was relatively constant within individual patients, but differed considerably between patients who were treated with the same stable dosage and interval of IVIg. Further studies are required to determine whether this variation in pharmacokinetics of IVIg is related with clinical recovery and whether IgG levels can be used as biomarkers to monitor and to adjust the optimal IVIg dosage in individual patients with CIDP.