Effect of high-dose intravenous immunoglobulin on serum chemistry, hematology, and lymphocyte subpopulations: assessments based on controlled treatment trials in patients with neurological diseases.

The effect of intravenous immunoglobulin (IVIG) on various laboratory values was measured immediately before and after completion of serial monthly infusions of IVIG (2 g/kg) or an equal volume of placebo over 3-12 months, in 46 patients with neuromuscular diseases participating in controlled trials. Hematological, lymphocyte subpopulation, and chemistry values were analyzed and compared. After IVIG, but not placebo, a 34% reduction in lymphocytes was noted in 44/46 patients with a selective reduction of the T cells, but not the B or IL2R-positive cells. Counts returned to baseline within 30 days. Creatine kinase levels decreased by 23% and sedimentation rate increased by 275% after IVIG infusion. A nondilutional, artifactual, hyponatremia and hypomagnesemia was noted with IVIG but not placebo. We conclude that IVIG affects a variety of serum chemistry and hematological values either directly or artifactually by interfering with the laboratory method used for the assays. Transient lymphopenia is consistently seen, and may play a role in the immunomodulating effect of IVIG.