Effect of hypoimmunoglobulinemia on laboratory evaluation of multiple sclerosis

A female patient with Crohn's disease was assessed by laboratory evaluation for multiple sclerosis. Because of her hypoproteinemia, she was given an albumin infusion, which caused immunoglobulin concentrations to fall below the normal limit. Based on a cerebrospinal fluid (CSF) sample drawn after infusion, she was found to have an abnormally high IgG index and a high intrathecal IgG synthesis rate. However, clinical correlations ruled out demyelinating disease. Various equations used for the calculation were examined and found to yield false positive results with values of serum IgG below the reference range. Only the Ohman formula provided the correct prediction in this patient. Although hypo- or hyper-albuminemia have little effect on these equations, they may escalate the impact of hypoimmunoglobulinemia. Thus, interpretation of laboratory data under these conditions must be exercised with care.