Serum Trough IgG level and Annual Intravenous Immunoglobulin Dose Are Not Related to Body Size in Patients on Regular Replacement Therapy

Abstract

Therapeutic regimens of intravenous immunoglobulin are currently based on actual body weight. The relationship between immunoglobulin dose and serum IgG level in relation to body size was retrospectively explored in patients on replacement therapy. Data were collected as part of a national audit on immunoglobulin therapy in patients with common variable immunodeficiency. 107 patients received immunoglobulin titrated to optimum effect. Correlations were sought between body mass index, trough IgG levels, infusion frequency and total annual dose. The mean (±SD) trough IgG level was 8.4±1.6 g/L and annual immunoglobulin dose received was 456.8±129.4 g. There was no relationship between annual dose and trough IgG level, regardless of infusion frequency, or adjustment for weight or body mass index. These results support the clinical practice of immunoglobulin prescription by clinical outcome rather than fixed dose by body weight. Future studies exploring immunoglobulin efficacy should include treatment arms with dosages based on both ideal and actual body weight, as ideal body weight-based prescribing would save significant amounts of product.

Subcutaneous immunoglobulin therapy: a new option for patients with primary immunodeficiency diseases

“…The effect of body mass index (BMI) on serum trough levels is unclear. In a retrospective review of 107 patients comparing the annual dose of IG and the serum trough IgG levels, no relationship was seen even after correction for BMI 52. However, Berger et al found that subjects with a BMI greater than 30 kg/m 2 required a greater dose adjustment for SCIG in order to match the AUC of IVIG 53.…”

Correlation of weight-based i.v. immune globulin doses with changes in serum immunoglobulin G levels

“…The theory of concentration-dependent catabolism offers an explanation for why, in previous studies, no correlation has been found between IgG trough levels and IVIG dosing but an association has been demonstrated between the IVIG dose and the change in serum IgG level. 10,12 Our study now reports a correlation between the weight-based dose and the change in serum IgG level.…”

“…A retrospective study published in 2011 evaluated the relationships of IgG trough level to annual IVIG dose, annual weight-based IVIG dose, and body mass index (BMI)-based annual IVIG dose. 10 The study authors concluded that doses adjusted for BW or BMI did not correlate with postdose serum IgG trough levels and that dosing by IBW instead would preserve IVIG resources and also reduce the cost of therapy without affecting trough level attainment. Additionally, a study of IVIG pharmacokinetics in pregnant women reported peak and four-week serum IgG trough levels for women who received doses of 0.5-1.0 g/kg.…”

Considerations for dosing immunoglobulin in obese patients

“…A UK‐based retrospective audit involving 107 CVID patients across four centres did not find any relationship between annual dose and trough level despite normalizing for weight and BMI . The lack of any association may indicate that the sample size and power of this study may have been too small to detect the positive correlation between change in plasma concentration and Ig dose, which has been demonstrated in a number of contemporary studies .…”