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

PURPOSE Correlations between the i.v. immune globulin (IVIG) dose and the change in serum immunoglobulin G (IgG) concentration with three methods of weight-based dosing were investigated. METHODS A retrospective medical records review was conducted to identify patients in a multicenter healthcare system who received IVIG over a 10-year period and had serum IgG measurements within two days before and two days after the date of IVIG administration. For each of the 11 adults and 7 adolescents identified, the relationship between the weight-based dose of IVIG (determined using actual body weight [BW], adjusted BW, or ideal BW [IBW]) and the resulting change in serum IgG was evaluated. Correlation coefficients and corresponding p values for the three dosing methods were calculated and compared. RESULTS Among adult patients, the correlation of IVIG dose and postdose change in serum IgG was strongest with dosing by IBW (correlation coefficient [r], 0.83 [p < 0.05] versus r values of 0.73 and 0.70 for dosing by adjusted BW or actual BW, respectively [p = 0.05 for both]); the corresponding r values in adolescent patients were 0.99, 0.99, and 0.95, respectively (p < 0.005 for all). There were no statistically significant differences between the r values calculated for the three weight-based dosing methods in either adults or adolescents. CONCLUSION In adult patients, the correlation between the dose of IVIG and the change in IgG level was strongest when doses were calculated using IBW; comparable degrees of correlation were observed with the three evaluated methods of weight-based dosing in the adolescent population.