Immunoglobulin Prophylaxis

Multiple studies have shown some reduction in infectious complications among patients with hypo IgG who received IVIG, but all the studies (including randomized trials) included less than 100 patients. In the largest trial, patients with IgG concentrations less than 50% of normal who had at least one serious infection were randomized to receive 400 mg/kg IVIG or normal saline every 3 wk for 1 yr (74). Moderately severe bacterial infections were reduced by 50%, but there was no effect on the occurrence of viral and fungal infections, and the proportion of patients remaining free of infection was the same in both groups. A cost-effectiveness analysis of this study concluded that IVIG does not increase the quality or length of life and is not cost-effective (75). A subset of patients from this trial then continued in a double-blind crossover study (76). Serious bacterial infections were significantly less frequent in the months during which patients received IVIG and in patients whose IgG concentrations were maintained above 6.49 mg/dL.

Because of the significant cost of IVIG, several studies have examined lower dose therapy. The administration of 10 g IVIG every 3 wk eventually led to normal IgG concentrations after 11 doses (77). Febrile episodes were reduced by 50%, and hospital admissions for infection were reduced from 16 to 5. In another study, 30 evaluable patients were given IVIG 300 mg/kg every 4 wk for 6 mo and then changed to no IVIG (78). There were 67% of patients with no infection during the period of IVIG administration vs 30% during the period of no therapy. The number of serious infections per year was reduced by 50% during IVIG therapy. In another study, patients were randomized to IVIG 500 mg/kg every 4 wk or to 250 mg/kg every 4 wk (79). There were no apparent differences in infectious complications between the two regimens. A recent study compared a higher dose with conventional replacement therapy in patients with primary hypo GG (80). Patients were randomly assigned to IVIG 600 mg/kg or 300 mg/kg every 4 wk (adults) for 9 mo, and then to the alternate dosage schedule. There were a median of 2.5 infections/patient during high-dose therapy vs 3.5 during low-dose therapy. The median numbers of severe infections were 1.2 vs 1.5. Also, the median duration of respiratory infections was longer during low-dose therapy (29 vs 22 d).

There are several problems with the use of IVIG. These preparations do not correct deficiencies in IgM and IgA, which also play a role in protecting against infections. Weeks et al. (75) concluded that 1 quality-adjusted life-year achieved per patient costs $6 million without any increase in life expectancy. Hence, while IVIG replacement reduces the frequency of infec tions, it is not cost-effective and should be reserved only for selected patients who have recurrent severe bacterial infections and IgG concentrations less than 400 mg/dL. In addition, therapy with IVIG is not likely to be useful for preventing viral or fungal infections. Also, the optimum dose of IVIG has not been determined.

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