A Higher IgG Trough Level May Reduce Risk of Pneumonia in PIDD Patients on IVIG Therapy

The pre-infusion trough levels of IgG required to minimize infection risk in IVIG-treated patients with primary immunodeficiency disease (PIDD) remains uncertain. To address this question, U.S. investigators identified and quantitatively combined all available studies evaluating IgG trough levels and pneumonia incidence in PIDD patients receiving IVIG replacement therapy for hypogammaglobulinemia.

Seventeen studies published between 1982 and 2009, totaling 676 patients and 2,127 patient-years of follow-up, were included in this meta-analysis. Pneumonia incidence declined by 27 percent with each 100 mg/dL increment in trough IgG (incidence rate ratio, 0.726; 95 percent confidence interval, 0.658- 0.801). The incidence of pneumonia with maintenance of a 500 mg/dL IgG trough level (0.113 cases per patient-year) was fivefold higher than a trough level of 1,000 mg/dL (0.023 cases per patient-year).

While a 500 mg/dL emerged from early studies as an appropriate initial minimum IgG trough target, subsequent clinical evidence has prompted recommendations for higher targets, generally to levels near or above the lower limit of IgG concentration (about 700 mg/dL) in normal healthy adults. The authors concluded that their findings offer evidence that pneumonia risk can be progressively reduced by higher trough IgG levels up to at least 1,000 mg/dL.