Immunoglobulin G—IgG—antibody molecule

Patients with chronic lymphoblastic leukemia (CLL) and non-Hodgkin lymphoma (NHL) were less likely to experience severe infection if they received frequent testing for immunoglobulin G (IgG)—proteins in the immune system that are at low levels in patients with these blood cancers.

The new research, published today in the journal Blood Advances, showed immunoglobulin replacement therapy (IgRT) reduced both recurrent infections and severe infections in patients enrolled in the study and could possibly save patients’ lives. Currently roughly half of all CCL patients and one-third of NHL patients die from complications caused by infections.

“This is the first large, real-world study to examine current practices in IgG testing and the use of IgRT among patients with CLL and NHL,” said  lead investigator Jacob D. Soumerai, MD, assistant professor of medicine at the Massachusetts General Hospital Cancer Center and the Harvard Medical School. “Our most striking finding is that real-world practice is highly variable. We found that many patients are not tested for IgG deficiency, and IgRT is often not given despite the development of recurrent infections.”

The new research findings come from a retrospective analysis of more than 17,000 de-identified patient medical records of adult patients treated for CLL (3,920) and NHL (13,232) contained in the the Mass General Brigham Research Patient Data Registry. The average patient age was 66 with 58% of patients male and 90% of patients white. IgG testing was given to 51.2% of NHL patients and 67% of CLL patients. IgRT was provided to 4.7% of NHL patients and 6.5% of CLL patients.

For patients who received at least one IgG test, the researchers compared IgG blood levels, the proportion of patients with IgG levels that were deemed low (less than 500mg/DL), infection rates, and the use of antimicrobial medications at three, six, and 12 months before and after the patient’s first IgRT treatment.

The data showed that immunoglobulin testing significantly lowered the risk of a patient subsequently developing a severe infection. The odds of CLL and NHL patients who had three or more previous IgG tests were 92% and 82% lower odds, respectively, of later developing a severe infection.

“Within each disease cohort, patients with three or more IgG tests were more likely to have low IgG detected and also more likely to receive IgRT,” said Soumerai. “These findings suggest that patients known to have low levels of IgG might be more likely to communicate recurrent minor infections to their hematologists, leading to improved IgRT use.”

Treatment guidelines from different medical societies do recommend IgG testing, but the recommendations vary significantly regarding when to provide the testing to patients and how often. There is also broad variance in the testing practices of hematologists who care for these patients as evidenced by the data used in the study which showed half did not receive IgG testing at all. The evidence from this study demonstrates the urgent need for developing consensus best practices for both IgG testing and IgRT, Soumerai noted.

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