From the Journals

Low IgG levels in COPD patients linked to increased risk of hospitalization



Among patients with COPD, the presence of hypogammaglobulinemia confers a nearly 30% increased risk of hospitalization, results from a pooled analysis of four studies showed.

“Mechanistic studies are still warranted to better elucidate how IgG and other immunoglobulins, in particular IgA, may contribute to the local airway host defense,” researchers led by Fernando Sergio Leitao Filho, MD, PhD, wrote in a study published in Chest (2020 May 18. doi: 10.1016/j.chest.2020.04.058). “Nevertheless, our results raise the possibility that, in select COPD patients, IgG replacement therapy may be effective in reducing the risk of COPD hospitalizations. Given the growing rate of COPD hospitalization in the U.S. and elsewhere, there is a pressing need for a large well-designed trial to test this hypothesis.”

In an effort to evaluate the effect of IgG levels on the cumulative incidence of COPD hospitalizations, Dr. Leitao Filho, of the University of British Columbia, Vancouver, and colleagues drew from 2,259 patients who participated in four different trials: Azithromycin for Prevention of Exacerbations of COPD (MACRO), Simvastatin for the Prevention of Exacerbations in Moderate and Severe COPD (STATCOPE), the Long-Term Oxygen Treatment Trial (LOTT), and COPD Activity: Serotonin Transporter, Cytokines and Depression (CASCADE). The mean baseline age of study participants was 66 years, and 641 (28.4%) had hypogammaglobulinemia, which was defined as having a serum IgG levels of less than 7.0 g/L, while the remainder had normal IgG levels.

The pooled meta-analysis, which is believed to be the largest of its kind, revealed that the presence of hypogammaglobulinemia was associated with an incidence of COPD hospitalizations that was 1.29-fold higher than that observed among participants who had normal IgG levels (P = .01). The incidence was even higher among patients with prior COPD admissions (pooled subdistribution hazard ratio, 1.58; P < .01), yet the risk of COPD admissions was similar between IgG groups in patients with no prior hospitalizations (pooled SHR, 1.15; P = .34). Patients with hypogammaglobulinemia also showed significantly higher rates of COPD hospitalizations per person-year, compared with their counterparts who had normal IgG levels (0.48 vs. 0.29, respectively; P < .001.)

The authors acknowledged certain limitations of the study, including the fact that they measured serum IgG levels only at baseline “when participants were clinically stable; thus, the variability of IgG levels in a given individual over time and during the course of an AECOPD [severe acute exacerbation of COPD] is uncertain. Secondly, clinical data on corticosteroid use (formulations, dose, and length of use) were not readily available. However, systemic steroid use (one or more courses due to AECOPD prior to study entry) was accounted for in our analyses.”

The MACRO, STATCOPE, LOTT trials, and the CASCADE cohort were supported by the National Heart, Lung, and Blood Institute; National Institutes of Health; and Department of Health & Human Services. The current study was funded by the Canadian Institutes of Health Research and BC Lung Association. The authors reported having no relevant disclosures.

SOURCE: Leitao Filho SF et al. Chest. 2020 May 18. doi: 10.1016/j.chest.2020.04.058.

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