Background: Hypogammaglobulinemia (serum IgG levels < 7.0 g/L) has been associated with increased risk of COPD exacerbations but has not yet been shown to predict hospitalizations. Research Question: To determine the relationship between hypogammaglobulinemia and the risk of hospitalization in patients with COPD. Study Design and Methods: Serum IgG levels were measured on baseline samples from four COPD cohorts (n = 2,259): Azithromycin for Prevention of AECOPD (MACRO, n = 976); Simvastatin in the Prevention of AECOPD (STATCOPE, n = 653), Long-Term Oxygen Treatment Trial (LOTT, n = 354), and COPD Activity: Serotonin Transporter, Cytokines and Depression (CASCADE, n = 276). IgG levels were determined by immunonephelometry (MACRO; STATCOPE) or mass spectrometry (LOTT; CASCADE). The effect of hypogammaglobulinemia on COPD hospitalization risk was evaluated using cumulative incidence functions for this outcome and deaths (competing risk). Fine-Gray models were performed to obtain adjusted subdistribution hazard ratios (SHR) related to IgG levels for each study and then combined using a meta-analysis. Rates of COPD hospitalizations per person-year were compared according to IgG status. Results: The overall frequency of hypogammaglobulinemia was 28.4%. Higher incidence estimates of COPD hospitalizations were observed among participants with low IgG levels compared with those with normal levels (Gray's test, P < .001); pooled SHR (meta-analysis) was 1.29 (95% CI, 1.06-1.56, P = .01). Among patients with prior COPD admissions (n = 757), the pooled SHR increased to 1.58 (95% CI, 1.20-2.07, P < .01). The risk of COPD admissions, however, was similar between IgG groups in patients with no prior hospitalizations: pooled SHR = 1.15 (95% CI, 0.86-1.52, P =.34). The hypogammaglobulinemia group also showed significantly higher rates of COPD hospitalizations per person-year: 0.48 ± 2.01 vs 0.29 ± 0.83, P < .001. Interpretation: Hypogammaglobulinemia is associated with a higher risk of COPD hospital admissions.
Bibliographical noteFunding Information:
FUNDING/SUPPORT: The MACRO, STATCOPE, LOTT trials and CASCADE cohort were supported by the National Heart, Lung, and Blood Institute, National Institutes of Health, and the Department of Health and Human Services. The current study was funded by the Canadian Institutes of Health Research (CIHR) and BC Lung Association. D. D. S. holds a De Lazzari Family Chair at the UBC Centre for Heart Lung Innovation (HLI) and is a Tier 1 Canada Research Chair in COPD. R. M. R. is supported in part by the Flight Attendant Medical Research Institute (FAMRI).
- immunoglobulin G
PubMed: MeSH publication types
- Journal Article