Retrospective Study of Spirometry in CVID Reveals that FEF25%-75% Can Be Used to Guide the Dose of IgG Used to Protect Pulmonary Function

RATIONALE: IgG therapy protects against lung function decline from bronchial infections in CVID. We tested whether increasing IgG dosage was beneficial in patients who exhibited a decline in forced_expiratory_flow at 25%–75% (FEF25%–75%).

METHODS: Of 193 CVID patients seen over 12 years; 57 were seen on ≥3 visits, demonstrated a ≥10% decrease in FEF25%–75% on visit 2, and met inclusion/exclusion criteria. Three FEF25%-75% tiers were identified: top (>80% of predicted), middle (50%-80%), and bottom (<50%). FEF25%–75%, forced_expiratory_flow at one second (FEV1), forced_vital_capacity (FVC), and FEV1/FVC at visit 3 were compared among those treated or not treated (controls) with additional IgG.

RESULTS: Treated and controls did not differ in antibiotic usage or reports of clinical infections. Visit 3 FEF25%-75% increased among treated middle tier (11.8±3.3%, p=0.0030; tested by mixed model), but not controls (0.3±2.9%, p=0.94). In top tier, FE25%-75% increased in treated (8.4±4.4%, p=0.08) and controls (10.2±4.2%, p=0.14). In bottom tier, FE25%-75% decreased slightly in treated (-1.0±2.6%, p=0.68), but increased in controls (5.1±2.0%, p=0.02). Improvement in FEV1/FVC at visit 3 was significant among middle tier treated, but not controls (7.2±3.3%, p=0.04 vs. -0.2±0.8%, p=0.84).

CONCLUSIONS: Among CVID patients with moderate, presumed reversible, obstruction on numerically adequate IgG therapy; increasing IgG resulted in an increased FEF25%-75% and FEV1/FVC.