Spirometry in the management of CVID

Common Variable Immunodeficiency (CVID) is a primary disorder of the immune system characterized by an inadequate ability to produce antibodies predisposing patients to infections, predominantly within the respiratory tract. The mainstay of treatment is supplemental immune globulin. These patients are typically managed by following serial serum IgG levels and the dose of immunoglobulin adjusted to maintain a level within the normal range. However, this measurement does not precisely reflect the physiological demand for IgG replacement and patients may be underdosed predisposing them to serious infections and developing long term sequela. Adult patients seen in a specialty adult immune deficiency clinic between 1999-2016 were evaluated for underlying immune deficiency and placed on supplemental immunoglobulin if appropriate. These patient were tested with spirometry at first visit and every subsequent evaluation. Analysis of records of these patients reveals that the FEF25-75 on spirometry correlates well with IgG levels and an increase in immunoglobulin dose corrects the FEF25-75 in predictable pattern. The FEF25-75 is reduced in patients with untreated or insufficiently treated CVID. This is possibly a result of underlying small airway inflammation. Our research shows that this value may be reflective of underlying infectious inflammation in the patient with CVID and a better marker of disease activity and successful treatment. Patients whose immunoglobulin dose was adjusted to improve small airway inflammation yielded overall better clinical outcomes.