Patient selection
This methodological study was conducted in Istanbul University, Faculty of Medicine, Adult Immunology and Allergy Clinic. To be included in the study, all of the following inclusion criteria had to be fulfilled: >18 years, diagnosis of CVID more than 6 months, currently receiving intravenous or subcutaneous immunoglobulin replacement therapy. CVID was diagnosed according to the ESID criteria23. Inability or unwillingness to give informed consent and significant medical or psychiatric illness were the exclusion criteria.