Patient Recruitment and Study Design
The study was initiated after obtaining ethics committee approval
(2019/1455) from the ethics committee of Istanbul University, Istanbul
Faculty of Medicine. Patients were recruited from all adult patient
clinics in Istanbul Faculty of Medicine Hospital which is the biggest
tertiary university hospital in Istanbul, following approval from heads
of departments. A simple application of computation which automatically
subtracts serum albumin from serum total protein level was integrated to
the hospital computer operating system. It computes the CG value in all
patients whose serum total protein and albumin levels were measured due
to any reason in the central biochemistry laboratory. Technicians
working in the biochemistry laboratory informed the Immunology and
Allergic Diseases Division daily about all the patients with a CG value
between 1.5-2.5 g/dL for further evaluation. The patients were given
detailed information about the study by phone and asked if they wished
to become a study participant. Patients who agreed to participate in the
study and signed the written informed consent forms were invited to the
Immunology and Allergic Diseases outpatient clinic to provide further
clinical information. Inpatients who gave consent to participate in the
study were visited on the wards. Patients who did not give informed
consent, those on intravenous fluids replacement and those under the age
of 18 were excluded from the study. Further analyses of IgG, IgM, IgA
levels and protein electrophoresis were performed on the study
participants’ remaining serum samples which were kept in the
biochemistry laboratory. If there were no remaining suitable serum
samples for further analysis, patients were asked for donation of venous
blood samples. The patients who did not have remaining suitable serum
samples and did not want to donate serum samples were excluded from the
study.
Fifty patients were planned to be included for each level of CG at 1.5,
1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4 and 2.5 g/dL. Therefore, in
order to reach 550 volunteers, 686 patients were interviewed. Since 82
of these patients did not give informed consent after receiving detailed
study information, they were excluded. Fifty-four patients were also
excluded from the study since their blood samples were unsuitable for
laboratory tests (Figure 1).
Age, gender and clinical features, comprising of clinics which follow-up
the patients, current diseases, drugs used, frequency of antibiotic use,
need for parenteral antibiotics, infections in the medical history and
infection frequency of the total 550 patients were recorded in the
assessment forms.