For example, a patients Ig value may be evaluated as low when using one reference system, while it would be considered normal according to another reference system. This inconsistency between reference systems can lead to unnecessary advanced testing and a greater financial burden on the patient. this study, we found that the rates of low Ig level in a group of pediatric patients differed significantly when evaluated using three different reference systems for age-related serum Ig levels Keywords:Children, reference system, serum immunoglobulin levels == 1. Introduction == Primary immunodeficiencies are inherited immune system disorders that cause increased frequency and severity of infections and predisposition to autoimmune disease and malignancies. They occur at a rate of 1 1:2000 at live births (1). The most common group of primary immunodeficiencies are the primary antibody deficiencies, which cause disorders in antibody production and function (2,3). Evaluation of patients with antibody deficiency should include B-lymphocyte count, serum total immunoglobulin (Ig) level measurement, and assessment of specific antibodies against protein and polysaccharide antigens (4). Maturation of the immune system and Ig levels begins in the neonatal period and continues into childhood. BMT-145027 BMT-145027 In healthy newborns, the serum IgG level matches that of the mother due to placental transfer in the last trimester; however, this level falls around 46 months after birth, then gradually increases again to adult level by the age of 5 or 6 years. IgA and IgM levels are very low in the neonatal period due to lack of encounters with foreign antigens. IgM reaches adult levels at about one year of age, while IgA reaches adult levels during adolescence. These processes result in age-related differences in Ig levels (4). In addition to age, genetic and environmental factors (frequent and/or prolonged antigenic stimulation) also affect Ig levels. Therefore, age-related reference intervals of healthy individuals in the population must be used when evaluating a patients Ig levels (5). An important problem in the determination of reference intervals is that these values vary by region and source population, as well as with laboratory and technical conditions. The International Federation of Clinical Chemistry (IFCC) recommends that each laboratory determine its own values (6). Immunological methods such as radial immunodiffusion, enzyme-linked immunosorbent assay (ELISA), and immunonephelometry have been used to measure IgG and IgG subgroups. The sensitivity of the method also influences reference values. Furthermore, differences in calibration between methods pose a major challenge in the comparison of reference intervals. For this reason, calibration based on an international reference material is recommended (7). The aim of the present study was to classify the results of Ig level measurements requested in the pediatric units of our hospital for various reasons as low or normal for the patients age using two different reference systems used in Turkey (5,8) and a reference system used in the US (9) and to determine whether the three systems yielded different proportions of patients evaluated as having low and normal Ig levels. == 2. Materials and methods == == 2.1. Patient population == Patients who underwent Ig testing in the outpatient and inpatient units of the Ankara Childrens Health and Diseases Hematology Oncology Training and Research Hospital of the Department of Health Sciences University between January 2010 and January 2016 were included. All patient data were obtained from their medical records and from the hospital database. The study was approved by the local Mouse monoclonal to CD105 ethics committee (2018-046). == 2.2. Measurement of serum immunoglobulin levels == Immunoglobulin measurements were performed with an IMMAGE 800 Immunochemistry System using the nephelometric method and values were expressed as mg/dL. == 2.3. Classification of low/normal immunoglobulin levels according to age == The patients Ig values were classified as low or normal according BMT-145027 to the relevant age-related reference intervals for each Ig value. For these reference intervals, we used two reference systems (5,8) based on age-related normal Ig ranges determined in Turkish children, and one reference system used in the United States (9). The percentage of patients with low and normal Ig levels in each age group was determined for each of the three references. == 2.4. Statistical analysis == Statistical analysis of the data was done with the SPSS for Windows version 22 software package. Categorical variables were expressed as number and percentage, continuous variables as minimummaximum, mean standard deviation, and median. Chi-square test was used to compare continuous variables between two independent groups. A P-value <0.05 was considered statistically significant. == 3. Results == A total of 20,138 patients (57.6% male) were included in the study. The median age of the patients was 55.7 months (interquartile range: 23.196.7 months)..