Backgrounds: Heterogeneous clinical features of antibody deficiency (AD) may cause diagnostic delays. Calculated globulin (CG) (total protein minus albumin) has been proposed as a screening test to prevent morbidity due to diagnostic delays in AD. Our aim is to validate CG as a screening test in AD in Turkish adult patients by comparing its role with gamma globulin analysis in protein electrophoresis. Methods: Fifty serum samples were randomly collected for each level of CG from 1.5 to 2.5 mg/dl and tested for serum IgG, IgA, IgM levels and protein electrophoresis. Cut-off values predicting low IgG levels were calculated for electrophoretically determined gamma globulin and CG. Additionally, the data of 47 patients followed up in our clinic with a diagnosis of primary antibody deficiency (PAD) were retrospectively analyzed. Results: A total of 550 adult patients were included in the study. The CG value predicting patients with IgG <600 mg/dl as a screening test was determined as <2.0 with 83.8% sensitivity and 74.9% specificity. The gamma globulin value which predicted patients with the same IgG value of 89.0% sensitivity and 89.4% specificity was determined as <0.7. In the retrospective analysis, 37 of 47 patients (78.7%) with PAD had a CG value of <2.0 at the time of the diagnosis and all 13 patients (%100) whose gamma globulin values were measured at the time of the diagnosis had a gamma globulin value of <0.7. Conclusion: The determined CG cut-off value of <2.0 can be used as a screening test in Turkish adult patients.

Medical Algorithm: Diagnosis and Managemen of Humoral ImmunodeficienciesAnna Šedivá1, Tomáš Milota1, Jiří Litzman2, Isabella Quinti3, ESID Clinical Working Party, EAACI Primary Immunodeficiency Working Group, Stephen Jolles4Department of Immunology, 2nd Faculty of Medicine Charles University, V Uvalu, University Hospital in Motol, Prague, Czech RepublicFaculty of Medicine, Masaryk University Brno, Czech Republic; Department of Clinical Immunology and Allergology, St Anne´s University Hospital, Brno, Czech RepublicDepartment of Molecular Medicine, Sapienza University of Rome, Rome, ItalyImmunodeficiency Centre for Wales, University Hospital of Wales, Cardiff, UKFor ESID Clinical Working Party:Isabelle Meyts, Department of Pediatrics, Leuven University Hospitals, Leuven, BelgiumSiobhan Burns, Institute of Immunity and Transplantation, University College London, London, United Kingdom; Department of Immunology, Royal Free London NHS Foundation Trust, London, United KingdomAuthor´s contributions:AS prepared the concept and wrote the manuscript, TM edited Figures and wrote the manuscript, JL designed Figures and revised manuscript, IQ designed Figures and revised the manuscript, IM revised manuscript, SB revised manuscript, ST edited Figures and wrote the manuscript.