Calculated globulin is clinically useful as a screening test for
antibody deficiency in Turkish adult patients
Abstract
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.