Comparison of two agglutination methods for detection of anti-Brucella antibodies in blood bank donors.

Abstract

Introduction: One of the screening tests performed in blood bank donors is the determination of anti-Brucella antibodies. The present study proposes the use of the Rose Bengal test to replace the Febrile Antigens test. Objectives: i) To evaluate the interobserver agreement for the Rose Bengal technique and the inter-assay agreement between both techniques. ii) To estimate the sample proportion of reactive donors with either technique between two different periods. Materials and Methods: Observational, cross-sectional, retrospective study. The results of patients who attended the Hemotherapy Service of the National “Profesor Alejandro Posadas” Hospital (Buenos Aires, Argentina) from November 1st 2019 to August 18th 2021 were evaluated. Both interobserver and interassay agreement were evaluated with Cohen’s Kappa test. The proportions of reactive donors of each period were contrasted through the twoproportion comparison test. Results: The interobserver agreement showed a Kappa of 0.78 (95%CI: 0.61 - 0.95), whereas the interassay agreement showed a Kappa of 0.29 (95% CI: 0.15 - 0.43). The proportion of reactive donors was 4.0% for the Febrile antigen period and 1.6% for the Rose Bengal period. Conclusions: An acceptable qualitative agreement was observed between both observers, but not between both techniques. The difference in proportions between reactive donors of each period was highly significant. The change in methodology allowed increasing the specificity without decreasing the sensitivity. The use of the Rose Bengal test reduced the discard of blood units.