A Novel Approach for Antibody Level Assessment: Integrating Titre and Cumulative Grading for Improved Assessment

Abstract

Background: Assessing the antibody titres is an essential aspect of Immunohaematology. However, traditional methods of antibody quantification depend only on the determination of the titre; highest dilution that exhibits agglutination, which might not adequately represent the total antibody load. Cumulative grading was calculated by adding individual grading from all dilutions and it considers all reactions in the dilution series. This study proposed a derived parameter by combining titre and its corresponding cumulative grading to offer a thorough evaluation of antibody levels. Objectives: To propose and derive parameters that integrate titre and its corresponding cumulative grading for a more precise measurement of IgM and IgG isotypes of anti-A and anti-B antibody levels in donors with blood group O Methods: A laboratory-based, experimental, cross-sectional study was conducted involving 200 donors with blood group O, at the Department of Transfusion Medicine, University Hospital of General Sir John Kotelawala Defence University. Antibody titres (IgM and IgG anti-A and anti-B) were measured using the conventional tube method with serial two-fold dilutions, and the strength of agglutination was graded and the cumulative grading was calculated. Four parameters were proposed and derived integrating titre and cumulative grading; ‘Log₁₀(Titre)×Cumulative Grading’, ‘Log₁₀(Titre)/ Cumulative Grading,‘Titre×Cumulative Grading’, and ‘Titre/ Cumulative Grading’. Spearman correlation analysis was conducted to examine the relationship between the antibody titre and their corresponding cumulative grading and proposed derived parameters. Results: All antibody titres revealed strong positive correlations with their corresponding cumulative grading (IgM anti-A rs=0.866; p<0.01, IgG anti-A rs=0.900; p<0.01, IgM anti-B rs=0.891; p<0.01, IgG anti-B rs=0.865; p<0.01). Among four proposed derived parameters, ‘Titre ×Cumulative Grading’ exhibited the highest correlation with its corresponding antibody titre for all antibody types (IgM anti-A rs=0.976; p<0.01, IgG anti-A rs=0.987; p<0.01, IgM anti-B rs=0.977; p<0.01, IgG anti-B rs=0.984; p<0.01), establishing it as the most reliable proposed derived parameter for measuring antibody levels. Conclusions: The ‘Titre×Cumulative Grading’ parameter better quantifies antibody levels than the titre alone by integrating the cumulative grading. Applying this in blood bank settings could improve decision-making in transfusion medicine and newborn care by identifying patients at risk of severe antibody-mediated reactions even when titres appear low or borderline.