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.
