Is it necessary to add the eluate testing to the direct antiglobulin test to improve the detection of maternal erythrocyte alloantibodies?

BACKGROUND: The screening of umbilical cord blood samples by the Direct Antiglobulin Test (DAT) is the reference tool for the identification of maternal erythrocyte alloantibodies present in erythrocytes; however, its diagnostic usefulness is controversial. OBJECTIVE: To evaluate the diagnostic validity, safety, and efficiency of the eluate testing (detection of antibody in erythrocyte eluates by the Indirect Antiglobulin Test/IAT) in cord blood samples for detection of maternal erythrocyte alloantibodies in comparison with the DAT. MATERIALS AND METHODS: Evaluation study of diagnostic tests. DAT and eluate testing were performed in 306 cord blood samples from neonates born to mothers admitted at Clínica Somer in Rionegro, Colombia; then, antibodies present in the eluates were identified with erythrocyte panels. Percentage of positive results by DAT and IAT were compared with the Pearson's chi-square test and the agreement between both assays with the Cohen's kappa coefficient. The diagnostic sensitivity, specificity, safety, and efficiency of the eluate testing were calculated, taking into account the use of DAT as an imperfect reference test. RESULTS: The DAT detected alloantibodies in 6.21% of samples and the eluate testing in 14.1 %; the strength of agreement between both tests was moderate (k = 0.56) due to 25 discrepancies. The eluate testing showed sensitivity and specificity of 98.83 % and 92.31 % respectively, and a negative predictive value of 99.9 %. The diagnostic efficiency was sufficient for detection of maternal erythrocyte alloantibodies. The antibodies identified in the erythrocyte eluates were anti-A or anti-B (79.5 %), anti-D (136%), anti-C (2,3%), and anti-Fya (2,3%). CONCLUSION: The eluate testing in cord blood samples is a valid, safe, and efficient test for the diagnosis of maternal erythrocyte alloantibodies.

Immunohematological study of the first pediatric patient with the Bombay phenotype in Medellín, Colombia.

The Bombay (Oh) phenotype is a rare phenotype in which red blood cells lack the H antigen as a result of a point mutation in the H gene. Oh patients are a challenge in transfusion medicine. We present a case of a pediatric patient with the Bombay phenotype who was carried to the emergency department of the Hospital Universitario San Vicente Fundación in Medellín, Colombia. The patient presented gastrointestinal hemorrhage and required transfusion therapy. Pretransfusion and molecular immunohematological analyses identified the Bombay phenotype. The patient was transfused with Oh red blood cells imported to Colombia from the Hematology and Hemotherapy Center of Ceará (Hemoce) in Fortaleza, Brazil. This first case of an Oh individual in Colombia highlights the need to look for donors with rare phenotypes to fulfill the transfusion requirements of the population.