LifeShare Blood Center Shreveport, Louisiana, United States
Background/Case Studies: A 46 yr. old African American female with sickle cell disease was referred to the Immunohematology Reference Laboratory for antibody identification. Anti-C, -E, -Fya, -Jkb and anti-U were identified. Weak non-specific reactivity was noted with phenotypically similar cells. The auto-control and DAT were negative. The patient was transfused one month prior and a possible transfusion reaction was noted at that time. A Monocyte Monolayer Assay (MMA) was ordered to assess the clinical significance of the anti-U and the nonspecific, unidentified antibody.
Study
Design/Methods: Serologic evaluation included tube testing with Gamma N-HanceTM (Immucor, Inc, Norcross, GA) using EDTA samples. The MMA was performed according to published methods.RBCs from six donors known to be C- E- K- Fy(a-) Jk(b-) U+ were selected to challenge the significance of the anti-U. P</span>atient serum plus the addition of fresh complement (fresh serum) was used to perform the MMA. The MI (monocyte index), the percentage of RBCs adhered and/or ingested vs free monocytes, was calculated to predict clinical significance.
Results/Findings: Two distinct sets of results were observed in the MMA. One demonstrated minimal reactivity with anti-IgG and minimal risk of clinical significance. The other showed significantly stronger reactivity with anti-IgG and anti-C3 and a high risk of clinical significance. See table 1 for a summary of findings. Additional antigen typing of the donor cells found those with low MI values were Le(b-) and those with high MI values were Le(b+). Repeat serology using plasma with the addition of fresh complement demonstrated invitrohemolysis at 37C with the Le(b+) cells. No hemolysis and markedly weaker reactivity at AHG was detected using plasma only. The serum sample demonstrated hemolysis at 37C with and without the addition of fresh complement. These results indicate the anti-Leb binds complement, is clinically significant and has the potential to cause an overt hemolytic transfusion reaction. Conclusions: Automation in transfusion medicine has tremendous value. However, with implementation of these methodologies, sample collection has transitioned from serum to plasma. Since anticoagulants in plasma inhibit complement activation, this may lead to erroneous results of antibody detection testing in the presence of complement-dependent antibodies. Since the preferred sample for the MMA is serum, and fresh complement is added, the hemolytic anti-Leb was readily detected. Failure to identify complement-dependent antibodies in pre-transfusion testing is a significant risk when plasma is used rather than serum.
