Red cell survival studies in a patient with anti-Tca

Successful transfusion of antigen positive blood to alloimmunised patients using a monocyte monolayer assay

BACKGROUND

Providing adequate transfusion support for alloimmunised patients for whom antigen negative blood is not readily available is hampered by the risk of a haemolytic reaction. The monocyte monolayer assay (MMA) has shown good correlation between the antibody clinical significance and the fate of antigen positive blood.

MATERIALS AND METHODS

From 2006 to 2013, the clinical significance of red cell alloantibodies produced by 61 patients was evaluated using a MMA; and antigen positive blood offering the best survival advantage was selected for transfusion following a secondary MMA crossmatch. Post-transfusion, patients were evaluated for clinical signs of haemolysis.

RESULTS

Overall, 19 of 61 (31·1%) of our antibodies were potentially clinically significant, with a monocyte index (MI) > 5%. There was no correlation between the clinical significance as showed by the MMA, and the specificity of the antibody or the strength of reactivity at antihuman globulin (AHG) phase. Using the MMA as a secondary crossmatch method, 31 alloimmunised patients (including: eight anti-hr(B), four anti-Yt(a), one each anti-Rg1, -Co(a), Er(a), Le(b), -LW, -Sl1) received 103 antigen positive blood units with no clinical sign of a post-transfusion reaction. For three patients (one each anti-Jo(a), -AnWj, unidentified 'HTLA'), initial MMA was performed as part of an investigation of a suspected haemolytic reaction. In each case, the MMA accurately identified the unit responsible for the reaction.

CONCLUSION

Used as a crossmatch surrogate, the MMA provided valuable information in the decision of transfusing antigen positive blood to alloimmunised patients, avoiding delay because of the search of rare antigen negative units.

Assessment of the correlation of platelet morphology with in vivo recovery and survival

BACKGROUND

There is continuing interest in the development of in vitro tests evaluating the in vivo function, recovery, and survival of platelets stored for transfusion. A recent forum concluded that no completely reliable test exists, although discoid morphology indicates a platelet's good health. We evaluated a novel device, the NAPSAC (Noninvasive Assessment of Platelet Shape and Concentration), designed to determine noninvasively the proportion of discoid platelets in a stored concentrate, as well as platelet concentration.

STUDY DESIGN AND METHODS

Twenty-eight plateletapheresis concentrates stored 24 hours in PL-146 were evaluated. Percent discoid platelet results were correlated with radiolabeled autologous recovery and survival performed using 111Indium oxyquinoline and calculated using linear (L) and multiple-hit (M) models. pH of 8 concentrates was raised at the end of storage with 6N NaOH. Platelet concentration measured by NAPSAC and Coulter Thrombocounter C was compared in 256 plateletapheresis products.

RESULTS

Percent discoid platelets at 24 hours did not correlate significantly with platelet recovery or survival (recovery L = 0.29, M = 0.28; survival L = 0.16, M = 0.03). Raising the pH (mean 6.38 to 6.94) resulted in a significant increase in percent discoid platelets (21% to 41%). Platelet concentration values for both methods studied were linearly correlated with a slope of 1.01 +/- 0.03, r = 0.81.

CONCLUSION

Percent discoid platelets was not predictive of posttransfusion platelet recovery or survival. The results suggest that non-discoid platelets may survive posttransfusion and even revert to discoid shape, since raising the pH approximately doubled the percent of discoid platelets. The NAPSAC was shown to be a reliable instrument for noninvasively determining platelet concentration in PL-146 concentrates.

Hemolytic transfusion reaction due to anti-Tc(a)

BACKGROUND

Anti-Tc(a) detects a high-incidence antigen in the Cromer blood group system. Cromer system antibodies have not usually been associated with hemolytic transfusion reactions or hemolytic disease of the newborn.

CASE REPORT

Anti-Tc(a) (initially identified in the patient's serum in 1982) was not detected when she was admitted to the hospital with upper gastrointestinal. bleeding. Three units of red cells were administered. The patient was discharged, but was readmitted to the hospital after her hemoglobin fell to 7.1 g per dL. Antibody detection tests remained negative and three additional units were transfused. Over the next 7 days, her hemoglobin steadily fell to 5.5 g per dL. The level of lactate dehydrogenase rose to 1257, the plasma hemoglobin rose to >16 mg per dL, and the haptoglobin decreased to <6 mg per dL. Five days after transfusion, her direct antiglobulin test was weakly reactive with complement-specific antiglobulin reagents. Eluates were nonreactive. Anti-Tc(a) was detected in her serum; no other antibodies were detected. Differential typing failed to detect any circulating Tc(a+) red cells. The antibody was strongly reactive in a monocyte monolayer assay.

CONCLUSION

Although Cromer system antibodies have generally not been proven to be clinically significant in transfusion therapy, the destruction of red cells from six units of transfused Tc(a+) red cells in this patient indicates that anti-Tc(a) may have destructive potential in some patients.

Clinical application of functional assays for assessing the red cell antibody activity

Functional assays (the monocyte monolayer assay, the chemiluminescence test, and the antibody dependent cellular cytotoxicity assay) aim to reflect an interaction between sensitized red calls and Fc-gamma receptor bearing mononuclear cells, which plays the main role in immune destruction of erythrocytes in vivo. These assays have been used for predicting the clinical significance of antibodies in hemolytic disease of the newborn, in patients with alloantibodies requiring transfusion and patients suspected of autoimmune hemolytic anemia. This review presents a brief summary of the literature on this subject. In many cases (especially in hemolytic disease of the newborn, RhD) the results of bioassays can assess the functional activity of antibodies in vivo, but further investigation is needed to establish their real value for clinical practice.