Delayed hemolytic transfusion reaction (DHTR) is a life threatening complication of transfusion in sickle cell disease (SCD). This syndrome is underestimated because of a clinical picture that resembles a vaso-occlusive crisis (VOC) and the frequent absence of detectable antibodies. Several retrospective studies have evaluated the frequency of DHTR based on case reports. We conducted a prospective, longitudinal, single center study to determine the incidence of DHTR and the risk of developing DHTR depending on the transfusion regimen: chronic versus punctual.

Methods and patients

SCD patients aged over 18 years, undergoing a transfusion, were enrolled in this study. A total of 697 transfusion episodes (TE) in 312 patients were included during 30 months. Some patients had multiple TE during the period. The post transfusion outcome of the patients was assessed up to one month after the included TE. DHTR was confirmed based on the rapid disappearance of HbA (> 50% 15 days post-transfusion) associated with two of the following criteria up to three weeks after transfusion: VOC symptoms, dark urine, worsening anemia, increased LDH. Transfusion episodes were divided into chronic (336 TE in 111 patients) and punctual (361 TE in 201 patients). Chronic transfusions were defined as regular transfusions to treat chronic complications or for primary/secondary prevention of complications. Short transfusion program during pregnancy was considered as punctual transfusions if patients were not previously regularly transfused. The study obtained approval of the local Ethics Committee.


Follow-up of the patients after transfusion showed 15 DHTR during the study. They all developed in punctually transfused patients. Thus, patients who are transfused punctually have a significantly higher risk of developing DHTR than those in a regular transfusion program (p < 0.001). When considering only punctual transfusions, the incidence of DHTR is 4.2% per transfusion episode (IC 95% [2.6; 6.9]) and 7.5% per patient during the 30 months of the study (IC 95% [4.6; 12.4]). In these DHTR cases, the transfusion indication was surgery (n = 6), pregnancy (n = 3), acute chest syndrome (n = 3), stroke (n = 1), profound anemia (n = 1), and VOC prevention before a school exam (n = 1 case). Two patients died of multi-organ failure following severe intravascular hemolysis. The median hemoglobin decrease for all DHTR cases after the triggering transfusion was 4.4 g/dl [IQR 3.6-5.2]; the highest LDH level was 879 [IQR 680-1423]. Ten patients developed newly formed antibodies, but only five among them displayed antibodies with significant serological features (anti-Fya, anti-S, anti-Jka, anti-HI). In the five other cases, the antibodies were of unspecified specificity or auto antibodies in the RH blood group (the genetic RH background was known). Finally, antibodies were undetectable for five cases, confirmed by long-term patient follow up.


This prospective study demonstrates, for the first time, that DHTR is a frequent reaction in adult SCD patients, developing only in occasionally transfused patients. This finding highlights that adult patients with regular transfusion who did not previously encountered DHTR are not susceptible to developing this severe reaction. A mechanism linked to acute situations can be suggested as already shown for the induction of allo-immunization. However, many cases developed without detectable antibodies, confirming the complex pathophysiology of this syndrome. A bio-clinical scoring system to predict DHTR, based on this study, is under development and will be presented.


Michel:Roche: Research Funding.

Author notes


Asterisk with author names denotes non-ASH members.

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