Risk factors for alloimmunization by patients with sickle cell disease.

Blood transfusion in patients with sickle cell disease (SCD) is limited by the development of alloantibodies to erythrocytes. In the present study, the frequency and risk factors for alloimmunization were determined. Transfusion records and medical charts of 828 SCD patients who had been transfused and followed at the Belo Horizonte Blood Center, Belo Horizonte, MG, Brazil, were retrospectively reviewed. Alloimmunization frequency was 9.9% (95% CI: 7.9 to 11.9%) and 125 alloantibodies were detected, 79% of which belonged to the Rhesus and Kell systems. Female patients developed alloimmunization more frequently (P = 0.03). The median age of the alloimmunized group was 23.3 years, compared to 14.6 years for the non-alloimmunized group (P < 0.0001). Multivariate analyses were applied to the data for 608 hemoglobin (Hb) SS or SC patients whose number of transfusions was recorded accurately. Number of transfusions (P = 0.00006), older age (P = 0.056) and Hb SC (P = 0.02) showed independent statistical associations with alloimmunization. Hb SC patients older than 14 years faced a 2.8-fold higher (95% CI: 1.3 to 6.0) risk of alloimmunization than Hb SS patients. Female Hb SC patients had the highest risk of developing alloantibodies. In patients younger than 14 years, only the number of transfusions was significant. We conclude that an increased risk of alloimmunization was associated with older patients with Hb SC, specially females, even after adjustments were made for the number of transfusions received, the most significant variable.

Risk factors for alloimmunization by patients with sickle cell disease

Blood transfusion in patients with sickle cell disease (SCD) is limited by the development of alloantibodies to erythrocytes. In the present study, the frequency and risk factors for alloimmunization were determined. Transfusion records and medical charts of 828 SCD patients who had been transfused and followed at the Belo Horizonte Blood Center, Belo Horizonte, MG, Brazil, were retrospectively reviewed. Alloimmunization frequency was 9.9 percent (95 percent CI: 7.9 to 11.9 percent) and 125 alloantibodies were detected, 79 percent of which belonged to the Rhesus and Kell systems. Female patients developed alloimmunization more frequently (P = 0.03). The median age of the alloimmunized group was 23.3 years, compared to 14.6 years for the non-alloimmunized group (P < 0.0001). Multivariate analyses were applied to the data for 608 hemoglobin (Hb) SS or SC patients whose number of transfusions was recorded accurately. Number of transfusions (P = 0.00006), older age (P = 0.056) and Hb SC (P = 0.02) showed independent statistical associations with alloimmunization. Hb SC patients older than 14 years faced a 2.8-fold higher (95 percent CI: 1.3 to 6.0) risk of alloimmunization than Hb SS patients. Female Hb SC patients had the highest risk of developing alloantibodies. In patients younger than 14 years, only the number of transfusions was significant. We conclude that an increased risk of alloimmunization was associated with older patients with Hb SC, specially females, even after adjustments were made for the number of transfusions received, the most significant variable.

Estudo das causas da isoimunização materna por antígenos eritrocitáros entre gestantes acompanhadas no Serviço de Medicina Fetal do HC-UFMG / Study of the causes of maternal erithrocytic antigen isoimmunization among pregnant women followed at the Fetal Medicine Service - HC-UFMG

Objetivo: Analisar as causas da isoimunização materna por antígenos entrocitários entre as gestantes acompanhadas no Serviço de Medicina Fetal do HC-UFMG, no período de junho de 1996 a junho /2003. Pacientes e Método: Trata-se de estudo prospectivo, qual 256 gestantes sensibilizadas por antígenos eritrocitários foram acompanhadas no Centro de Medicina Fetal do HC-UFMG. As pacientes foram avaliadas quanto ao passado obstétrico, visando identificar as causas de isoimunização. Resultados: Entre os 256 casos acompanhados, em 185(72,3%) a causa de isoimunização foi a ausência de profilaxia pós-parto; a transfusão sangüínea incompatível foi a responsável por 34 casos (13,3%) e a falta de profilaxia pós-aborto, por 29 casos (11,3%). Os oito casos restantes (3,1%) ocorreram durante o período gestacional. Conclusão: As principais causas de isoimunização materno-fetal continuam se relacionando à etiologia obstétrica, principalmente à falta de imunoprofilaxia no pás-parto e no pós-aborto. Portanto, a isoimunização, em nosso meio, pode ser facilmente prevenível com o uso da imunoglobulina anti-Rh (D), conforme rotina já estabelecida há décadas.

Objective: To analyze the causes of maternal erithrocytic antigen isoimmunization among pregnant women followed at the Fetal Medicine Service Hospital das Clínicas - Universidade Federal de Minas Gerais (FMSHC), from June/1996 to June/2003. Methods and Material: A prospective study, consisting of 256 pregnant women with sensitization by erithrocytic antigen were followed at the FMSHC. These patients were evaluated regarding the obstetric history, in order to identify the causes of isoimmunization. Results: In 185 cases (72.3%), isoimmunization was caused by lack of postpartum prophilaxy. Incompatibility in blood transfusion and absence of post-abortion prophilaxy were responsible for 34 (13.3%) and 29 cases (11.3%), respectively. The remaining eight cases (3.1%) occurred during gestational period. Conclusion: The main cause of fetal-maternal isoimmunization is still related to obstetric etiology, mainly to absence of postpartum or post-abortion immunoprophilaxy. Therefore, isoimmunization, in our population, can be easily prevented by the use of anti-Rh (D) immune globulin according to established routines.

Anemia fetal detectada por dopplervelocimetria da artéria cerebral média / Fetal anemia detected by doppler velocimetry of middle cerebral artery

A Anemia é condição clínica que pode acometer o feto gravemente, por diversas razões, sendo a isoimunização do sistema Rh a mais freqüente. O padrão-ouro para o diagnóstico intra-útero é a cordocentese e análise da hemoglobina fetal. As consequências para o feto podem ser hidropisia fetal, insuficiência cardíaca, óbito intra-útero ou neonatal, parto prematuro, dentre outras. Quando há redução na concentração da hemoglobina fetal, a viscosidade sanguínea é diminuída e a velocidade aumentada. Alguns vasos fetais foram estudados, como artéria umbilical, aorta e carótida interna. Para avaliação da velocidade do pico sistólico é necessário ângulo inferior a 20graus, por isso, determinou-se como ideal a artéria cerebral média. O desempenho do pico sistólico por dopplervelocimetria da artéia cerebral média na predição da anemia fetal está sendo exaustivamente estudado. Os autores fazem revisão sobre como a dopplervelocimetria de artéria cerebral média pode auxiliar no manejo da anemia fetal

Isoinmunización RH: manejo actual / Isoinmunización RH: present handling

La incompatibilidad rh materno fetal es un factor que complica aproximadamente 1 de cada 1000 embarazos en los EE.UU, constituye la principal causa de muerte fetal o neonatal por enfermedad hemolítica. Nuevas técnicas como la cordocentesis, transfusión intrautterina han mejorado el pronóstico en estas pacientes. En la presente revisión comentaremos los avances acerca del manejo de la isoinmunización Rh.

[Partial deletion of the D antigen in a family group. Determination of its antigenic density by flow cytometry]. / Delección parcial del antígeno D en un grupo familiar. Determinación de su densidad antigénica por citometría de flujo.

UNLABELLED: Mutations within the genetic Rh system can produce partial deletions of one or more epitope of the D antigen, known as incomplete D. These people, classified Rh positive, are capable of producing anti-D antibodies when exposed to D positive red blood cells (rbcs). We describe the study of a Rh positive, 34 year old, spanish-indian ("mestiza") female patient, in whose blood anti-D antibodies were detected after a blood transfusions. The results of the tests showed a partial deletion of the D antigen in the patient and three of her family members. PATIENTS AND METHODS: The following tests were done to the patient and her family members: 1) ABO and Rh typing; 2) Direct antiglobulin test; 3) Detection of irregular antibodies in their blood serum; 4) Rh genotype; 5) Cross matching of the patient's serum with rbcs of her Rh positive relatives; 6) Titration of a monoclonal anti-D (IgM) and a polyclonal anti-D (IgG) of human origin with the patient's rbcs and with Rh positive rbcs of her family members whose erythrocytes didn't react with the patient's serum; 7) Measurement of the antigenic density of the D antigen by flow cytometry (indirect immunofluorescence) in the rbcs of the patient and in those family members who had the defect, using a polyclonal anti-D (IgG). RESULTS: 1) An anti-D antibody which didn't react with its own Rh positive rbcs was found in the patient's serum; 2) This antibody didn't react with the Rh positive rbcs of her father and two out of her 4 brothers; 3) The cytometric study of these cells (R)r) showed a immunofluorescence pattern weaker than the control cells of the same genotype, but with a variable expression between 15 to 41%. CONCLUSIONS: The study showed: 1) The presence of an anti-D antibody in a Rh positive patient who had been previously sensitized (by blood transfusion); 2) This antibody was able to react with Rh positive rbcs but not with those of the patient and her family members who had the same partial deletion; 3) The defect was transmitted heterozygously, with a high degree of penetration, but with variable expression; 4) A low antigenic density for her D antigen by flow cytometry.