ABSTRACT
Backgrour: Neonatal alloimmune thrombocytopenia (NAIT) is a result of fetomaternal incompatibility. Platelet destruction is caused by a maternal alntibody directed against a fetal platelet antigen inherited from the father and lacking on the mother's platelets. The incidence and features of transplacental alloimmunization depend on the frequency of expression of platelet specific antigens, which are highly variable among different populations. Aim: To determine the prevalence and characteristics of transplacental alloimmunization in a large, group of pregnant women in Chile. Material and methods: We, studied 3,041 samples obtained during the third trimester of gestation. In all samples, anti platelet antibodies were screened by ELISA with platelet membranes fixed to a microtiter plate. Positive samples were further studied for antigenic specificity with the monoclonal antibody specific immobilization of platelet antigens (MAIPA) test. Results: Anti platelet antibodies were found in 261 samples (8.5 percent). The MAIPA test identified 6 samples with antibodies directed against major platelet membrane glycoproteins, 2 anti GPIb, 2 anti GPIIb/IIIa and 2 anti GPIa/IIIa. In four cases, anti HLA antibodies coexisted. Two cases corresponded to well defined platelet antigen systems: one anti HPA-1a and one anti HPA-5b. No clinical evidence of thrombocytopenia of the newborn was detected in all these cases with anti GP antibodies. Conclusions: A prevalence of platelet specific antibodies of 0.2 por ciento with only one anti HPA-1a was detected. These findings are in contrast with those of other populations but in accordance with the low frequency of the HPA-1b/b phenotype in the Chilean population. The very low incidence of platelet specific antibodies and the lack of association with clinical thrombocytopenia in the newborn, do not support the recommendation of routine antenatal screening to all women in Chile
Subject(s)
Humans , Female , Pregnancy , Pregnancy Trimester, Third/blood , Immunity, Maternally-Acquired/physiology , Immune Tolerance/physiology , Enzyme-Linked Immunosorbent Assay , Blotting, Western , Antibody Specificity/immunology , Antigens, Human Platelet/isolation & purification , Pregnancy Complications, Hematologic/diagnosis , Prenatal Diagnosis/methods , Platelet Membrane Glycoproteins/analysis , Isoantigens/isolation & purificationABSTRACT
Background: Refractoriness continues to he a major complication of platelet transfusion therapy in patients with multiple transfusions: Despite most cases are secondary to non-immune causes, the most serious is that associated to alloimmunization. The incidence and consequences of HLA and non-HLA (platelet specific) antibodies are unknown in our country. Aim: To prospectively determinate the frequency and characteristic of post transfusion alloimmunization and the incidence of platelet specific antibodies. Patients and methods: Forty one adults and 24 children with a recently diagnosed malignancy and undergoing chemotherapy that required multiple transfusions were studied. Screening for antiplatelet antibodies (platelet membrane ELISA) was performed before the first transfusion, every four weeks or whenever the 1 hour corrected count increment for platelet transfusions was lower that 5000. Platelet specific antibodies werw identified with a monoclonal antibody-specific immobilization of platelet antigens (MAIPA), with anti-GPIIb, GPIIb/IIIa, GPIa/lia and anti-HLA class I. Results: Adult patients received an averafge of 10.2 ñ 5.5 units of red blood cells and 58.6 ñ 35.4 units of platelets. Children received 4.8 ñ 3.7 units of red blood cells and 9.6 ñ 6.7 units of platelets. HLA antibodies appeared in 7 of 41 adult patients (17 percent), platelet specific alloantibodies were found in two patients (one anti GP Ia/IIa and one anti GP ib). Platelet refractoriness appeared in three alloimmunized patients. No Child had detectable serum antibodies during follow up. Conclusions: Platel transfusion refractoriness of immune origin occurs infrequently in our population and the presence of platelet antibodies does not mean that it will appear. The use of leukocyte depleted blood components to prevent refractoriness cannot be justified at this time
Subject(s)
Humans , Male , Female , Infant , Child, Preschool , Adolescent , Adult , Middle Aged , Hematologic Neoplasms/immunology , Isoantibodies/isolation & purification , Platelet Transfusion/adverse effects , Anemia, Refractory/immunology , Antibody Formation/immunologyABSTRACT
Patients and methods: Five hundred eighty nine patients whose main symptom was the presence of mucocutaneous hemorrhages were studied. Bleeding time, platelet count, coagulant activity of factor VIII (FVIII:C), FvW: Ag and FvW:CoRis and ABO blood group were measured in all patients in a first stage. According to the results of these tests, further studies were decided. Results: In patients younger than 13 years old, males predominated and, in older patients, females consulted with higher frequency. There was a higher proportion of individuals with O blood type than in the normal population. Bleeding time was abnormal in 330 patients (56 percent). One hundred ten patients (19 percent) had von Willebrand disease and, among them, one third had a normal bleeding time. Isolated reduction of factor VIII activity was found in 66 patients (11 percent, 51 males) and 32 of these had normal bleeding time. Eighty one patients (14 percent) were considered to have an hereditary platelet function defect. A precise diagnosis was not achieved in 332 patients (56 percent). Conclusions: Among patients consulting for mucocutaneous hemorrhages, 19 percent had von Willebrand disease, 11 had an isolated reduction of factor VIII activity, 14 percent had platelet function defects and in 56 percent, a precise diagnosis was not reached
Subject(s)
Humans , Male , Female , Adolescent , Adult , Hemorrhagic Disorders/epidemiology , Mucous Membrane/physiopathology , von Willebrand Diseases/epidemiology , von Willebrand Factor/isolation & purificationABSTRACT
Hemophilia A is an X-linked disorder of coagulation caused by a deficiency of factor VIII. A large number of different mutations in the VIII gene have been identified. Thus, the detection of female carriers, depends upon the analysis of DNA polymorphism in and near the factor VIII gene. Our aim was to develop a strategy, earlier reported, for carrier testing in families at risk of hemophilia A. In this study, we analyzed the DNA polymorphisms in 26 affected families, with use of the factor VIII intragenic polymorphisms identified by the restriction enzymes Bcll and AlwNI and by differential hybridization with sequence-specific oligonuclaotide probes recognizing Bcll and AlwNI polymorphisms. While the DNA polymorphism detected by Bcll site in intron 18 of the factor VIII gene was informative for 30 percent families studied, the AlwNI/intron 7 polymorphism provided aditional information (4 percent). The carrier status of the remaining 58 percent could be determined utilizing the other polymorphisms suggested the strategy. The 2 polymorphic sites used combined with the other polymorphisms, intragenic and extragenic, can generate levels of informativeness greater than 98 percent. We concluded that the strategy for carrier testing would be a good alternative in genetic counselling for hemophilia A., but its limitations must be carefully taken into account
Subject(s)
Humans , Factor VIII/genetics , Introns/genetics , Hemophilia A/genetics , Blood Donors , Genetic Carrier Screening , Genetic Complementation Test/methodsABSTRACT
Activated protein C resistance (APCR) or factor V leiden has been recently described as the most prevalent hemostatic abnormality associated with venous thrombosis. In patients with familial thrombophilia, the prevalence of APCR is 19-60 percent and around 20 percent in sporadic venous thrombosis. APCR is usually measured by the degree of prolongation of activated Partial Thromboplastin Time (APTT) on patient's plasma, induced by addition of APC in comparison to normal plasma. At the molecular level the defect is caused by a single-point mutation in the gene for factor V (FV) (G1.691-A), that predict the replacement of Arg506 by Glutamine. This mutation makes activated factor V resistant to inactivation by APC. Since the prevalence of the defect is highly variable among different populations, the objective of this work was to study its frequency in our population and in patients with thrombophilia. We defined the normal range for APTT ratio (APTT+APC/APTT-APC) in a group of 73 healthy volunteers in whom the presence of FV Q506 mutation was searched using Mnll enzyme digestion of PCR amplified genomic fragment containing the nucleotide 1.691. The lower limit of APTT ratio stablished in this group was 2.13. APCR was found in 6 out of 159 control subjects (3.8 percent) and in 14/50 (28 percent) of patients with thrombosis. In 13 cases as a single defect and in 1 associated to type I protein C deficiency. All the APCR patients and control subjects were heterozygotes by gene analysis. The results demonstrate that in our population APCR is also the most common defect associated with thrombosis, in accordance with a high prevalence in the population. The ability to screen for this defect will permit the identification of carriers that would benefit preventive therapy at risk situations