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J G McFarland

Publications and source records attributed to J G McFarland.

At least 19 recordsLinked to original sources
PubMed2005

Prospective evaluation of a new platelet glycoprotein (GP)-specific assay (PakAuto) in the diagnosis of autoimmune thrombocytopenia (AITP).

Assays measuring platelet-associated immunoglobulin G (PAIgG), while highly sensitive, lack specificity in diagnosing autoimmune thrombocytopenia (AITP). We prospectively evaluated a new commercially available glycoprotein (GP)-specific assay, the PakAuto (GTI, Brookfield, WI), for its clinical usefulness in distinguishing immune from nonimmune thrombocytopenia (TP), in 216 patients with autoimmune TP (both primary "idiopathic" and "secondary") and 46 patients with TP due to other causes. This assay is designed to detect both platelet-associated (direct assay) and plasma (indirect assay) antiplatelet antibodies specific for GPs IIb/IIIa, Ib/IX, and Ia/IIa. The mean platelet counts of the immune (79 +/- 7 x 10(9)/L) and nonimmune groups (78 +/- 7 x 10(9)/L), were similar (P=0.95). The direct assay was positive in 114/216 patients with AITP (53%), and 13/46 with nonimmune TP (28%). Among the AITP group, the majority (61%) of patients with positive test results had autoantibodies reactive against all three GP targets. The sensitivity, specificity, positive, and negative predictive values for the direct PakAuto were 53%, 72%, 90%, and 24%, respectively, comparable to previously published experience of GP-specific assays. However, in some cases of TP due to nonimmune cause, the PakAuto was highly specific. Only 3 of 22 patients with gestational and 1 of 8 with familial/congenital TP had a positive direct assay, indicating that the test may be particularly useful for excluding an immune etiology for TP in certain patient subgroups.

Adolescent↗
PubMed2003

TRALI due to granulocyte-agglutinating human neutrophil antigen-3a (5b) alloantibodies in donor plasma: a report of 2 fatalities.

BACKGROUND: TRALI is usually an immunologic reaction to WBC antibodies in infused plasma and ranks second only to ABO mismatch as a cause of transfusion-associated death. Implicated donors are usually multiparous women (>/=3 pregnancies). STUDY DESIGN AND METHODS: Two fatal cases of TRALI were evaluated by reviewing clinical and laboratory findings and characterizing alloantibodies present in donor plasma. Investigation for WBC antibodies was by lymphocytotoxicity (LCT), FlowPRA (FlowPRA, One Lambda, Inc.) and granulocyte immunofluorescence and agglutination assays. Patient 1 was a 62-year-old man with chronic T-cell lymphocytic leukemia, and Patient 2 was a 54-year-old woman undergoing a cadaveric kidney transplant. Both patients developed acute respiratory distress and hypotension during (Patient 1) and approximately 30 minutes after (Patient 2) transfusion. Fulminant pulmonary edema ensued in both cases necessitating mechanical ventilation and both patients died within 24 hours of the onset of respiratory complications. RESULTS: The donors of the implicated blood components were women with a history of two pregnancies but no blood transfusions. Weak apparently panreactive granulocyte antibodies were detected with flow cytometry. However, in the granulocyte agglutination test, strong antibodies specific for human neutrophil antigen (HNA)-3a (5b) were identified in both donors. CONCLUSION: It is concluded that female blood donors with only two previous pregnancies can form clinically important granulocyte-reactive alloantibodies leading to fatal TRALI reactions in recipients. The sometimes devastating consequences of TRALI should prompt the development of strategies to prevent or reduce its incidence. Further research is warranted to investigate recipient and donor factors responsible for TRALI, including whether 5b (HNA-3a) alloantibodies are especially prone to cause severe reactions, and to better characterize the HNA-3a (5b) antigen, particularly at the molecular level.

Agglutination↗
PubMed2003

Severe neonatal alloimmune thrombocytopenia caused by antibodies to human platelet antigen 3a (Baka) detectable only in whole platelet assays.

BACKGROUND: Maternal antibodies that cause neonatal alloimmune thrombocytopenia are commonly identified by solid-phase assays that detect the causative antibodies on the basis of their reactions with specific PLT glycoproteins. Two cases of severe neonatal alloimmune thrombocytopenia caused by maternal antibodies specific for human PLT antigen 3a (HPA-3a [Baka]) that failed to give the expected reactions in some solid-phase assays were recently encountered. STUDY DESIGN AND METHODS: PLT-reactive antibodies were characterized by three different solid-phase assays and by flow cytometry. RESULTS: The two maternal antibodies gave negative reactions in the antigen capture ELISA, modified antigen capture ELISA, and MoAb immobilization of PLT antigens tests but reacted strongly in flow cytometry with intact PLTs that were HPA-3a+. Other sera samples specific for HPA-3a reacted equally well in all assays. CONCLUSIONS: The two antibodies appear to recognize an epitope on the HPA-3a+ form of glycoprotein IIb that is lost when PLTs are solubilized in detergent, as required for solid-phase assays. The diagnosis was made in these cases because no HLA antibodies were present, allowing an HPA-3a-specific reaction to be identified with intact PLTs as targets. Such antibodies are likely to be overlooked when HLA antibodies are also present.

Adult↗
PubMed2001

Heparin is not required for detection of antibodies associated with heparin-induced thrombocytopenia/thrombosis.

Heparin-induced thrombocytopenia (HIT), with or without thrombosis, is a common and often serious complication of heparin therapy. Platelet-activating, heparin-induced antibodies characteristic of HIT are thought to be specific for complexes formed between platelet factor 4 (PF4) and heparin, and such complexes are routinely used for antibody detection. We studied the binding of HIT antibodies to PF4 complexed with heparin fractions of uniform molecular size or linear polyanions other than heparin and found that many compounds other than heparin form complexes with PF4 that are suitable for antibody detection, provided they carry strong negative charges spaced about 0.5 nm apart along the molecular backbone and are of sufficient length to span about 40% of the circumference of the PF4 tetramer. Polyvinyl phosphonate was among the compounds that were equivalent to heparin. Thus neither a polysaccharide chain nor sulfate side groups--the hallmarks of heparin structure--are required for HIT antibody detection. The findings support the view that antibodies associated with HIT are specific for conformational changes that take place in the positively charged PF4 molecule when it reacts with a suitable, linear polyanion.

Antibody Specificity↗
PubMed2001

Initial fetal platelet counts predict the response to intravenous gammaglobulin therapy in fetuses that are affected by PLA1 incompatibility.

OBJECTIVE: Fetal alloimmune thrombocytopenia is the result of maternal fetal platelet antigen incompatibility; intracranial hemorrhage is its most serious complication. Our previous studies have demonstrated an inability to accurately predict fetal platelet counts in this disorder. The goal of the present investigation was to identify factors that would predict the response of the fetal platelet count to therapy so that use of fetal blood sampling could be minimized. STUDY DESIGN: Patients who were eligible for the study were all those who (1) had alloimmune thrombocytopenia secondary to Pl(A1) (HPA-1a, Zw(A)) platelet antigen incompatibility, (2) were treated with maternally administered intravenous immunoglobulin at 1 g/kg of body weight per week, with or without low dose steroids, and (3) had percutaneous fetal blood sampling before the initiation of therapy (first fetal blood sampling) and again 3 to 7 weeks afterwards (second fetal blood sampling). RESULTS: In this retrospective review, 74 patients who were affected by alloimmune thrombocytopenia had a median platelet count of 21,000 per microliter at the first fetal blood sampling and 47,000 per microliter at the second fetal blood sampling, with a median increase in platelet count of 24,000 per microliter. Response to treatment was defined as either (1) an improvement in platelet count (the second fetal blood sampling greater than the first fetal blood sampling, and second fetal blood sampling > 20,000 per microliter) or (2) a minimal decline in platelet count (the first fetal blood sampling > or = 40,000 per microliter and the difference between the first and second fetal blood sampling < or = 10,000 per microliter). The first fetal blood sampling had prognostic value for the second fetal blood sampling (P = .0001), although the previous sibling birth platelet count and history of sibling intracranial hemorrhage did not predict the platelet count at the first or second fetal blood sampling or the change in platelet count between the samplings. When the patients were segregated to first fetal blood sampling of > 20,000 per microliter versus < or = 20,000 per microliter, the response rates for the 2 groups were 89% (33/37 patients) versus 51% (19/37 patients; P = .001). CONCLUSION: In fetal alloimmune thrombocytopenia secondary to Pl(A1) platelet antigen incompatibility, fetuses with platelet counts > 20,000 per microliter at the initiation of therapy were predicted to maintain their platelet count at the second fetal blood sampling at > 20,000 per microliter. The characteristics of the previous sibling, as previously reported, did not predict the initial fetal blood sampling, the second fetal blood sampling, or the response to treatment.

Adult↗
PubMed2001

Anti-HPA-3A induces severe neonatal alloimmune thrombocytopenia.

OBJECTIVE: Fetal and neonatal alloimmune thrombocytopenia (AIT) caused by feto-maternal incompatibility at the HPA-1a (PLA-1) locus is well characterized. Alloimmunization and disease caused by HPA-3a is rare. STUDY DESIGN: We conducted a retrospective analysis of all known cases of AIT caused by HPA-3a incompatibility identified at 3 major reference laboratories from 1986 to 1996. Platelet antigen typing and antibody specificity were determined by serologic evaluation. In some cases confirmatory genotyping was performed. RESULTS: Fourteen cases of anti-HPA-3a-induced AIT in 11 families were identified. Five patients had a previous affected sibling, and 2 cases were firstborn children. All patients had severe thrombocytopenia at birth (platelet count <20 x 10(9)/L). Regardless of therapy, the median time to platelet recovery was 6 days (range, 3 to 23 days). Two (15%) patients had documented intracranial hemorrhage, 1 with severe sequelae including apnea and convulsions. A literature review describing 16 additional patients corroborates the finding of severe thrombocytopenia and a significant incidence of intracranial hemorrhage caused by HPA-3a incompatibility. CONCLUSION: AIT caused by incompatibility of HPA-3a is similar in severity to disease caused by incompatibility of HPA-1a. Affected families should be appropriately counseled and considered for antenatal therapy.

Antigens, Human Platelet↗
PubMed1999

Minimal evidence of platelet and endothelial cell reactive antibodies in thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is a syndrome characterized by microvascular thrombosis with thrombocytopenia and end-organ injury. Evidence suggests that platelet or endothelial cell injury may be initial pathological events in TTP. A number of factors in patient plasma, including immunoglobulins, have been proposed to mediate cellular injury in TTP. However, systematic analyses of TTP patient plasma for the presence of platelet or endothelial cell antibodies are lacking. We, therefore, analyzed 48 TTP patient plasma samples for the presence of platelet and endothelial cell antibodies by using enzyme-linked immunosorbent assay, flow cytometry, and microlymphocytotoxicity. Twelve of 48 TTP patient samples (25%) reacted against purified platelet glycoproteins. Nine (19%) also contained antibodies that bound to allogeneic target platelets in flow-cytometric assays. Nine of 48 samples (19%) contained antibodies to human umbilical vein endothelial cells in flow-cytometric assays, and seven of 48 patient samples (15%) bound to human dermal microvascular endothelial cells. Six of 48 (13%) patient plasma samples contained antibodies that bound to human umbilical vein endothelial cells activated with gamma-interferon and tumor necrosis factor-alpha. Of twenty samples that were reactive in one or more platelet or endothelial cell assay, eight contained human leukocyte antigen antibodies reactive in microlymphocytotoxicity. These studies demonstrate that antibodies reactive against platelet or endothelial cell antigens are not prevalent in TTP, and that more than a third of antibodies detected are human leukocyte antigen alloantibodies. Our findings suggest that autoantibodies against platelets or endothelial cells are not important in the pathogenesis of this syndrome.

Autoantibodies↗
PubMed1999

Perioperative blood transfusions: indications and options.

A reevaluation of the indications for and alternatives to transfusion of allogeneic blood was precipitated by transfusion-induced HIV. The transfusion trigger has shifted from an optimal hemoglobin level and hematocrit (10/30) to that level of hemoglobin necessary to meet the patient's tissue oxygen demands. This critical level can best be determined by physiologic measurements. A number of autologous blood options can reduce the patient's allogeneic blood needs. Pharmacologic measures to increase hemoglobin levels (erythropoietin) and to decrease blood loss at surgery are discussed as are the potential contributions of blood substitutes to transfusion support of the surgical patient.

Blood Substitutes↗
PubMed1998

Platelet and neutrophil alloantigen genotyping in clinical practice.

Immune responses to platelet and neutrophil alloantigens are involved in the pathogenesis of several clinical syndromes including: neonatal alloimmune thrombocytopenia (NATP), post-transfusion purpura (PTP), refractory responses to platelet transfusion, neonatal alloimmune neutropenia (NAN), transfusion-related acute lung injury (TRALI), and chronic benign autoimmune neutropenia of infancy. Initially, platelet alloantigens were only characterized serologically. Subsequently, they were localized to specific platelet surface glycoprotein structures and ultimately defined to the level of nucleic acid polymorphisms on platelet glycoprotein genes. These advances allowed the tools of molecular biology to be applied to typing for platelet alloantigens. The advantages of such typing methods include: 1) patient platelets are no longer required for the typing assays, and therefore, platelet types can be established on extremely thrombocytopenic samples (by using peripheral blood white blood cells [WBC]); 2) The genotyping methods eliminate the requirement for rare serologic reagents. A number of different genotyping methods have been developed. These include: restriction fragment length polymorphism (RFLP), sequence specific primers (SSP), and Dot-Blot hybridization. Clinical applications of this methodology include: determining the platelet genotype of fetuses at risk for NATP, in the diagnosis of PTP, and identifying causes of refractory responses to platelet transfusions. Analogous to platelet alloantigens, a limited number of neutrophil alloantigens can now be determined by molecular biologic methods. The new methods obviate the need to isolate fresh neutrophils for serologic typing and do not require rare serologic reagents. To date, molecular polymorphisms associated with alloantigens on the neutrophil Fc gamma RIIIb surface glycoprotein have been elucidated. These include the allo-antigens NA1, NA2, and SH.

Antigens, Human Platelet↗
PubMed1997

Fetal alloimmune thrombocytopenia.

BACKGROUND: Alloimmune thrombocytopenia is a serious fetal disorder resulting from platelet-antigen incompatibility between the mother and fetus. The diagnosis is usually made after the discovery of unexpected neonatal thrombocytopenia. Approximately 10 to 20 percent of affected fetuses have intracranial hemorrhages, one quarter to one half of which occur in utero. We studied the correlates of thrombocytopenia in affected fetuses. METHODS: We studied 107 fetuses with alloimmune thrombocytopenia at a mean (+/-SD) gestational age of 25+/-4 weeks, before their entry into one of three treatment protocols. The fetuses were initially evaluated because an older sibling had been given this diagnosis at birth. We compared the initial platelet counts in utero in these 107 fetuses with the platelet count at birth and the history of intracranial hemorrhage in the affected sibling. RESULTS: The initial platelet count was < or =20,000 per cubic millimeter in 53 of the 107 fetuses (50 percent), including 21 of 46 fetuses (46 percent) studied before 24 weeks of gestation. The 97 fetuses with PI(A1) incompatibility had more severe thrombocytopenia than the 10 fetuses with other antigen incompatibilities. Among seven fetuses with platelet counts of more than 80,000 per cubic millimeter that were not treated initially, the counts decreased by more than 10,000 per cubic millimeter per week. Although 41 fetuses had initial platelet counts that were lower than those measured at birth in an older affected sibling, only a history of antenatal intracranial hemorrhage in the sibling predicted greater severity of thrombocytopenia in the fetus. Only one treated fetus had an intracranial hemorrhage, and the thrombocytopenia resolved after birth in all cases. CONCLUSIONS: Fetal alloimmune thrombocytopenia occurs early in gestation, is severe, and is more severe in fetuses with an older affected sibling who had had an antenatal intracranial hemorrhage.

Fetal Blood↗
PubMed1997

Thrombotic thrombocytopenic purpura: early and late responders.

Thrombotic thrombocytopenic purpura (TTP) is characterized by micro-angiopathic hemolytic anemia (MAHA), thrombocytopenia, neurological symptoms, renal involvement, and fever. We describe our experience in 70 serially encountered TTP patients in the last decade who were treated with a standard therapeutic plasma exchange (TPE) protocol. Seventy percent of the patients were females. The median age of the patients was 43 years (range: 8-80). Sixty patients (85.7%) had a complete response to TPE therapy. This represented 91% of 66 who received at least one TPE. Ten patients died, two patients died before and two during the first plasma exchange. The median number of TPEs performed was nine (range: 1-85). Thirty-five (58%) out of 60 responded to 3-9 TPEs, and 25 (42%) required 10-34 TPEs for the response. The median total plasma volume exchanged was 28 liters (range: 2.7-250 L) and the mean plasma volumes exchanged during each procedure was 3.2 (SD +/- 1.09 L). The patients were classified into early responders (ER) and late responders (LR). ERs had a mean platelet count of 180 x 10(9)/L by Day 5, mean LDH of 643 IU/L by Day 7, and required median of seven TPEs. LRs had a mean platelet count of 122 x 10(9)/L by Day 5, mean LDH of 885 IU/L by Day 7, and required median of 19 TPEs (P = 0.001). The platelet counts were significantly higher (P = 0.01-0.03) in ERs on Days 1, 3, and 5 as compared to LRs but the LDH did not differ significantly. Seventy-seven percent of LRs had exacerbation of TTP and 18% had relapse as compared to 7% each in ERs. Thirteen patients were in coma/semicoma at presentation. Out of these, six died, making coma a bad prognostic indicator. Five of the seven survivors in coma had received two single-plasma volume exchanges on Day 1. In conclusion, 91% of TTP patients had an excellent response to plasma exchange therapy with FFR Coma/ semicoma appears to be a bad prognostic indicator. LRs needed prolonged treatment with a greater number of patients experiencing exacerbation and relapse of TTP as compared to ERs.

Adolescent↗
PubMed1996

A dinucleotide deletion in exon 4 of the PlA2 allelic form of glycoprotein IIIa: implications for the correlation of serologic versus genotypic analysis of human platelet alloantigens.

Platelets from a patient with a suspected case of posttransfusion purpura were subjected to alloantigen phenotyping and found to express the PlA1, but not the PlA2, allelic form of human platelet membrane glycoprotein (GP) IIIa on the platelet surface. However, genotyping showed unambiguously that the patient carried the genes for both of these GPIIa alleles. Based on these results, we postulated that the PlA2 allele was silent, ie, that this patient was a carrier for Glanzmann thrombasthenia (GT). Quantitative analysis of GPIIb-IIIa surface expression showed only 20,000 GPIIb-IIIa receptors/platelet, approximately half of the value obtained with control platelets. Southern blot analysis showed no large deletions or insertions within the GPIIIa gene, and amplification of all 14 exons encoding GPIIIa resulted in the production of normal sized polymerase chain reaction (PCR) products in all cases. DNA-sequence analysis showed an AG dinucleotide deletion affecting codons 210 and 211 within exon 4 of the GPIIIa gene, leading to a change in reading frame and the creation of a stop codon 38 nucleotides down-stream. The predicted truncated protein consists of only the first 223 of the normal 762 amino acids, thus accounting for the failure to express the PlA2 allele on the platelet surface. While encountered only rarely, carriers of either GT or Bernard Soulier syndrome that are at the same time heterozygous for human platelet alloantigenic epitopes found on GPIb, GPIIb, or GPIIIa have the possibility to give discrepant results when comparing genotypic versus phenotypic analysis. In such situations, the combination of serologic and DNA-based evaluation contributes complementary and beneficial diagnostic information than either one alone are able to provide.

Alleles↗
PubMed1996

Antiplatelet antibody testing in thrombocytopenic pregnant women.

OBJECTIVE: The purpose of the study was to attempt to distinguish pregnant women with gestational thrombocytopenia from those with idiopathic immune thrombocytopenia by eight different platelet antibody assays. STUDY DESIGN: Sera from pregnant women with presumed gestational thrombocytopenia (n = 160) and idiopathic immune thrombocytopenia (n=90) were prospectively tested for indirect and platelet-associated immunoglobulins G and M and complement C3, as well as for serotonin release. After the results were analyzed, a subset of patients were subsequently analyzed for circulating antiplatelet antibody directed against platelet membrane glycoprotein GPIIb/IIIa. RESULTS: Indirect immunoglobulin G was significantly greater in the 85 women with idiopathic immune thrombocytopenia than in the 129 women with gestational thrombocytopenia (p<0.001). Platelet-associated immunoglobulin G was elevated in the majority of women, both those with gestational thrombocytopenia and those with idiopathic immune thrombocytopenia. There were also no statistically significant difference in the values for platelet-associated C3 or indirect immunoglobulin M and C3. Levels of platelet-associated immunoglobulin M showed a tendency to be higher in women with gestational thrombocytopenia (p=0.04), as did the values in the serotonin release assay (p=0.06). CONCLUSION: Our data demonstrate that patients with gestational thrombocytopenia had surprisingly high levels of platelet-associated immunoglobulin despite mild thrombocytopenia. Comparison of a relatively large number of patients with idiopathic immune thrombocytopenia and gestational thrombocytopenia indicates that women with idiopathic immune thrombocytopenia cannot be distinguished from those with gestational thrombocytopenia by means of one or more of the prototypic platelet antiglobulin tests currently in use. Our preliminary data with glycoprotein-specific assays indicate that they may be more useful.

Autoantibodies↗
PubMed1996

Antenatal management of alloimmune thrombocytopenia with intravenous gamma-globulin: a randomized trial of the addition of low-dose steroid to intravenous gamma-globulin.

OBJECTIVES: Our purposes were to investigate maternal infusions of intravenous gamma-globulin, to prevent intracranial hemorrhage, and to determine whether 1.5 mg dexamethasone and 60 mg prednisone per day add to the effect of intravenous gamma-globulin. STUDY DESIGN: Fifty-four women with alloimmune thrombocytopenia and thrombocytopenic fetuses were randomized to intravenous gamma-globulin 1 gm/kg per week with or without dexamethasone. Nonresponders after 4 to 6 weeks received continued intravenous gamma-globulin plus 60 mg of prednisone per day ("salvage"). RESULTS: Dexamethasone did not add to the effect of intravenous gamma-globulin. Overall, there was a mean platelet increase from the first to the second fetal blood sampling of 36,000/microliters (n = 47) and from the first fetal blood sampling to birth of 69,000/microliters (n = 54). A total of 62% to 85% of fetuses responded. There were no intracranial hemorrhages. "Salvage" increased the platelet count in 5 of 10 nonresponders to intravenous gamma-globulin. CONCLUSION: Intravenous gamma-globulin treatment is appropriate for thrombocytopenic fetuses with alloimmune thrombocytopenia before use of weekly in utero platelet transfusions, even in severe thrombocytopenia.

Cerebral Hemorrhage↗
PubMed1996

Genotyping of KEL1 and KEL2 of the human Kell blood group system by the polymerase chain reaction with sequence-specific primers.

BACKGROUND: Kell is a major antigenic system in human red cells, with more than 20 identified antigens. KEL1 and KEL2 are two opposing low- and high-frequency alleles. Immunization to KEL1 is clinically significant, because anti-KEL1 can cause severe reactions to transfusion of incompatible blood, as well as hemolytic disease of the newborn. At the nucleotide level, the difference between the KEL2 and KEL1 alleles is a single-base change within exon 6 that results in the substitution of methionine (ATG) for threonine (ACG) at position 193. STUDY DESIGN AND METHODS: An assay using polymerase chain reaction and sequence-specific primers to genotype for the KEL1 and KEL2 alleles has been developed. It uses two allele-specific forward primers for either KEL1 or KEL2 and a single reverse-consensus primer. RESULTS: A validation study of 42 serologically typed samples (5 KEL:1,-2 [K+k-]; 23 KEL:1,2 [K+k+]; and 14 KEL:-1,2 [K-k+]) was performed. A concordance rate of 100 percent (42/42 samples) was observed between polymerase chain reaction with sequence-specific primers and serologic typing. CONCLUSION: This rapid, nonradioactive, Kell system genotyping assay does not require the additional steps of probe hybridization or restriction enzyme digestion. This application of polymerase chain reaction with sequence-specific primers should prove particularly useful in Kell system genotyping of amniotic cells to identify pregnancies at risk for hemolytic disease of the newborn.

Alleles↗