Bowie, Ejw

Diagnosis of Bernard-Soulier syndrome (BSS) is complicated by the difficulty of separating the giant platelets from other blood cells to pursue analyses of platelet function and structure. We report on the utility of three whole blood assay techniques for diagnosis of a patient with BSS. To our knowledge, these three techniques have not been simultaneously applied or compared for efficacy in laboratory diagnosis of BSS. (1) Whole blood platelet aggregation responses, studied with an electrical impedence aggregometer, were equivalent to those more laboriously obtained using platelet-rich plasma prepared by unit gravity sedimentation, studied with an optical light transmittance aggregometer. Platelet aggregation responses were normal with ADP or collagen stimulation, and absent with Ristocetin or bovine plasma stimulation. (2) Whole blood radioimmunoassay of platelet glycoprotein (GP) expression was performed using iodinated murine monoclonal antibodies HP1-1D (anti-GP IIb/IIIa) and 6D1 (anti-GPlb, kindly supplied by Dr. Barry Coller, Stony Brook, NY). After incubation with citrated whole blood, centrifugation was used to separate cell-bound antibody which was quantitated with a gamma counter. The patient’s whole blood had a normal level of cell-bound GP Ilb/IIIa, but a markedly reduced level of cell-bound GP lb (5% of normal mean; n = 20). (3) Whole blood smear immunocytochemical staining with the monoclonals (indirect immuno-alkaline phosphatase technique), and qualitative analysis by light microscopy, revealed a marked reduction of GP lb expression by the patient’s giant platelets, whereas GP Ilb/IIIa expression was normal. This latter technique might be especially valuable as a screening technique when the patient is not directly available for laboratory study. Together with the patient’s life-long history of thrombocytopenia and moderate bleeding diathesis, and other laboratory observations including markedly prolonged bleeding times and reduced whole blood prothrombin consumption, these data established diagnosis of BSS. We conclude that these three relatively simple assays of platelets in whole blood should be of particular value in the laboratory differential diagnosis of patients with congenital thrombocytopenias and giant platelet syndromes.

Significant hemostatic abnormalities can occur during orthotopic liver transplantation (OLT). This study addressed three goals: 1)evaluation of the hemostatic mechanism at each stage of the OLT; 2) the relationship of the coagulation process with the thrombelastograph (TEG); and 3) comparison of results in patients requiring retransplantation or who died, with the overall pattern. To evaluate hemostasis during 50 consecutive OLTs, a detailed coagulation and TEG study was done. The surgical procedure was divided into the following stages: Stage I--induction of anesthesia to occlusion of blood flow to the patient’ s diseased liver; Stage II—occlusion of blood flow to the patient’ s diseased liver to reperfusion of the patient’ s new liver; and Stage III—reperfusion of the new liver until skin closure. 28 ml of arterial blood were sampled at the beginning and end of each stage and up to five days posttransplantation for the following: platelet count, prothrombin time, activated partial thromboplastin time, fibrinogen, prothrombin, factors V, VII, IX, and X, plasminogen, antiplasmin, antithrombin III (functional and immunologic), fibrinolytic split products, and TEG. The patient’ s core temperature and amount of blood products transfused were obtained intraoperatively during each of the six data times. The ischemia time of the donor liver was recorded. Significant hemostatic abnormalities developed during each of the 50 OLTs, especially during reperfusion of the donor liver. In some instances, this was corrected within one hour, but platelet counts continued to fall, and a number of coagulation factors rebounded only partially. The TEG values correlated with laboratory data and blood loss, but the correlations were not strong. The patient’ s requirement for red cells varied with the operative drop in temperature; however, the donor liver ischemia time and length of Stage II made no significant difference. It is concluded that 1) significant deterioration of coagulation factors occurs during OLT, 2) the TEG is an effective screening test that affords prompt information, 3) aggressive measures should be taken to maintain the patient’ s body temperature at 37°C, 4) patient outcome was not predicted by intraoperative hemostatic evaluation.

For further study of the porcine hemostatic mechanism, we have prepared murine monoclonal antibodies, and F(ab')2 and Fab fragments, specific for porcine platelet membrane glycoproteins GP lb and GP Ilb/IIIa. To avoid production of antibodies to von Willebrand factor (vWF), mice were immunized with platelets obtained from pigs with severe von Willebrand,s disease. One monoclonal antibody (PP3-4C), of IgG1 subclass, caused 85% inhibition of Ristocetin-induced platelet binding of 125I-vWF (porcine) at ≥12 µg IgG/ml. PP3-4C did not affect ADP or collagen-induced platelet aggregation nor inhibit 125I-fibrinogen (porcine) binding. Pepsin and papain digestion, respectively, were used to prepare PP3-4C F(ab')2 and Fab fragments. PP3-4C F(ab')2 at concentrations ≥12 µg/ml caused 80% inhibition of washed platelet agglutination in the presence of vWF and Ristocetin, whereas Fab fragments at concentrations ≥10 µg/ml caused 60% inhibition. Another monoclonal antibody (PP3-3A), of IgG1 subclass, completely inhibited ADP or collagen-induced platelet aggregation at an IgG concentration of 6 µg/ml. At 10 µg IgG/ml PP3-3A completely inhibited binding either of 125I-fibrinogen or of 125I-vWF to ADP-stimulated porcine platelets. PP3-3A did not affect vWF-dependent Ristocetin-induced platelet agglutination, nor 125I-vWF binding to platelets in the presence of Ristocetin. PP3-3A did not bind to platelets which were treated with 10 mM EDTA at 37°C for 60 min. F(ab')2 and Fab fragments were isolated from PP3-3A pepsin or papain digests. Both types of PP3-3A fragments caused 100% inhibition of ADP-induced platelet aggregation, at concentrations ≥6 yg/ml. Immunoprecipitation of surface-radiolabeled porcine platelets and subsequent SDS-PAGE demonstrated that PP3-4C recognized a glycoprotein with molecular weight of 140,000 (under reducing conditions), and 165,000 (non-reduced). PP3-3A recognized glycoproteins with molecular weights of 115,000 and 100,000 (reduced), and 130,000 and 80,000 (non-reduced). Neither monoclonal antibody bound to human platelets. These monoclonal antibodies to porcine platelet membrane glycoproteins which are analogues of human GP lb and GP Ilb/IIIa will be useful for in vitro and in vivo studies to further understanding of mammalian hemostatic mechanisms.

A 39-year-old 75 kg man with Type I Glanzmann's thrombasthenia developed recurring severe therapy-refractory nosebleeds, associated with nasal septal deformity, synechial scarring, and previous radiotherapy. During a 21 month period he required 16 hospitalizations for treatment of severe epistaxis. At initial hospitalization it was observed that his epistaxis ceased shortly after transfusion of 10 bags (units) of plasma cryoprecipitate (cryo), although transfusion with HLA-matched apheresis platelets from 3 donors, and topical therapy (cautery, packing), had been ineffective. Serum anti-platelet antibodies were not detectable by indirect immunofluorescence. During 9 subsequent hospitalizations his epistaxis stopped promptly (usually within 1 hour) following cryo transfusion (10 or 20 bags), including 6 occasions when cryo was the only therapy. On 6 additional occasions his epistaxis did not stop following cryo transfusion, but did stop after subsequent platelet transfusions or topical therapy. Eventually he underwent nasal septal reconstructive surgery surgery, and severe epistaxis has not recurred. Hemostatic studies, before and after cryo transfusions on 5 occasions, did not show improvement of platelet aggregation defects nor of Ivy bleeding times, although occasionally the volume of blood emanating from bleeding time punctures appeared decreased following cryo transfusion. Platelet glycoprotein (GP) IIb/IIIa antigen was measured in aliquots of 10 of the pools of cryo received by the patient (representing 100 bags of total volume 2200 ml), using an immunoradiometric assay (Nichols et al, Blood 68:300a, 1986). On average, the transfused cryo pools contained GP IIb/IIIa equivalent to 1.1 x 108 platelets/ml (range 0.6-1.7 x 108/ml. Our recently reported studies of blood bank cryo documented similar GP IIb/IIIa levels, and revealed that >93% of GP IIb/IIIa in cryo is present in the form of sedimentable membranous platelet macroparticles and microparticles. We hypothesize that the GPIIb/IIla-bearing platelet particles in transfused cryo might account for the improvement in hemostasis we frequently observed. We conclude that cryo transfusion deserves further study as a potentially useful therapeutic adjunct in promoting hemostasis in individuals with Glanzmann's thrombasthenia.

An automated method for specific factor assays has been developed using a novel thrombin-specific chromogenic substrate (developed by A. Aiyappa, Ph. D., Abbott Labs). For factors VIII, IX, XI and XII, the test system includes an ellagic acid activator and brain phospholipid in a calcium containing tris buffer pH 7.4. These are mixed with a plasma sample consisting of a mixture of specific factor deficient substrate and test plasma for 5 minutes and then the chromogenic substrate is added. After another 5 minutes the increase in optical density ΔOD is recorded. Normal plasma serially diluted in specific factor deficient substrate is used to construct a standard graph and test plasma results are interpolated from this.Fifty-four comparative assays have been done for factors VIII and IX and correlated with the results obtained from conventional clotting assays. For factor VIII the correlation coefficient (r)=0.935 (N=35) and for factor IX r=0.941 (N=19). While insufficient data exists to date for factors XI and XII, these assays appear to be comparable to the VIII and IX results.The assays for factors V, VII and X use a simplified system in that the chromogenic substrate and phospholipid are added together. The ΔOD is again recorded after 5 minutes. Test plasma results are interpolated from a standard graph constructed using serially diluted normal plasma as before. To date only the factor V assay has enough data to do a correlation with the clotting assays and r=0.953 (N=13) which is similar to the r value for the VIII and IX assays.Because of the widespread availability of the automated analyzer used in the assay and the standardization of end point determination it provides, specific factor assays might be made more widely available outside specialized coagulation centers.

BG 0 patients (pts) have lower risk for cardiovascular-thromboembolic disease than A-AB-B pts, particularly males. This might be related to blood hypocoagulability (lower Factor VIII). We report BG frequencies in our Caucasian renal transplant population divided in two groups, ES reflux nephropathy (RN) and ESRD of other etiologies excluding diabetes mellitus.BG 0 male pts are protected, especially for ESRN. To determine whether this sex dependency could be related to different VIII: RWF levels or PS, VIII:RWF levels (n=82) and 51Cr-labelled PS (n=74) were analyzed in controls according to sex and BG.VIII: RWF is sex independent and lower in BG 0. PS is BG independent and shortened in males. A hypercoagulable State reflected by high VIII: RWF and short PS might explain the increased risk of non-BG 0 males to develop ESRD. Non-BG 0 male pts with RN may be more susceptible to develop progressive RD.

Distinguishing between in vitro and in vivo release of platelet specific proteins has led to problems in interpretation of clinical studies with PF4, and with BTG.As part of a prospective study of peripheral occlusive arterial disease in diabetes mellitus PF4 and BTG were measured together by specific radioimmunoassay in four groups of subjects age 50-70 years. Groups included (1) 106 normal subjects (NC); (2) 126 with clinical and objective evidence (transcutaneous doppler ultrasound and treadmill exercise) of peripheral arterial occlusive disease (ASO); (3) 244 with diabetes mellitus without ASO and (4) 101 with both diabetes mellitus and ASO.PF4 did not distinguish among the four groups: NC vs ASO p=. 18, NC vs DM p=.52, NC vs DM+ASO p=.73, NC vs all diabetics p=.61, and NC vs all ASO p=.46. However, BTG did distinguish the groups with vascular disease from NC: NC vs ASO p=.02, NC vs DM+ASO p<.001, NC vs DM p=.32, DM vs DM+ASO p<.01, all ASO vs all nonASO p<.001.Normal range for PF4 is 0-13 ng/ml with a median of 3.0 ng/ml, a mean of 3.0 ng/ml, and SD 1.97. Normal range for BTG is 14-46 ng/ml with a median of 26 ng/ml, a mean of 27.2 ng/ml, and SD 10.3. When PF4 and BTG are correlated (all groups included) r=.41 p<.001.PF4 and BTG levels should be performed together. When done together low PF4 levels support the absence of in vitro platelet release due to sample collection and handling. BTG levels are significantly increased in subjects with peripheral arterial disease, supporting the active role of platelets in thrombotic occlusive arterial disease.

Murine monoclonal antibodies to porcine Willebrand factor were used to study the role of Willebrand factor in hemostatic plug formation in the in vivo and in vitro skin bleeding times. The in vivo assay requires the intravenous injection of antibody-containing mouse ascitic fluids into normal animals with subsequent ear bleeding time tests performed over a 24-hour period. The in vitro assay was carried out with heparinized normal porcine blood flowing through a 0.5 cm incision in an excised piece of porcine skin. The heat inactivated ascitic fluids, containing the antibodies, were used ;Ln these assays at final dilutions of 2 × 102 through 2 × 105 The 7 antibodies used comprised at least 5 groups with differing reactivities based on assays other than bleeding time tests. The antibody titers in a poreineg Willebrand factor-binding radioimmunoassay ranged from 108 through 1012 . Doses of 10HL of ascitic fluid/kg of body weight (approximately 2 × 103 final dilution) were able to transiently prolong the in vivo bleeding time without alteration of other VIII complex values (VIII:C, ristocetin cofactor activity and Vlll-related antigen). Higher doses resulted in bleeding times similar to von Willebrand pigs (>15 min) immediately following infusion, with a decay of the effect over the next 2 hours. At dilutions of 2 × 104 selected monoclonal antibodies interfered with hemostasis in the in vitro model whereas other antibodies inhibited only at 2 × 102 dilution. With one exception, the potencies of the antibodies appeared to be similar in both assays. The titer of the antibodies in the radioimmunoassay does not appear to correlate with prolongation of the in vitro bleeding time, suggesting specific reactivity with functional sites involved in hemostatic plug formatio.