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High circulating levels of the procoagulant molecule tissue factor (TF) are associated with thrombosis in a variety of diseases including unstable angina, cancer, and sepsis. Currently, there are no clinical assays to measure the level of TF activity in whole blood. We present an assay called Tissue Factor Clotting Time ("TiFaCT") that detects fibrin formation in human blood. The mean baseline clotting time in a healthy population was 472 +/- 94 s (mean +/- SD, n = 150). Bacterial lipopolysaccharide (LPS or endotoxin) shortened the clotting time in a time-dependent manner. Inhibitory anti-TF antibodies prolonged the clotting time of LPS-stimulated blood, indicating that the shortened clotting time was due to induction of TF expression. Patients with unstable angina had shortened mean baseline clotting time (284 +/- 86, n = 13) compared with healthy volunteers (474 +/- 98, n = 30), suggesting that these patients had elevated levels of circulating TF. The TiFaCT assay should prove clinically useful in quantifying the levels of circulating TF in patients at risk of thrombosis.

To determine the medical and laboratory characteristics of bacteremia secondary to transfusion of microbiologically contaminated platelet concentrates.Febrile transfusion reactions were prospectively monitored over 42 months. Units involved in reactions were evaluated with Gram's stain and culture tests.Comprehensive cancer center.Patients receiving platelet transfusions for thrombocytopenia secondary to bone marrow failure.Seven cases of transfusion-associated sepsis were observed. Multidonor platelet products stored for 5 days resulted in an incidence of sepsis five times higher than those stored for 4 days or less (P less than .01). Investigation indicates that contamination most likely occurred at the time of blood collection. Clinically, septic reactions were associated with greater temperature elevations (average increase, 2.0 degrees C) than febrile reactions to sterile products.Contamination of platelet concentrates remains a significant clinical problem. Septic episodes may be reduced by transfusion of platelets with shorter storage intervals.

Baka is a platelet alloantigen whose putative allele, Bakb, has not been identified previously. By using a serum, “Har,” obtained from a patient with posttransfusion purpura, we describe the platelet alloantigen Bakb. The Har serum reacted with an NP-40-extractable platelet membrane protein of 142 kd with mobility similar to platelet glycoprotein IIb alpha. We found that the antigen recognized by the Har serum is inherited in an autosomal dominant mode with an apparent gene frequency of .39. Chi-square analysis of observed and expected phenotype frequencies indicated that serum Har recognizes Bakb, the anticipated allele of Baka. Our findings provide new evidence for polymorphism of glycoprotein IIb and for the association of posttransfusion purpura with alloimmunization to determinants on this glycoprotein.

We report a patient who, while receiving probenecid and colchicine for acute gouty arthritis, developed severe hemolytic anemia in association with a generalized rash. The hemolysis was immune mediated as shown by a positive direct Coombs' test. In vitro hematologic studies showed that a probenecid dependent antibody was present.

The effect of repeated phlebotomy on serum immunoreactive erythropoietin levels was studied prospectively in 69 autologous blood donors. At the time of the initial phlebotomy, 11 men (33%) and two women (6%) were anemic; during the course of blood donations, anemia (defined as a hematocrit less than 0.41 for men and less than 0.36 for women) developed in an additional 17 men (71%) and 14 women (45%). Although there was an increase in the level of serum immunoreactive erythropoietin with successive phlebotomies, the increase was not substantially out of the normal range. The lack of an erythropoietic response to repeated phlebotomies in association with the small increment in the serum erythropoietin level was not due to iron deficiency, since the level of red-cell free protoporphyrin did not increase in these patients. We conclude that within the hematocrit range permissible for autologous blood donation, the degree of anemia experienced is insufficient to initiate an adequate increase in erythropoietin production; as a consequence, mild anemia develops in a majority of donors, and the volume of blood donated is inadequate to meet their operative needs.