Showing papers in "Seminars in Thrombosis and Hemostasis in 1984"

Protein S and the regulation of activated protein C.

Abstract: The studies that have been carried out to date suggest that protein S can function as a cofactor protein in the activated protein C catalyzed inactivation of Factor Va. This conclusion is supported by the observation that protein S and activated protein C can form a lipid bound complex that can inactivate Factor Va more rapidly than does soluble activated protein C. Protein S has a number of properties in common with other cofactor proteins. It has been isolated as a distinct entity from plasma, it has no known intrinsic activities, and its effect is maximal when it is bound to a lipid surface. Protein S appears to be important in the regulation of the plasma anticoagulant activity of activated protein C as well. This is supported by the lack of anticoagulant activity of activated protein C in protein S-depleted plasma and by the observation that protein S is important in the species specificity of the anticoagulant activity of the enzyme. Future work in this area is needed to ascertain if there are any clinical manifestations of protein S deficiencies that correlate with the cofactor activity that has been established.

Clinical Studies of Protein C

Abstract: The major clinical importance of plasma protein C is attested to by the strong association between inherited protein C deficiencies of half normal levels and recurrent venous thromboembolic disease. Homozygous protein C deficient individuals do not survive beyond infancy without continuous therapeutic intervention. The spectrum of protein C deficiency is becoming broader and includes patients with both abnormal molecules and half normal levels of functionally active molecules. Rarely, a few young adults with thrombosis have been identified with protein C levels below 25%. Studies of protein C activity have been hampered until the very recent developments of functional assays of plasma protein C. Application of these assays to a wide variety of clinical situations involving thrombotic complications is just beginning and may lead to an explosive proliferation of new data that should prove most fascinating and give much further insight into the contributions of protein C in the regulation of thrombosis.

Development and performance characteristics of a competitive enzyme immunoassay for fibrinopeptide A.

Abstract: A simple nonisotopic method for the quantitation of FPA in biologic samples has been developed utilizing a competitive enzyme immunoassay technique. The performance characteristics of these assays have been investigated in both the experimental and clinical settings and were found to be satisfactory for the routine clinical application. This method is comparable to a commercially available RIA kit (Mallinckrodt, St. Louis, MO) in both the clinical and normal samples. This assay can be used in the diagnosis of hypercoagulable states associated with various diseases. Subclinical activation of coagulation can be readily assessed when the global tests, such as the prothrombin time, partial thromboplastin time, and thrombin time, have no value. This test is of value in the monitoring of the newer antithrombotic agents, such as the low molecular weight heparin fractions that do not effect the global assays, such as the partial thromboplastin time. Similarly, the risk of thrombosis associated with the use of procoagulant therapy, such as the activated prothrombin complex concentrates, can be readily assessed using this assay. It is proposed that the FPA measurement may also provide useful information on the quality control of various plasma-based therapeutic products, such as plasma concentrates or activated prothrombin complex concentrates. FPA generation tests are currently proposed for the screening of antithrombotic and prohemostatic agents.

Platelet-released proteins as molecular markers for the activation process.

Abstract: The desire to have a specific, sensitive marker for platelet activation was originally thought to lie in the development of RIAs for BTG and PF4. Although this wish has not been denied, the interpretation of the information obtained from such an analysis has proved far less rewarding. The principal challenge of these procedures is based upon the lack of a cause and effect relationship between a given disease and platelet activation, coupled with the differential clearance rate and mechanism for each of the discussed proteins. Thus, we have seen that the renal clearance rate and mechanism for each of the discussed proteins. Thus, we have seen that the renal clearance of a patient should be noted prior to interpreting the elevation of BTG. Similarly, since PF4 is removed from the circulation so rapidly, its plasma values tend to be lower than BTG by a factor of 5, although the significance of the BTG to PF4 ratio is questioned. Administration of heparin results in a heparin-induced increase in plasma PF4 levels but not for BTG, and this PF4 increase can be as great as 20-fold. PF4 and BTG values are also directly increased by pressure increases. Taken individually, these mediators each compromise the ability to correlate the significance of platelet protein increases with any single pathologic condition. When viewed collectively, an analysis of platelet-released proteins is best interpreted as an indication that the functional integrity of the platelet has been perturbed; the direct relationship of disease processes to platelet release is far from certain and is simply documented by the use of such described procedures. The final note of caution for these assays is to be found in the recent summary analysis of the standardization of both BTG and PF4. In this study, considerably greater variation among laboratories was noted for PF4 than was seen for BTG, and the study directors concluded that comparisons of results between laboratories should be regarded as unreliable due mainly to the use of different standards for each protein in a given laboratory. The final note of caution for these assays is to be found in the recent summary analysis of the standardization of both BTG and PF4. In this study, considerably greater variation among laboratories was noted for PF4 than was seen for BTG, and the study directors concluded that comparisons of results between laboratories should be regarded as unreliable due mainly to the use of different standards for each protein in a given laboratory.

Molecular markers of contrast media-induced adverse reactions.

Abstract: Currently used routine laboratory screening methods are not reliable in the prediction of contrast media-related adverse reactions. Cost-effective laboratory methods for various molecular markers of pathophysiologic activation have now become available. In vitro activation tests in high-risk patients may prove to be useful in the prediction of contrast-induced activation of various adverse reactions. If prior clinical evaluation of a patient suggests an ongoing pathologic process, profiling of the following molecular markers may prove to be useful and helpful in avoiding contrast-induced adverse reactions: Fibrinopeptide A, platelet factor 4, thromboxane B2, 5-HETE, physiologic inhibitors of proteases, B beta 15-42 related peptides, bradykinin/kininogen, and anaphylactozins. In patients suspected of reacting to contrast agents, a small dose of 1 to 5 ml can be injected as a bolus and molecular marker profiling on blood drawn after the infusion may prove to be useful screening tests. Additional clinical studies are needed to prove this. However, this screening test should be performed with extreme caution, since some of the patients are known to react to as little as 1 ml dose. The safety of newly developed nonionic contrast agents can be readily assessed by profiling various molecular markers of adverse reactions, which provide a more reliable and quantitative assessment of contrast-induced adverse reactions. Based on molecular marker profiling, various prophylactic agents can be given to high-risk patients to avoid contrast-induced adverse reactions.

Diagnostic efficacy of a simple radioimmunoassay test for fibrinogen/fibrin fragments containing the B beta 15-42 sequence.

Abstract: A simple RIA method for B beta 15-42 RPs has been evaluated in our laboratory to investigate experimental and clinical fibrinolytic states. The assay utilizes bentonite precipitation to remove cross-reacting fibrinogen. Due to the heterogeneity in molecular weights of the B beta RPs, the results are expressed as nanograms per milliliter. The linear range of the assay is 2 to 40 ng/ml, with a capability of detecting up to 200 ng/ml. A special anticoagulant mixture (heparin or EDTA/aprotinin) is required for sample collection. Certain precautions in the care and handling of specimens are also necessary. Increased levels of B beta RPs were observed in the following conditions: malignancy (associated with increased release of tissue plasminogen activators), pancreatitis, liver diseases, pregnancy, and postexercise testing (associated with increased release of tissue plasminogen activators). Increased levels of B beta RPs were also found during thrombolytic therapy, anabolic steroid treatment, prothrombin complex concentrate therapy, blood component therapy, and low molecular weight heparin subcutaneous therapy (associated with an increase in tissue plasminogen activator release). Our studies suggest that B beta RPs are sensitive molecular markers of the endogenous activation of fibrinolytic system and may provide useful diagnostic information on a pathologic process that often remains undetectable by routine laboratory methods.

Performance characteristics of a simple radioimmunoassay for fibrinopeptide A.

Abstract: FPA, although identified 15 years ago, is now becoming an increasingly important diagnostic tool in the evaluation of the hemostatic process. Since this peptide is generated in very small amounts, only very sensitive methods, such as RIA, are useful for its quantitation. Measurement of this peptide allows for a most precise and reliable monitor of any ongoing thrombotic event in which thrombin is generated. Commercial kits have become available for fast and simple clinical evaluations of FPA. The Mallinckrodt RIA Quanti FPA kit has proved its reliability in precision, accuracy, fast turnaround time, and applicability to a routine laboratory setting. This assay kit was evaluated in our laboratory in various aspects. The following points summarize our finding: FPA is a useful diagnostic parameter to evaluate the activation of coagulation pathways in various pathologic states. A study of 170 normal plasma samples resulted in 1.7 +/- 0.5 ng/ml. No significant difference between males and females was noted. FPA levels are evaluated in patients with hypercoagulable states, DIC, and related thrombotic states. Our studies have shown that FPA levels are also elevated in certain cancers, postsurgical states, and certain other conditions in which the coagulation process is activated. During therapeutic heparinization, FPA levels are reduced; thus this form of therapy can be monitored using FPA levels. High-risk population (thrombotic) can be easily screened using FPA measurement. We propose that a multicenter study on FPA levels be conducted to prove its clinical relevance to other diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Pigmented purpuric eruptions.

Abstract: The pigmented purpuric eruptions most likely represent a group of clinical patterns of erythrocyte extravasation due to pericapillary inflammation. This inflammatory reaction may be in response to an immunologic reaction of some type, as suggested by immunopathologic studies and by the drug-induced pigmented purpuras. It is important to recognize this group of cutaneous purpura primarily to distinguish the pigmented purpuric eruptions from other types of purpura which are associated with systemic illness. The various eponyms or descriptive types of the pigmented purpuric eruptions are of historical and dermatologic interest; there is little clinical use in distinguishing among the types for a given patient.

Clinical implications of molecular markers in hemostasis and thrombosis.

Abstract: The general availability to all clinical laboratories of assays of molecular markers of the hemostasis system now offers the clinician the opportunity to screen selected high-risk patients and potentially to offer therapy that will ward off a significant and often catastrophic event. In addition, these molecular markers permit a rapid differential diagnosis of many disorders that are often confusing and often difficult, if not impossible, to differentiate using the more traditional global screening tests of hemostasis. This short review has served only to point out the importance of these newly developed molecular markers of the hemostatic system and only selected disorders have been highlighted with respect to the ability of these molecular markers to aid in a prethrombohemorrhagic event and to aid in a specific differential diagnosis in certain selected thrombohemorrhagic disorders. It is anticipated that more experience with these molecular markers with more patient populations will most likely greatly expand their usefulness in a wide variety of thrombohemorrhagic disorders, thus leading to enhanced medical care for patients.