Proficient and cost-effective approaches for the prevention and treatment of venous thrombosis and thromboembolism.

Thrombosis is clearly a common cause of death in the US. It is obviously of major importance to define the aetiology of deep vein thrombosis (DVT) as (i) many of these events are preventable if appropriate therapy, dependent upon the risk factors known is utilised; (ii) appropriate antithrombotic therapy will decrease risks of recurrence; (iii) the type of defect(s) and risk(s) will determine length of time the patient should remain on therapy for secondary prevention and (iv) if the defect is hereditary appropriate family members can be assessed. Aside from mortality, significant additional morbidity occurs from DVT including, but not limited to, stasis ulcers and other sequelae of post-phlebitic syndrome. Numerous studies have provided evidence that medical patients and patients undergoing surgery or trauma are at significant risk for developing DVT, including pulmonary embolism (PE). Thus, an important task for the clinician is to prevent DVT and its complications. It is important to define risk groups where prophylaxis must be considered. The attitudes and beliefs towards prophylaxis show great regional variations. This is true for the definition of risk groups, the proportion of patients receiving prophylaxis and prophylactic modalities used. For this reason, various 'consensus conference' groups have attempted to alleviate these problems; the primary mission of consensus guidelines is to provide optimal direction to the clinician in the setting of clinical practice. If the practice guidelines generated are successful they will assist clinicians in decision-making for their patients, and they will also provide protection against unjustified malpractice actions. Therapy may be complex, as clinical studies continue to identify more effective treatments. This review includes currently accepted approaches to the treatment of DVT. The clinical course of DVT is highly dynamic. When the response to therapy is not as expected, more than one cause of DVT may be present in a patient. Treatment must address the primary coagulopathy as well as any precipitating factors. The risk of pharmacological intervention must be balanced against potential benefit. If the incidence of DVT in a given disorder is low and if the mortality rate is similarly low, therapy with an agent known to be associated with a high risk for complications, such as warfarin, would not be indicated. If DVT is seen primarily after surgery or in other high-risk situations, therapy might be limited to a fixed time period. However, if the ongoing risk of DVT remains high or if a history of recurrent DVT dictates, lifelong therapy might be indicated. The recommendations presented are based upon published controlled trials; however, indications for therapy and therapeutic agents of choice will continually evolve. By applying the principles outlined in this review, substantial cost savings, reduction in morbidity and reductions in mortality should occur.

Antithrombin agents as anticoagulants and antithrombotics. Implications in drug development.

Synthetic and recombinant thrombin inhibitors have undergone several clinical evaluations for thrombotic and cardiovascular indications. While the initial trials were focused in coronary indications, more recently, these agents are also developed for the prophylaxis and therapeutic management of thromboembolic disorders. Hirudin, PEG-hirudin and argatroban are in advanced clinical development. Recombinant hirudin has been approved in Europe as a substitute anticoagulant for the management of HIT patients. Several additional clinical trials are currently carried out to demonstrate the usefulness of these agents in thrombotic and cardiovascular indications. Despite these developments such issues as dosage optimization, laboratory monitoring, neutralization and drug interactions require additional studies for the optimal development of these drugs.

Disseminated intravascular coagulation: objective clinical and laboratory diagnosis, treatment, and assessment of therapeutic response.

Current concepts of the etiology, pathophysiology, clinical and laboratory diagnosis and management of fulminant and low-grade disseminated intravascular coagulation (DIC) have been presented. Considerable attention has been devoted to interrelationships within the hemostasis system. Only by clearly understanding the pathophysiological interrelationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. Objective clinical and laboratory criteria for diagnosis of DIC have been delineated, thus avoiding needless confusion and empirical decisions regarding the diagnosis. Many therapeutic decisions to be made are controversial and will remain so until more is published about specific therapeutic modalities and survival patterns. Also, therapy must be highly individualized depending on the nature of DIC, age, etiology of DIC, site and severity of hemorrhage or thrombosis, and hemodynamic and other clinical parameters. Also presented are clear criteria for severity of DIC and objective criteria for defining a response to therapy. Also, since it is often difficult for the individual physician to decide when to stop expensive therapy, objective criteria by which therapy may be stopped when continuation is likely fruitless are presented as a guideline.

Blood protein defects associated with thrombosis. Laboratory assessment.

This review has stressed the common hereditary and acquired blood protein defects associated with thrombosis. The most common of the hereditary defects appear to be antithrombin, protein C, and protein S deficiency, and the most common acquired defects are anticardiolipin antibodies and the lupus anticoagulant. Therefore, these are the defects which should first be searched for in an individual with unexplained thrombosis. If these more common defects are not found, the rarer defects, including HC-II, plasminogen, or TPA deficiency, dysfibrinogenemia, elevated PAI-1, or heterozygous homocystinemia should be looked for. The incidence of activated protein C co-factor deficiency (APC resistance) is not yet clear but may also represent a common defect. PAI-1 defects may, with time, be shown to be common. Finding these defects has important implications for therapy for the individual patient and for the institution of family studies to identify, inform, and possibly treat others at risk. It is expected that as knowledge of hemostasis expands, more hereditary and acquired defects, such as elevated lipoprotein(a) or defects of extrinsic (tissue factor) pathway inhibitor (EPI, TFPI), may be associated with enhanced risks for thrombosis.

Fully automated antithrombin-III assays by synthetic substrate on the Multistat III.

Antithrombin-III assays are performed to assess response to heparin therapy and efficacy of antithrombin concentrate therapy and in diagnosing hereditary thrombophilia, deep venous thrombosis, pulmonary embolus, and disseminated intravascular coagulation. Synthetic substrate assays for antithrombin-III are the methods of choice; however, most existing assay systems are semiautomated. A fully automated, antithrombin-III assay using the Kabi Chromogenic Synthetic Substrate S-2238 COATEST on the MULTISTAT III has been developed. This assay was compared with the Dade Protopath fluorometric assay. The correlation (r-sq) between the two assay systems was 0.82. Additionally, a three-way assay comparison was also performed, incorporating a new fluorometric substrate for antithrombin-III. The three-way comparative assays revealed correlation as follows: MULTISTAT III fluorometric assay and the MULTISTAT III/Kabi COATEST assay r-sq = 0.90; MULTISTAT III fluorometric assay and the Dade fluorometric assay r-sq = 0.86; and the MULTISTAT III/Kabi COATEST assay and the Dade Protopath fluorometric assay r-sq = 0.95. These automated assays were extremely cost effective and were a fraction of the cost of performing other types of antithrombin-III assays.