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Shannon M Bates

Publications and source records attributed to Shannon M Bates.

18 recordsLinked to original sources
PubMed2006

An evaluation of D-dimer in the diagnosis of pulmonary embolism: a randomized trial.

BACKGROUND: It may be safe to omit additional diagnostic testing in selected patients with suspected pulmonary embolism (PE) who have a negative D-dimer test, but this approach has never been evaluated in a randomized, controlled trial. OBJECTIVE: To determine if additional diagnostic testing can be safely withheld in patients with suspected PE who have negative erythrocyte agglutination D-dimer test results. DESIGN: Randomized comparisons in 2 subgroups of a prospective multicenter study. SETTING: 7 university hospitals. PATIENTS: 1126 outpatients or inpatients with suspected PE; of these, 456 patients with negative erythrocyte agglutination D-dimer test results were randomly assigned to the intervention groups. Patients were classified into 2 clinical probability groups: those with a low clinical probability of PE (low-probability group) and those with a moderate or high clinical probability of PE, a nondiagnostic ventilation-perfusion lung scan, and no evidence of proximal deep venous thrombosis on bilateral ultrasonography (moderate- or high-probability group). INTERVENTIONS: The experimental intervention for both probability groups was no further diagnostic testing for PE. The control intervention for the low-probability group was a ventilation-perfusion lung scan followed by ultrasonography of the proximal deep veins of the legs on the same day. If the lung scan was nondiagnostic, ultrasonography of the legs was repeated 7 and 14 days later. The control intervention for the moderate- or high-probability group was ultrasonography of the proximal deep veins of the legs after 7 and 14 days. In the control and experimental groups, anticoagulation was withheld or withdrawn if PE was not diagnosed. MEASUREMENTS: Symptomatic venous thromboembolism (VTE) during 6 months of follow-up. RESULTS: Prevalence of VTE was 15.2% in the 1126 enrolled patients. In the low-probability group, VTE occurred during follow-up in 0 of 182 patients who had no additional diagnostic testing and in 1 of 185 patients who had additional testing (difference, -0.5 percentage point [95% CI, -3.0 to 1.6 percentage points]). In the moderate- or high-probability group, VTE occurred during follow-up in 1 of 41 patients who had no additional diagnostic testing and in 0 of 41 patients who had additional testing (difference, 2.4 percentage points [CI, -6.4 to 12.6 percentage points]). LIMITATIONS: The authors could not enroll 2000 patients as originally planned; 3 randomly assigned patients did not receive the allocated intervention, and 7 received inadequate follow-up. Personnel who performed follow-up evaluations were not blinded to the results of diagnostic testing at enrollment or to allocation group assignments. CONCLUSION: In patients with a low probability of PE who have negative D-dimer results, additional diagnostic testing can be withheld without increasing the frequency of VTE during follow-up. Low clinical probability and negative D-dimer results occur in 50% of outpatients and in 20% of inpatients with suspected PE.

Fibrin Fibrinogen Degradation Products↗
PubMed2006

The status of new anticoagulants.

Currently available anticoagulants include heparin, low-molecular weight heparin, fondaparinux and warfarin. Despite advances with low-molecular weight heparin and fondaparinux, the currently available agents have limitations that have provided the impetus for the development of new drugs for prevention and treatment of both venous and arterial thromboembolism. Novel anticoagulants targeting specific steps in coagulation are in various stages of development. This paper reviews the pharmacology of these new agents and describes the results of clinical trials with new anticoagulants in more advanced stages of clinical testing.

Anticoagulants↗
PubMed2005

Are brand-name and generic warfarin interchangeable? A survey of Ontario patients and physicians.

BACKGROUND: The issue of therapeutic equivalence has been a source of controversy in Canada since the approval of generic warfarin products in 2000. OBJECTIVES: We surveyed Ontario patients and physicians on perceptions of generic warfarin and brand substitution. METHODS: Self-administered questionnaires employed 7.0-point Likert scales of agreement. Patient participants were drawn from a thromboembolism clinic in Hamilton, Ontario. Physician participants were from a random sample of 375 Ontario family physicians, internists, cardiologists and hematologists. RESULTS: Eighty-one patients responded: 52% female, mean age 63.4 years and 63% brand-name warfarin users. Overall, 33% of respondents agreed or strongly agreed that they would feel comfortable taking generic warfarin. However, seventeen percent agreed or strongly agreed that generic warfarin was neither as safe nor as effective as brand-name warfarin, with this view more common amongst patients taking brand-name than those taking generic warfarin. One hundred and ten (29.3%) physicians returned the survey--29% females, mean age 45.3 years, 22% family physicians. Forty-four percent agreed or strongly agreed that they would rather prescribe brand-name than generic warfarin for patients starting warfarin therapy, while 40.7% agreed or strongly agreed that they would not feel comfortable switching from brand-name to generic warfarin. However, only 19.4% of physicians who had switched patients from brand-name to generic warfarin actually reported difficulties in managing the switch. CONCLUSION: While most patients and physicians appear to have accepted the principle of therapeutic equivalence of generic and brand-name warfarin, a sizable minority has concerns that could influence prescribing and compliance.

Anticoagulants↗
PubMed2005

Are brand-name and generic warfarin interchangeable? Multiple n-of-1 randomized, crossover trials.

BACKGROUND: Warfarin is a commonly used anticoagulant in North America. Several generic formulations have been approved, raising concern over the safety and efficacy of these products compared with brand-name Coumadin. OBJECTIVE: To ensure that generic warfarin products can be safely interchanged with Coumadin. METHODS: Multiple n-of-1 randomized, double-blind, crossover trials switched outpatients (N = 7) between a generic warfarin formulation (Apo-warfarin) and Coumadin over 30 weeks. Study patients took each drug for five 3-week periods, with international normalized ratio (INR) measurements taken twice per period. Inter- and intrapatient differences between generic warfarin and Coumadin were compared, and overall study patient results were compared with those of a Coumadin control group. RESULTS: There were no differences between warfarin products in terms of mean INR results or number of dosage adjustments required. There also was no difference in INR variation based on warfarin formulation (p > 0.69), nor was a patient and warfarin interaction found (p > 0.81). The INR results were not influenced by whether patients were maintained on Coumadin only (control group) or interchanged between Coumadin and generic warfarin (p = 0.98). CONCLUSIONS: It appears that patients can safely and effectively switch between generic warfarin and Coumadin.

Aged↗
PubMed2005

A randomized trial of diagnostic strategies after normal proximal vein ultrasonography for suspected deep venous thrombosis: D-dimer testing compared with repeated ultrasonography.

BACKGROUND: With suspected deep venous thrombosis and normal results on proximal vein ultrasonography, a negative d-dimer result may exclude thrombosis and a positive D-dimer result may be an indication for venography. OBJECTIVE: To evaluate and compare the safety of 2 diagnostic strategies for deep venous thrombosis. DESIGN: Randomized, multicenter trial. SETTING: Four university hospitals. PATIENTS: 810 outpatients with suspected deep venous thrombosis and negative results on proximal vein ultrasonography. INTERVENTIONS: Erythrocyte agglutination D-dimer testing followed by no further testing if the result was negative and venography if the result was positive (experimental) or ultrasonography repeated after 1 week in all patients (control). MEASUREMENTS: Symptomatic deep venous thrombosis diagnosed initially and symptomatic venous thromboembolism during 6 months of follow-up. RESULTS: Nineteen of 408 patients (4.7%) in the D-dimer group and 3 of 402 patients (0.7%) in the repeated ultrasonography group initially received a diagnosis of deep venous thrombosis (P < 0.001). During follow-up of patients without a diagnosis of deep venous thrombosis on initial testing, 8 patients (2.1% [95% CI, 0.9% to 4.0%]) in the D-dimer group and 5 patients (1.3% [CI, 0.4% to 2.9%]) in the repeated ultrasonography group developed symptomatic venous thromboembolism (difference, 0.8 percentage point [CI, -1.1 to 2.9 percentage points]; P > 0.2). Venous thromboembolism occurred in 1.0% (CI, 0.2% to 2.8%) of those with a negative D-dimer result. LIMITATIONS: Seventy patients (8.6%) deviated from the diagnostic protocols, and 9 patients (1.1%) had inadequate follow-up. CONCLUSION: In outpatients with suspected deep venous thrombosis who initially had normal results on ultrasonography of the proximal veins, a strategy based on D-dimer testing followed by no further testing if the result was negative and venography if the result was positive had acceptable safety and did not differ from the safety of a strategy based on withholding anticoagulant therapy and routinely repeating ultrasonography after 1 week.

Female↗
PubMed2005

New anticoagulants: beyond heparin, low-molecular-weight heparin and warfarin.

The limitations of traditional anticoagulants, heparin and warfarin, have prompted the development of new anticoagulant drugs for prevention and treatment of both venous and arterial thromboembolism. After a brief review of thrombogenesis and its regulation, this paper focuses on new anticoagulant agents in more advanced stages of clinical testing.

Animals↗
PubMed2005

"ProC Global": a functional screening test that predicts recurrent venous thromboembolism.

Abnormalities of the Protein C (PC) pathway are found in the majority of patients with thrombophilia. ProC Global is a coagulation assay that reflects the net effect of the PC pathway by measuring the activated partial thromboplastin time (APTT) of patient and control plasma, before and after activation of endogenous PC by Protac, a snake venom. Previous studies have suggested that abnormalities in this test are associated with an increased risk of venous thromboembolism (VTE). A retrospective analysis was performed using frozen plasma samples from 140 patients with confirmed VTE to determine whether an abnormal ProC Global result (in the presence and in the absence of known abnormalities in the PC pathway) is a predictor of initial and recurrent VTE. Patients were tested for the presence of activated protein C resistance, Factor V Leiden, PC and protein S (PS) deficiency, and non-specific inhibitor positivity. Mean ProC Global results were significantly lower in patients with recurrent VTE than in patients without recurrent VTE. The association between abnormal ProC Global result and recurrent VTE showed a strong trend, before (odds ratio, OR 3.6) and after (OR 3.1) exclusion of known thrombophilic abnormalities. Patients with a first episode of idiopathic VTE also expressed significant lower ProC Global results than those with secondary VTE. After exclusion of known PC pathway abnormalities, there was a statistically significant association between abnormal ProC Global and initial idiopathic VTE (p=0.04). These results suggest that ProC Global may serve as a predictor of recurrent VTE and potentially for first episode of idiopathic VTE. ProC Global may help identify patients at increased risk of initial and recurrent VTE.

Activated Protein C Resistance↗
PubMed2004

Use of antithrombotic agents during pregnancy: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.

This chapter about the use of antithrombotic agents during pregnancy is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: for women requiring long-term vitamin K antagonist therapy who are attempting pregnancy, we suggest performing frequent pregnancy tests and substituting unfractionated heparin (UFH) or low molecular weight heparin (LMWH) for warfarin when pregnancy is achieved (Grade 2C). In women with acute venous thromboembolism (VTE), we recommend adjusted-dose LMWH throughout pregnancy or IV UFH for at least 5 days, followed by adjusted-dose UFH or LMWH for the remainder of the pregnancy and at least 6 weeks postpartum (Grade 1C+). In patients with a single episode of VTE associated with a transient risk factor that is no longer present, we recommend antepartum clinical surveillance and postpartum anticoagulants (Grade 1C). In patients with a single episode of VTE and thrombophilia or strong family history of thrombosis and not receiving long-term anticoagulants, we suggest antepartum prophylactic or intermediate-dose LMWH or minidose or moderate-dose UFH, plus postpartum anticoagulants (Grade 2C). In patients with multiple (two or more) episodes of VTE and/or women receiving long-term anticoagulants, we suggest antepartum adjusted-dose UFH or adjusted-dose LMWH followed by long-term anticoagulants postpartum (Grade 2C). For pregnant patients with antiphospholipid antibodies (APLAs) and a history of two or more early pregnancy losses or one or more late pregnancy losses, preeclampsia, intrauterine growth retardation, or abruption, we suggest antepartum aspirin plus minidose or moderate-dose UFH or prophylactic LMWH (Grade 2B). We suggest one of the following approaches for women with APLAs without prior VTE or pregnancy loss: surveillance, minidose heparin, prophylactic LMWH, and/or low-dose aspirin, 75 to 325 mg/d (all Grade 2C). In women with prosthetic heart valves, we recommend adjusted-dose bid LMWH throughout pregnancy (Grade 1C), aggressive adjusted-dose UFH throughout pregnancy (Grade 1C), or UFH or LMWH until the thirteenth week and then change to warfarin until the middle of the third trimester before restarting UFH or LMWH (Grade 1C). In high-risk women with prosthetic heart valves, we suggest the addition of low-dose aspirin, 75 to 162 mg/d (Grade 2C).

Contraindications↗
PubMed2003

Emerging anticoagulant drugs.

The limitations of traditional anticoagulants, heparin and warfarin, have prompted the development of new anticoagulant drugs for prevention and treatment of both venous and arterial thromboembolism. After a brief review of thrombogenesis and its regulation, this study focuses on new anticoagulant agents in more advanced stages of clinical testing.

Animals↗
PubMed2003

A diagnostic strategy involving a quantitative latex D-dimer assay reliably excludes deep venous thrombosis.

BACKGROUND: Because clinical diagnosis is inaccurate, objective testing is usually considered necessary when patients present with suspected deep venous thrombosis (DVT). OBJECTIVE: To determine whether a negative result on a quantitative latex D dimer assay eliminates the need for further investigation in patients with a low or moderate pretest probability of DVT. DESIGN: Prospective cohort study. SETTING: Three tertiary care hospitals in Canada. PATIENTS: 556 consecutive outpatients with suspected first DVT. INTERVENTION: Patients were categorized as having a low, moderate, or high pretest probability of DVT and then underwent D-dimer testing. Patients with low or moderate pretest probability and a negative D-dimer result had no further diagnostic testing and received no anticoagulant therapy. Serial compression ultrasonography was performed in all other patients. Patients who did not receive a diagnosis of DVT were followed for symptomatic venous thromboembolism. MEASUREMENTS: Objectively confirmed symptomatic venous thromboembolic events during 3 months of follow-up. RESULTS: 283 patients (51%) had low or moderate pretest probability and a negative D-dimer result. One of these patients had DVT during follow-up (negative likelihood ratio, 0.05 [CI, 0.01 to 0.23]). The negative likelihood ratio of the d -dimer test in all patients was 0.03 (CI, 0.01 to 0.16). CONCLUSION: A negative result on a quantitative latex d -dimer assay safely eliminates the need for further testing in patients with low or moderate pretest probability of DVT.

Fibrin Fibrinogen Degradation Products↗
PubMed2003

Anticoagulation of pregnant women with mechanical heart valves.

The management of pregnant women with mechanical heart valves is challenging. Recently, based on small numbers of patients and poor-quality data, correspondence from Aventis Pharmaceuticals Inc has described treatment "failures" and concerns about teratogenicity with the use of the low-molecular-weight heparin (LMWH) enoxaparin. The company issued a "Warning" that enoxaparin should not be used in patients with prosthetic heart valves and a "Precaution" about potential teratogenicity. This has created a huge problem for physicians managing pregnant women with prosthetic heart valves because the alternatives, unfractionated heparin and warfarin, are problematic. There have been case reports of failures (including death from thrombosed valves) with unfractionated heparin, whereas the package insert for warfarin states that the drug is contraindicated during pregnancy because of potential teratogenicity. Initially, LMWHs appeared suitable for pregnant patients with prosthetic heart valves. Unfortunately, the company correspondence, presumably supported by the Food and Drug Administration (FDA), raises medicolegal concerns with use of any LMWH. We believe that pharmaceutical companies and the FDA should not endorse scientifically unsupported claims that eliminate acceptable therapeutic options. This correspondence has created considerable confusion among patients and treating physicians and is likely to lead to frivolous lawsuits and preclude the performance of properly designed trials in pregnant women. We believe a consensus conference among experts in the field to identify key unresolved issues and a commitment by the FDA and industry to perform appropriate studies are now critical.

Adult↗
PubMed2003

Imaging characteristics of a novel technetium Tc 99m-labeled platelet glycoprotein IIb/IIIa receptor antagonist in patients With acute deep vein thrombosis or a history of deep vein thrombosis.

BACKGROUND: The diagnosis of recurrent deep vein thrombosis (DVT) is challenging. Imaging with radiolabeled peptides offers a new approach for detecting acute DVT. Technetium Tc 99m ((99m)Tc)-apcitide binds with high affinity and specificity to the glycoprotein IIb/IIIa receptors expressed on activated platelets and, therefore, (99m)Tc-apcitide scintigraphy should be negative with residual abnormalities caused by old, inactive thrombi and positive with new, active thrombi. METHODS: In a prospective multicenter study, (99m)Tc-apcitide imaging was performed on 38 patients with a newly diagnosed first DVT (group 1) and 40 patients with previous DVT, symptoms of postthrombotic syndrome, and chronic intraluminal abnormalities on ultrasonography (group 2). Images were interpreted in a blinded fashion by 2 experts and by newly trained nuclear medicine physicians. The sensitivity and specificity of (99m)Tc-apcitide were determined by calculating the proportion of scans in group 1 patients that were read as "positive for acute DVT" and the proportion of scans in group 2 patients that were read as "negative for acute DVT," respectively. RESULTS: When read by 2 experts, ( 99m)Tc-apcitide had a sensitivity of 92% for both readers and specificities of 82% and 90%. Agreement between the experts was excellent. However, the accuracy and interreader agreement for newly trained nuclear medicine physicians were lower. CONCLUSIONS: Technetium Tc 99m-apcitide scintigraphy has potential utility in suspected recurrent DVT because it detects most acute thrombi and has few false-positive results in patients with previous DVT. However, the accuracy appears to depend on the training and experience of the interpreters.

Acute Disease↗
PubMed2002

Treatment and prophylaxis of venous thromboembolism during pregnancy.

The treatment and prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE) in pregnant patients is challenging for several reasons. Coumarins can cause embryopathy and other adverse effects in the fetus. Although unfractionated heparin and low-molecular-weight heparins, the cornerstones of initial therapy, are safe for the fetus, they can have significant maternal side effects, including osteoporosis and thrombocytopenia. Because they must be given parenterally, long-term administration is inconvenient. Further, although low-molecular-weight heparins probably cause less maternal osteoporosis and thrombocytopenia than unfractionated heparin, the appropriate dosing regimens for prevention and treatment of thrombosis during pregnancy have not been established. In addition, there is a paucity of reliable information on the incidence of venous thromboembolism and the risk of recurrent thrombosis during pregnancy. This paper briefly reviews the areas of controversy and provides recommendations for the treatment and prophylaxis of acute deep vein thrombosis and pulmonary embolism in pregnant patients.

Anticoagulants↗
PubMed2002

Low-dose warfarin in rehabilitating stroke survivors.

BACKGROUND: Patients undergoing rehabilitation after thromboembolic stroke have a relatively high incidence of venous thromboembolism (VTE). Warfarin, with a target international normalized ratio (INR) of 2.0-3.0 is effective for the prevention of VTE. However, because stroke is a major risk factor for bleeding with warfarin, a less intense regimen (target INR < 2.0), might safely prevent VTE in stroke rehabilitation patients. METHODS: This study was a randomized, double-blind, placebo-controlled trial of 2 mg of warfarin in patients undergoing rehabilitation following completed stroke. The major efficacy endpoint was symptomatic, objectively proven VTE or asymptomatic VTE detected by monthly duplex ultrasonography (DU) of the proximal leg veins or mandatory bilateral contrast venography performed at the end of the study. The major safety endpoint was bleeding. RESULTS: There were 475 patients screened for enrollment, 355 had one or more exclusion criterion, and 17 had previously undetected proximal DVT on admission. Of the 103 eligible and consenting patients, 56 received warfarin and 47 received placebo. Of the randomized patients, 88 had successful venography (47 warfarin and 41 placebo). In the warfarin group, three (8%) patients had DVT and one (2%) had proximal DVT whereas in the placebo group, seven (20%) had DVT and five (13%) had proximal DVT. The risk ratio for any DVT in warfarin-treated patients relative to placebo-treated patients was 0.39 (95% confidence interval (CI), 0.13-1.37). For proximal DVT, the risk ratio was 0.17 (95% CI, 0.01-1.4). No patients suffered major bleeding. CONCLUSIONS: A fixed dose of 2 mg of warfarin per day in patients undergoing stroke rehabilitation is safe and associated with a relative risk reduction of about 80% in the incidence of proximal DVT and 60% in overall DVT.

Adult↗
PubMed2002

How we manage venous thromboembolism during pregnancy.

During pregnancy, physiologic and anatomic changes can complicate the diagnosis of venous thromboembolism (VTE) as well as the management of patients with a high risk of or established VTE. As in nonpregnant subjects, clinical diagnosis of VTE by itself is unreliable and accurate objective testing is essential. Few diagnostic studies of VTE have been performed in pregnant women and, therefore, approaches are largely extrapolated from those used in nonpregnant subjects with modifications to limit the radiation exposure and overcome the limitations of diagnostic testing in pregnancy. Therapy of established VTE during pregnancy consists of therapeutic doses of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH), generally given throughout pregnancy subcutaneously and for 4 to 6 weeks after childbirth. A key unresolved issue includes the optimum dosing of LMWH therapy. Maternal warfarin can be safely used after childbirth because it is safe to use in the breast-fed infant of a mother receiving warfarin. Finally, pregnant women with prior VTE (with or without a hypercoagulable state) have an increased risk of recurrent venous thrombosis. A recent study has demonstrated that for women with a single episode of prior VTE, many can be managed without anticoagulants. However, for many, anticoagulant therapy with prophylactic UFH or LMWH is a reasonable option.

Anticoagulants↗