Rapid D-dimer assays to exclude deep venous thrombosis and pulmonary embolism: current status and new developments

Prevalence and Risk Factors of Deep Venous Thrombosis in Intensive Inpatient Neurorehabilitation Unit

Venous thromboembolism (VTE) (deep vein thrombosis and its complication, pulmonary embolism) is a major cause of morbidity and mortality in hospitalized patients and about 7% of these cases are due to immobility secondary to a neurological impairment. Acquired brain injury (ABI) has also been recognized as one of the main risk factors for VTE. Numerous epidemiological studies have been conducted to assess the risk factors for VTE in institutionalized polytrauma patients, although there is a lack of information about neurorehabilitation wards. Since VTE is often undiagnosed, this prospective study aimed to determine the prevalence and clinical characteristics of lower-limb deep venous thrombosis (DVT) in ABI patients at neurorehabilitation admission.

METHODS

ABI patients were screened for DVT on admission to the intensive rehabilitation unit (IRU) with compression ultrasonography and basal D-dimer assay and were daily clinically monitored until discharge. A total of 127 consecutive ABI patients (mean age: 60.1 ± 17.6 years; 63% male; time from event: 30.9 ± 22.1 days; rehabilitation time in IRU: 84.6 ± 58.4 days) were enrolled.

RESULTS

On admission to the IRU, the DVT prevalence was about 8.6%. The mean D-dimer level in patients with DVT was significantly higher than in patients without DVT (6 ± 0.9 vs. 1.97 ± 1.61, p-value = 0.0001). ABI patients with DVT did not show any significant clinical characteristics with respect to ABI without DVT, although a prevalence of hemorrhagic strokes and patients originating from the Intensive Care Unit and Neurosurgery ward was revealed. During the rehabilitation period, patients with DVT showed a significant difference in pharmacological DVT prophylaxis (high prevalence of nadroparin with 27.3% vs. 1.7%, p-value = 0.04) and a prevalence of transfers in critical awards (36% versus 9.5% of patients without DVT, p-value = 0.05). The mortality rate was similar in the two groups.

CONCLUSIONS

Our research offers a more comprehensive view of the clinical development of DVT patients and confirms the prevalence rate of DVT in ABI patients as determined upon IRU admission. According to our findings, screening these individuals regularly at the time of rehabilitation admission may help identify asymptomatic DVT quickly and initiate the proper treatment to avoid potentially fatal consequences. However, to avoid time-consuming general ultrasonography observation, a more precise selection of patients entering the rehabilitation ward is required.

Evaluation of elevated serum apelin-13 and D-dimer concentrations in individuals diagnosed with pulmonary embolism

BACKGROUND

Given the limited specificity of D-dimer, there is a perceived need to discover a more precise marker for diagnosing individuals who are suspected of having pulmonary embolism (PE). In this study, by evaluating the increase in the serum level of Apelin-13 and D-dimer, we found valuable findings about Apelin-13, which can be suggested as an auxiliary and non-invasive diagnostic biomarker in individuals with suspected PE, based on the obtained results.

METHODS

In this case-control study, 52 Iranian individuals were included, all of whom were suspected to have PE. These individuals were then divided into two groups based on the results of CT angiography, which is considered the gold standard imaging method for diagnosing PE. The two groups were patients with PE and patients without PE. Finally, the levels of certain markers in the serum were compared between the two groups.

RESULTS

The mean serum D-dimer levels in patients with PE were significantly elevated (p < 0.001) in comparison to those without PE (1102.47 to 456.2 ng/ml). Furthermore, the mean level of Apelin-13 was significantly higher in patients with PE (49.8 to 73.11 ng/L) (p < 0.001). The cutoff point of Apelin-13 has been calculated at 58.50 ng/ml, with 90.9% sensitivity and 90% specificity. The D-dimer cutoff point was 500 ng/ml, with 95.5% sensitivity and 43.3% specificity.

CONCLUSIONS

Based on the results of this study, the serum level of Apelin-13 can be used as a novel diagnostic and screening biomarker in patients with pulmonary thromboembolism.

Safe Exclusion of Deep Vein Thrombosis by a Rapid Sensitive ELISA D-dimer and Compression Ultrasonography in 1330 Outpatients With Suspected DVT

Of 1330 outpatients with suspected deep vein thrombosis (DVT), a normal enzyme-linked immunosorbent assay (ELISA) d-dimer (VIDAS) of <500 ng/mL was true negative in 382 of 384 and false negative in compression ultrasonography (CUS) in 2, indicating a sensitivity of 99.52% and a negative predictive value (NPV) of 99.48%, with a specificity of 36% irrespective of clinical score. In 1059 outpatients with no DVT, the CUS was positive for the alternative diagnoses (AD): Bakers cyst, muscle hematoma, or old DVT in 62 (5.8%); superficial vein thrombosis without DVT in 78 (7.4%), and leg edema or varices in 17%. A second CUS in 641 patients was positive in 26 (4.0%), indicating an NPV of 96% after a first negative CUS. The NPV of the combination of a negative first CUS and a ELISA d-dimer test <1000 ng/mL was 99.1% at a specificity of 66.9%. As this strategy is cost effective by reduction in the need to repeat CUS by 67%, we designed a novel algorithm for the safe exclusion and diagnosis of DVT and AD for subsequent evaluation in a large prospective study.

Impact of d-Dimers on the Differential Diagnosis of Acute Chest Pain: Current Aspects Besides the Widely Known

d-dimers are cleavage products of fibrin that occur during plasmin-mediated fibrinolysis of blood clots. In the emergency department, d-dimer measurement represents a valuable and cost-effective tool in the differential diagnosis of acute chest pain including the main life-threatening entities: acute coronary syndrome, pulmonary embolism, and acute aortic syndrome. Whereas the diagnostic and prognostic values of d-dimer testing in acute coronary syndrome is of less priority, increases of d-dimers are frequently found in venous thromboembolism and acute aortic syndromes, especially acute aortic dissection. As to the high negative predictive value of d-dimer in those disorders, patients with low to intermediate pretest probability may profit in terms of less necessity of further non-invasive or even invasive imaging, simultaneously reducing potential complications and healthcare-related costs. However, because of the low specificity of the different d-dimer tests in contrast to its frequent usage, adequate interpretation is required. Age-related adjustment of d-dimer levels may be used to increase its diagnostic power.

Value of the D-dimer test in diagnosing deep vein thrombosis in rehabilitation inpatients

OBJECTIVE

To assess the utility of the D-dimer test-a widely available, less costly, and less time-consuming test than others used to diagnose or exclude deep vein thrombosis (DVT) and pulmonary embolism.

DESIGN

Blind comparison.

SETTING

An inpatient rehabilitation facility in Turkey.

PARTICIPANTS

Sixty-eight consecutive inpatients being rehabilitated after stroke, spinal cord injury, hip arthroplasty, or traumatic brain injury.

INTERVENTIONS

A latex D-dimer assay was performed on each patient at admission and then weekly throughout the hospital stay. Color Doppler ultrasonography of the lower limbs was also done for each patient at admission and was repeated when indicated by clinical signs and symptoms of DVT or by elevated D-dimer levels. Main outcome measures Patients' clinical findings, D-dimer test results, and ultrasonography results were recorded. Sensitivity, specificity, and positive and negative predictive values were calculated for the D-dimer test, each clinical finding, and combinations of D-dimer results and clinical findings in relation to DVT diagnosis.

RESULTS

The sensitivity and negative predictive value of the D-dimer test were high, at 95.2% and 96.2%, respectively. The specificity and positive predictive value were low, at 55.3% and 48.7%, respectively. No single clinical finding was reliably diagnostic for DVT.

CONCLUSIONS

The D-dimer assay is a reliable method for ruling out DVT. In the rehabilitation setting, it can be used as a routine screening test or to assess cases of suspected DVT. D-dimer testing may reduce the need for sophisticated, time-consuming, and expensive diagnostic workup of rehabilitation inpatients, a group that is at increased risk for DVT.

Rational use of D-dimer measurement to exclude acute venous thromboembolic disease

Clinical diagnosis of venous thromboembolic (VTE) disease is often inaccurate because signs and symptoms are nonspecific. Testing for the absence of D-dimer levels in the blood of patients with suspected deep venous thrombosis and pulmonary embolism can assist in ruling out these illnesses. Some highly sensitive D-dimer assays have sufficient specificity to assist in the exclusion of VTE disease. Numerous clinical management trials using D-dimer measurement in association with additional diagnostic tests have shown that it is safe to withhold anticoagulant therapy in selected patients with suspected VTE disease who have negative D-dimer assay results. Applying these diagnostic strategies can potentially decrease the need for radiological testing. The simplicity of measuring D-dimer levels creates the potential for misuse. For safe patient management, clinicians must understand the indications for and limitations of D-dimer measurement in the diagnosis of VTE disease.

Role of fibrin D-dimer testing in emergency medicine

OBJECTIVES

Systemic values of the fibrinolytic plasma marker fibrin D-dimer are raised in a variety of acute clinical conditions. D-dimer values can now be rapidly determined and used to aid diagnosis in emergency medicine. However, despite clinical guidelines, inappropriate and unnecessary measurement of D-dimer values is a significant clinical problem. An understanding of the pathophysiological basis and limitations of the value of D-dimer values may help reduce this problem. This review discusses the pathophysiology of the fibrinolytic system. The currently used assays, clinical indications, and limitations of D-dimer measurement are reviewed. Finally, the potential future clinical indications for measurement of D-dimer values in emergency medicine are discussed.

METHODS

Literature on D-dimer was identified from Medline, along with cross referencing from the reference lists of major articles on the subject

RESULTS

and conclusions: Systemic D-dimer values aids diagnosis, and is potentially a prognostic indicator, in a variety of clinical conditions in emergency medicine. However, it has limited specificity in patients with comorbid conditions. Although, currently, there is no standard D-dimer assay, immunoturbidimetric assays are the most suitable for use in emergency medicine

Limitations of D-dimer testing in unselected inpatients with suspected venous thromboembolism

PURPOSE

To determine the utility and limitations of D-dimer testing for the evaluation of venous thromboembolism in hospitalized patients.

METHODS

We performed D-dimer testing by four different methods in unselected inpatients undergoing radiologic evaluation for possible venous thromboembolism. We included patients with a history of malignancy, recent surgery, thrombosis, and anticoagulation treatment. C-reactive protein levels were assayed as a measure of inflammation.

RESULTS

Of 45 patients with radiographically proven proximal deep venous thrombosis or pulmonary embolism, 43 had elevated D-dimer levels by enzyme-linked immunosorbent assay (ELISA) (sensitivity, 96%); the specificity of the test was 23% (36/157). The qualitative non-ELISA tests had higher specificities, but their sensitivities were <70%. Nineteen patients (42%) with thrombosis had false-negative D-dimer tests by at least one assay. The specificity of the tests decreased with increasing duration of hospitalization, increasing age, and increasing C-reactive protein levels. D-dimer testing had little or no utility in distinguishing patients with thrombosis from those without in patients who had been hospitalized for more than 3 days, were older than 60 years, or had C-reactive protein levels in the highest quartile.

CONCLUSION

In unselected inpatients, D-dimer testing has limited clinical utility because of its poor specificity. This is particularly true for older patients, those who have undergone prolonged hospitalization, and those with markedly elevated C-reactive protein levels. In some patient subsets, a negative non-ELISA D-dimer test cannot discriminate between inpatients with and without thrombosis.

Venous thromboembolism in intensive care patients

Venous thromboembolism frequently complicates the management of patients with severe medical and surgical illnesses. Because the diagnosis of VTE is especially challenging in critically ill patients, the focus of intensivists should be on characterization of risk factors and the appropriate choice of VTE prophylaxis. LDUH or LMHW is the preferred choice for VTE prophylaxis in ICU patients. Mechanical methods of prophylaxis should be reserved for patients with a high risk for bleeding. The effectiveness of mechanical methods and of combined strategies of prevention and the clinically important outcomes of therapy need to be explored further in critically ill patients. Few diagnostic strategies have been assessed in ICU patients with suspected PE. Ventilation-perfusion lung scans remain a pivotal diagnostic test but retain the same limitations in critically ill patients as seen in other patient populations. Newer noninvasive techniques, such as spiral CT associated with imaging of the extremities, are gaining more wide-spread use, but, thus far, pulmonary angiography remains the most reliable technique to confirm or exclude PE in patients with respiratory failure. A consensus must be reached regarding the most appropriate combination of tests for adequate and cost-effective diagnosis of VTE. Further investigation of diagnostic strategies that include adequate consideration of clinical diagnosis using standardized models and noninvasive imaging are warranted.

Can a state-of-the-art D-dimer test be used to determine the need for CT imaging in patients suspected of having pulmonary embolism?

RATIONALE AND OBJECTIVES

The purpose of this study was to determine whether a simple rapid blood test can obviate computed tomography (CT) in a sizable percentage of patients suspected of having pulmonary embolism, based on the hypothesis that negative D-dimer results could eliminate any further search for pulmonary embolism.

MATERIALS AND METHODS

At the authors' institution, 2,121 sequential patients underwent a whole-blood antibody agglutination test for cross-linked fibrin degradation products (D-dimer). Of these patients, 844 had positive test results and were not further considered. A retrospective review included reports of all multisection combined CT venographic and pulmonary angiographic studies obtained within 48 hours of the D-dimer assay for the 1,277 patients with negative D-dimer results; 229 (18%) of these 1,277 patients underwent combined CT venography and pulmonary angiography, usually within 24 hours.

RESULTS

Retrospective review of the imaging examinations that were discrepant with the D-dimer results revealed only three false-negative D-dimer results. Of the 229 patients in whom combined CT venography and pulmonary angiography was performed for suspected pulmonary embolism, 226 (98.7%) had no evidence of acute pulmonary embolism or deep venous thrombosis. The negative predictive value of a negative D-dimer result was therefore 98.7% (confidence interval, 96.2%-99.7%).

CONCLUSION

The D-dimer assay is a simple rapid blood test that is sensitive to the presence of acute thrombosis. Very few patients with negative results have acute deep venous thrombosis or pulmonary embolism, with combined CT venography and pulmonary angiography used as the reference standard.

The accuracy of the enzyme-linked immunosorbent assay D-dimer test in the diagnosis of pulmonary embolism: a meta-analysis

STUDY OBJECTIVE

We sought to determine the sensitivity and specificity of the enzyme-linked immunosorbent assay (ELISA) D -dimer test in the diagnosis of pulmonary embolism (PE) in the adult emergency department population.

METHODS

A search of MEDLINE, EMBASE, and bibliographies of previous systematic reviews was conducted, with no language restriction. Experts in the field of PE research were contacted to identify unpublished studies. Prospective investigations involving a predominately outpatient population suspected of PE that used ELISA D -dimer tests were included. Two authors extracted data independently and assessed study quality on the basis of the patient spectrum and reference standard. Consensus was reached by means of conference. The analysis was based on a summary receiver operating characteristic curve and pooled estimates for sensitivity and specificity by using a random-effects model.

RESULTS

The search yielded 52 publications. No unpublished studies were found. Eleven studies met the inclusion criteria and provided a sample of 2,126 patients. The summary receiver operating characteristic curve analysis found significant heterogeneity among the 11 studies. Subgroup analysis of the 9 studies that used traditional ELISA D -dimer methods yielded the most valid pooled estimates, with a sensitivity of 0.94 (95% confidence interval [CI] 0.88 to 0.97) and a specificity of 0.45 (95% CI 0.36 to 0.55). Advanced age resulted in a lower specificity. A prolonged duration of symptoms decreased the sensitivity and specificity.

CONCLUSION

The ELISA D -dimer test is highly sensitive but nonspecific for the detection of PE in the clinical setting. This test might help clinicians safely rule out PE, especially in the face of low and low-to-moderate pretest probabilities.

[Diagnostic value of D-dimer in patients with a low pretest probability of deep venous thrombosis of lower extremities]

BACKGROUND

We aimed to assess the accuracy of a diagnostic strategy including broth clinical assessment and determination of D-dimer (DD) in patients with clinically suspicion of low pretest probability of deep venous thrombosis (DVT).

METHOD

149 outpatients (mean age 69; SD 16) with clinically suspected proximal DVT attending our Emergency Department and classified as low pretest probability were included in an observational prospective study. In patients with a DD (STA Liatest D-Di, Diagnostica Stago, Asnières sur Seine, France) concentration below the cut-off value (0.4 ng/ml) the diagnosis of DVT was readily ruled out, whereas those individuals with a positive DD result underwent compression Doppler venous ultrasound. A 3-month clinical follow-up was carried out in those patients in whom a diagnosis of DVT was initially excluded.

RESULTS

Only 2 cases of DVT were confirmed (prevalence 1.3%; CI 95%, 0.2-5.3). In 47.6% of cases, a DD negativity ruled out the diagnosis of DVT. The rate of negative DD results was significantly lower in patients below 70 years of age as compared to older patients (73.6 versus 33.3%) (p < 0.001). Sensitivity, specificity, positive predictive value and negative predictive value of DD in our series were 100% (CI 95%,19.7-95.1), 48.3% (CI 95%, 40.0-56.7), 2.6% (CI 95%, 0.4-9.8) and 100% (CI 95%, 93.6-99.8) respectively, the latter being similar in the two age groups. No case of DVT was diagnosed during the follow-up period.

CONCLUSIONS

In patients with a low pretest probability of DVT a negative DD result reliably and safely rules out such diagnosis. However, the diagnostic value of DD is lower in elderly patients (>= 70 years of age) due to a lower rate of negative results in these individuals.

Major pulmonary embolism: review of a pathophysiologic approach to the golden hour of hemodynamically significant pulmonary embolism

Major pulmonary embolism (PE) results whenever the combination of embolism size and underlying cardiopulmonary status interact to produce hemodynamic instability. Physical findings and standard data crudely estimate the severity of the embolic event in patients without prior cardiopulmonary disease (CPD) but are unreliable indicators in patients with prior CPD. In either case, the presence of shock defines a threefold to sevenfold increase in mortality, with a majority of deaths occurring within 1 h of presentation. A rapid integration of historical information and physical findings with readily available laboratory data and a structured physiologic approach to diagnosis and resuscitation are necessary for optimal therapeutics in this "golden hour." Echocardiography is ideal because it is transportable, and is capable of differentiating shock states and recognizing the characteristic features of PE. Spiral CT scanning is evolving to replace angiography as a confirmatory study in this population. Thrombolytic therapy is acknowledged as the treatment of choice, with embolectomy reserved for those in whom thrombolysis is contraindicated.

Current strategies for the diagnosis of pulmonary embolus

Venous thromboembolic disease (VTD), comprising venous thrombosis and pulmonary embolus, is responsible for innumerable deaths every day. Wide variance in its presentation and clinical manifestations and the resultant difficulties in achieving its diagnosis have confounded attempts to define optimal diagnostic and treatment strategies. Those strategies should be predicated on the understanding of the manifestations of VTD and of the attributes and interrelationship of the various modalities available for its diagnosis. This review will present an overview of the literature describing those modalities, their strengths and deficiencies, and their current value in algorithms for the diagnosis of VTD.

The diagnosis of lower extremity deep venous thrombosis

The diagnosis of lower extremity deep venous thrombosis (DVT) is critical to emergency physicians because of the risk of pulmonary embolism. This article reviews the diagnostic modalities available for patients with suspected lower extremity DVT. The use of compression ultrasonography and the recent advances in the D-dimer assays are emphasized. A clinical algorithm that utilizes a non invasive approach to this potentially life threatening disease is presented.

Pulmonary embolism: making sense of the diagnostic evaluation

Despite the publication of the Prospective Investigation of Pulmonary Embolism Diagnosis in 1990, the diagnostic evaluation of pulmonary embolism continues to be approached in an inconsistent fashion. The reasons for this are unclear but likely have to do with inadequate methods for predicting pretest probability of disease and the inconvenience and perceived risk of pulmonary angiography. Because pulmonary embolism and its treatment carry substantial risk of morbidity and mortality, a consistent approach to evaluation is desirable. This article reviews large, prospective studies that suggest that it may be unnecessary to diagnose pulmonary embolism with the certainty that pulmonary angiography allows. Finally, the article proposes an algorithm that may be acceptable to patients and clinicians alike if safety is confirmed in future prospective studies.

Improving detection of venous thromboembolism. New technology holds promise for early, precise diagnosis

In recent years, a number of modalities have been evaluated for the diagnosis of venous thromboembolism. The role of these modalities is still evolving. While ventilation-perfusion scanning is important in the diagnosis of venous thromboembolism, spiral CT scanning, MRI, and D-dimer assays are now being used more often, either exclusively or in combination with ventilation-perfusion scanning. A number of diagnostic algorithms using these modalities are currently being evaluated. Regardless of which diagnostic approach is used, the clinician must be aware of some key limitations. Spiral CT scanning has gained popularity because it is noninvasive and can rapidly identify other cardiopulmonary diseases that mimic pulmonary embolism. Its use has been limited because of its inability to detect subsegmental pulmonary emboli. D-dimer assays offer promise as rapid, inexpensive screening tools. However, the wide variability in assay performance has limited its usefulness. We recommend that if D-dimer assays are to be used in a diagnostic algorithm, the clinician be aware of the details of the assay. At present, lack of data precludes use of MRI as a primary diagnostic tool for detection of venous thromboembolism.

Diagnosis of venous thromboembolism. Step-by-step approach to a still lethal disease

Rapid diagnosis of VTE is vital in reducing the significant morbidity and mortality rates associated with this disease. Although angiographic studies remain the "gold standard" for diagnosis, many noninvasive diagnostic procedures are available and are appropriate for evaluation in clinically stable patients. The algorithm presented in this article facilitates the practical and efficient use of available resources in diagnosing and treating VTE.

Exclusion and diagnosis of deep vein thrombosis by a rapid ELISA D-dimer test, compression ultrasonography, and a simple clinical model

The classical clinical signs of deep vein thrombosis (DVT) are unspecific and may be found in several other conditions besides DVT. Therefore, patients suspicious of DVT are subjected to elaborate invasive or noninvasive evidence-based procedures that actually confirm DVT in only 20% to 30% of patients in this setting. However, simple laboratory tests and noninvasive strategies to exclude and diagnose DVT are becoming available in the clinical emergency setting of outpatients. In the presented literature, a sound basis is provided for quantifying clinical judgment for the diagnosis of acute proximal DVT. The number of positive clinical findings at time of first suspicion of DVT appears to correlate directly with the probability of acute proximal DVT. The modified clinical model of Landefeld and Wells for DVT allows reasonable accurate classification of patients into low, moderate, and high probability for suffering DVT. The rapid automated enzyme-linked immunoabsorbant assay (ELISA) VIDAS D-dimer presently available can be rapidly performed in daily practice and emergency situations and is accurate to a high degree, especially in ruling out ongoing venous thromboembolic processes. The sequential use of the rapid ELISA VIDAS D-dimer test and compression ultrasonography in a well-designed clinical setting using a simple clinical model predicts a significant improvement due to a high sensitivity near 100% for the exclusion and diagnosis of DVT in the majority of outpatients with suspect DVT. A prospective decision analysis management study is proposed to exclude and diagnose DVT based on the rapid ELISA VIDAS D-dimer test and compression ultrasonography within the context of a ready-to-use simple clinical model. The proposed simple model of a rational diagnosis of deep vein thrombosis (RADIA DVT) has to be tested in a large multicenter study of more than 1,000 outpatients with suspected DVT. This model would be less expensive, easy to perform, and likely yield a significant simplification and improvement of highly accurate evidence-based exclusion or diagnosis of DVT on the basis of which clear-cut indications of anticoagulation could be appropriately initiated or safely withheld.