D-dimer plasma concentration in various clinical conditions: implication for the use of this test in the diagnostic approach of venous thromboembolism

Perioperative Deep Vein Thrombosis and D-dimer Measurement in Patients with Brain Tumor

We investigated the appropriate D-dimer cutoff value for each brain tumor type for acute or subacute deep vein thrombosis (DVT) following transcranial brain tumor surgery.In this single-center retrospective study, a cumulative total of 128 patients who underwent transcranial brain tumor surgery were enrolled and classified into the glioma group, the other intracranial malignant tumor group, and the intracranial benign tumor group. Venous ultrasonography was performed if the D-dimer plasma levels were positive (≥1 μg/mL) before surgery and on postoperative day (POD) 3 or 7.Of the 128 cases, DVT developed in 32 (25.0%). Among those, acute or subacute DVT was diagnosed in 22 cases on POD 3 and in 8 cases on POD 7. Compared with DVT-negative cases on POD 3, acute or subacute DVT-positive cases on POD 3 revealed a significant increase in the D-dimer level in all groups combined and in the benign tumor group but not in the glioma group. With regard to DVT on POD 3 in all groups, the receiver operating characteristic curve for the D-dimer level on POD 3 demonstrated a cutoff value of 3.3 μg/mL (sensitivity [0.636] and specificity [0.750]). However, if this cutoff value was used in practice, eight cases would be false-negative with a minimum D-dimer level of 1.5 μg/mL.The D-dimer cutoff value for acute or subacute DVT on POD 3 could be set to 3.3 μg/mL; however, the setting resulted in several false-negative cases. Practically, 1.5 μg/mL of the D-dimer cutoff value on POD 3 might be appropriate to avoid false-negative results.

Order Indication Solicitation to Assess Clinical Laboratory Test Utilization: D-Dimer Order Patterns as an Illustrative Case

Background:

A common challenge in the development of laboratory clinical decision support (CDS) and laboratory utilization management (UM) initiatives stems from the fact that many laboratory tests have multiple potential indications, limiting the ability to develop context-specific alerts. As a potential solution, we designed a CDS alert that asks the ordering clinician to provide the indication for testing, using D-dimer as an exemplar. Using data collected over a nearly 3-year period, we sought to determine whether the indication capture was a useful feature within the CDS alert and whether it provided actionable intelligence to guide the development of an UM strategy.

Methods:

We extracted results and ordering data for D-dimer testing performed in our laboratory over a 35-month period. We analyzed order patterns by clinical indication, hospital service, and length of hospitalization.

Results:

Our final data set included 13,971 result-order combinations and indeed provided actionable intelligence regarding test utilization patterns. For example, pulmonary embolism was the most common emergency department indication (86%), while disseminated intravascular coagulation was the most common inpatient indication (56%). D-dimer positivity rates increased with the duration of hospitalization and our data suggested limited utility for ordering this test in the setting of suspected venous thromboembolic disease in admitted patients. In addition, we found that D-dimer was ordered for unexpected indications including the assessment of stroke, dissection, and extracorporeal membrane oxygenation.

Conclusions:

Indication capture within a CDS alert and correlation with result data can provide insight into order patterns which can be used to develop future CDS strategies to guide appropriate test use by clinical indication.

Inappropriate use of D-dimer and impact on the test characteristics for deep vein thrombosis exclusion

This study aimed to investigate the prevalence of the inappropriate use of D-dimer testing for deep vein thrombosis (DVT) exclusion, and to evaluate the diagnostic value of D-dimer testing compared between testing in appropriate and inappropriate conditions. A retrospective chart review of patients with D-dimer requests at Siriraj Hospital, Bangkok, Thailand during January-September 2017 was performed. Data relating to D-dimer requests, Wells score, imaging investigations, and coexisting conditions that cause elevated D-dimer without correlation to DVT were analyzed. From 2196 cases, there were 300 D-dimer requests for DVT diagnosis. Of those, 5 (1.7%) and 158 (53.6%) requests were considered to be absolutely inappropriate D-dimer test requests due to the absence of pre-test Wells score evaluation and testing in DVT-likely patients, respectively. One-hundred and forty-eight (49.3%) requests were considered to be the relatively inappropriate D-dimer test requests due to testing in patients with coexisting conditions that included malignancies, sepsis, surgery, trauma, arterial thrombosis, and pregnancy. Three patients had more than one of these conditions. Comparatively higher negative predictive values (NPVs) of D-dimer assay for DVT exclusion were observed when used in DVT-unlikely (100% versus 80%), and in patients without coexisting conditions (100% versus 66.7%). The present study revealed the rate of inappropriate D-dimer testing for DVT exclusion to be high and this may lead to missed DVT diagnosis, overuse of imaging study, and unnecessary cost of D-dimer testing. Appropriate patient selection before test request can improve the NPV of D-dimer for DVT exclusion.

D-dimer value in the diagnosis of pulmonary embolism-may it exclude only?

Background

Pulmonary embolism (PE) is the third most common cause of death for cardiovascular diseases in Europe. Quick PE diagnosis is therefore crucial for prognosis improvement. It is critical to have suitable screening tests both to exclude PE as well to select patient with highest likelihood of PE occurrence. Currently D-dimer test is accepted as important tool useful to exclude PE in low risk patients. Our goal was to assess the D-dimer test positive prognostic value.

Methods

A retrospective study based on medical record analysis of consecutively admitted patients to 9 wards of The University Clinical Center in Katowice who were hospitalized during four consecutive years was performed. Three hundred and seventy patients met the inclusion criteria for the study, which involved the D-dimer tests and computed tomographic pulmonary angiography (CTPA) performed during hospitalization. Assessed patients were divided into two groups: PE confirmed and PE excluded by CTPA.

Results

We have found that patients with D-dimer levels higher than 2,152 ng/mL had significantly increased risk of PE [area under curve (AUC) of 0.69; 95% CI, 0.64-0.75; P<0.05]. Positive predictive value (PPV) reached the level of 53%, whereas negative predictive value (NPV) reached 82%. We also found that patients with the history of neoplasm and at >65 years of age had D-dimer cut-off point moved to the level of 2,652 ng/mL (AUC of 0.67; 95% CI, 0.52-0.81; P<0.05).

Conclusions

Whereas the NPV of the D-dimer test is generally accepted our results suggest that, in selected cases, an increased plasmatic D-dimer levels may have PPV in PE diagnosis. Patients with the history of neoplasm have higher cut-off D-dimer points above which we should consider increased PE likelihood. CTPA should be considered even for patients with low probability of PE when D-dimer values exceed four times the normal level.

Effects of impaired renal function on levels and performance of D-dimer in patients with suspected pulmonary embolism

Clinical probability and D-dimer measurement play an essential role in the non-invasive diagnostic strategies for pulmonary embolism (PE). PE can be ruled out without further imaging in patients with non-high clinical probability and negative D-dimer. D-dimer level is increased in patients with renal impairment. Whether its diagnostic usefulness is maintained in these patients is not well determined. We aimed to evaluate the effects of renal impairment on diagnostic performances of D-dimer in patients with suspected PE. A retrospective analysis of 1,625 patients with suspected PE included in a multicentre prospective study was performed. D-dimer levels and percentages of patients with a negative D-dimer were compared between three subgroups according to glomerular filtration rate (GFR) estimated by the MDRD formula: ≥90 ml/min (normal renal function), 60–89 ml/min (mild renal impairment), 30–59 ml/min (moderate renal impairment). D-dimer levels increased and the proportion of negative D-dimer decreased significantly according to renal status: 46% negative D-dimer in patients with normal GFR, 31% in patients with mild renal impairment, 11% in those with moderate renal impairment, corresponding to number of patients needed to test to obtain one negative test of 2.2, 3.2 and 9, respectively. In conclusion, the clinical usefulness of D-dimer decreases with renal impairment. However, PE can still be ruled out by negative D-dimer in a substantial proportion of patients with non-high clinical probability, avoiding exposure to contrast media.

Screening for Pulmonary Embolism with a D-Dimer Assay: Do we Still Need to Assess Clinical Probability as Well?

Clinical risk stratification and D-dimer assay can be of use in excluding pulmonary embolism in patients presenting to emergency departments but many D-dimer assays exist and their accuracy varies. We used clinical risk stratification combined with a quantitative latex-agglutination D-dimer assay to screen patients before arranging further imaging if required. Retrospective analysis of a sequential series of 376 patients revealed that no patient with a D-dimer of <275 ng/mL was diagnosed with pulmonary embolism, irrespective of clinical probability. We conclude that a latex-agglutination assay could be used to exclude pulmonary embolism without the necessity for clinical risk stratification. If these findings are borne out by further work, D-dimer strategies to exclude pulmonary embolism could substantially reduce imaging workload.

Diagnosis of deep-vein thrombosis

The diagnostic approach to suspected symptomatic deep-vein thrombosis of the lower extremities is usually based on non-invasive methods, including the estimation of clinical probability, the measurement of D-dimer levels, and ultrasonography. The present review discusses the evidence available from the literature about the management of the first episode of suspected deep-vein-thrombosis.

Effects of Oritavancin on Coagulation Tests in the Clinical Laboratory

Previous studies have shown that some lipoglycopeptide and lipopeptide antimicrobial agents may cause falsely elevated values for some phospholipid-dependent coagulation tests. The effect of oritavancin, a lipoglycopeptide antibiotic, on coagulation test results was explored using pooled human plasma samples spiked with drug and in a clinical study after an infusion of a single 1,200-mg intravenous dose of oritavancin in normal healthy volunteers. Pooled plasma with oritavancin added ex vivo showed concentration-dependent prolongation of prothrombin time/international normalized ratio (PT/INR), activated partial thromboplastin time (aPTT), and dilute Russell viper venom time (DRVVT) test results. In contrast, oritavancin had no effect on the activated protein C resistance assay, chromogenic anti-factor Xa assay (anti-FXa), thrombin time, and an immunoassay for the laboratory diagnosis of heparin-induced thrombocytopenia. In participants that received a single dose of oritavancin, elevations in PT/INR result, aPTT, DRVVT, activated clotting time, and silica clotting time occurred, with the maximum times to resolution of test interference determined to be 12, 120, 72, 24, and 18 h, respectively. The anti-FXa assay was unaffected, whereas transient elevations in D dimer levels were observed in 30% of participants, with a maximum time to resolution of 72 h. Although oritavancin has no impact on the coagulation system in vivo, a single dose of oritavancin can produce falsely elevated values of some coagulation tests used to monitor hemostasis. The interference of oritavancin on affected tests is transient, and the test results revert to normal ranges within specified times after dosing.

d-Dimer as a Screening Marker for Venous Thromboembolism After Surgery Among Patients Younger Than 50 With Lower Limb Fractures

OBJECTIVE

For the present study, the authors hypothesized that the d-dimer levels would be systematically raised in a postoperative population of patients younger than 50 with lower limb fractures and to define a feasible cutoff value for identification of venous thromboembolism (VTE).

METHODS

Doppler ultrasonography of lower limbs was performed pre- and postoperatively to evaluate for deep vein thrombosis in 150 patients who underwent open reduction and internal fixation (ORIF). Plasma d-dimer levels were assessed 2 days before surgery and on the 3rd, 7th, and 10th days after surgery. Statistical analysis was carried out to define a feasible threshold for the d-dimer levels.

RESULTS

Plasma d-dimer levels were found to be systematically raised postoperatively, and they differed between patients with and without VTE significantly. On the third day after surgery, d-dimer levels of more than 3 mg/L indicated VTE with a sensitivity of 88.37% and a specificity of 96.96%, allowing for the definition of a feasible cutoff value. Duration of surgery, duration of tourniquet, ventilation time, and time of postoperative immobility of lower limbs were identified as highly significant risk factors for the development of VTE.

CONCLUSION

Using a threshold of 3 mg/L, the d-dimer levels will screen out VTE with a high degree of sensitivity and specificity in younger patients who have undergone ORIF for lower limb fractures.

D-dimer plasma level: a reliable marker for venous thromboembolism after elective craniotomy

OBJECT

The incidence of deep venous thrombosis (DVT) after craniotomy is reported to be as high as 50%. In outpatients, D-dimer levels of more than 0.5 mg/L indicate venous thromboembolism (VTE, which subsumes DVT and pulmonary embolism [PE]) with a sensitivity of 99.4% and a specificity of 38.2%. However, D-dimer levels are believed to be unreliable in postoperative patients. The authors undertook the present study to test the hypothesis that D-dimer levels would be systematically raised in a postoperative population and to define a feasible threshold for identification of VTE.

METHODS

Doppler ultrasonography of the lower extremity was performed pre- and postoperatively to evaluate for DVT in 101 patients who underwent elective craniotomy. D-dimer levels were assessed preoperatively and on the 3rd, 7th, and 10th days after surgery. Statistical analysis was carried out to define a feasible threshold for D-dimer levels.

RESULTS

D-dimer plasma levels were found to be systematically raised postoperatively, and they differed between patients with and without VTE in a highly significant way. On the 3rd day after surgery, D-dimer levels of more than 2 mg/L indicated VTE with a sensitivity of 95.3% and a specificity of 74.1%, allowing for the definition of a feasible threshold. D-dimer levels of more than 4 mg/L were observed in all patients who had PE during the postoperative period (n = 9). Ventilation time and duration of surgery were identified as highly significant risk factors for the development of VTE.

CONCLUSIONS

Using a threshold of 2 mg/L, D-dimer levels will indicate VTE with a high degree of sensitivity and specificity in patients who have undergone craniotomy. Pulmonary embolism seems to be indicated by even higher D-dimer levels. Given that the development of D-dimer plasma levels in the postoperative period follows a principle that can be predicted and that deviations from it indicate VTE, this principle might be applicable to other types of surgery.

Specificity of quantitative latex agglutination assay for D-dimer in exclusion of pulmonary embolism in the emergency department

We assessed the prevalence of elevated quantitative latex agglutination assay for D-dimer in patients in the emergency department in whom pulmonary embolism (PE) was excluded. D-dimer was normal (<230 ng/mL) in 435 (83%) of the 522 patients. D-dimer was normal in 88% of the patients with musculoskeletal or related chest pain, 74% with pleurisy or pleuritic chest pain, and 85% with upper respiratory tract infection. D-dimer was 230 to 500 ng/mL in 65 (75%) of the 87 in whom D-dimer was elevated. Clinical probability was low in 31 (48%) of the 65 patients with D-dimer levels of 230 to 500 ng/mL. D-dimer was 230 to 500 ng/mL and clinical probability was low in 31 (36%) of the 87 patients who had computed tomographic (CT) angiograms because of elevated D-dimer. Negative likelihood ratio for PE is sufficiently low that PE can be excluded with reasonable certainty in such patients. Tailoring cutoff value to 500 ng/mL in patients with low clinical probability would have reduced CT angiograms by 36%.

N-terminal prohormone of brain natriuretic peptide: a useful tool for the detection of acute pulmonary artery embolism in post-surgical patients

BACKGROUND

Acute pulmonary embolism (APE) is an important clinical problem in patients after major surgery and often remains a difficult diagnosis because of unspecific clinical symptoms. Therefore, we investigated the role of N-terminal prohormone of brain natriuretic peptide (NT-proBNP) for the detection of APE.

METHODS

In 44 patients with suspected APE referred to the intensive care unit after major surgery, serum NT-proBNP, troponin-I, and D-dimers were measured according to the standard hospital protocol. To definitively confirm or exclude APE, all patients underwent an angiographic CT scan of the thorax.

RESULTS

APE was confirmed in 28 and excluded in 16 patients by CT scan. NT-proBNP was significantly (P<0.01) higher in patients with APE [4425 (sd 8826; range 63-35 000) pg ml(-1)] compared with those without [283 (sd 327; range 13-1133) pg ml(-1)]. The sensitivity of the NT-proBNP screening was 93%, specificity 63%, positive predictive value 81%, and negative predictive value 83%. There were no significant (P = 0.96) differences in D-dimers between subjects with and without APE [confirmed APE: 511 (sd 207; range 83-750) μg litre(-1); excluded APE: 509 (sd 170; range 230-750) μg litre(-1)]. Troponin-I levels were not elevated in 32% of the patients with APE.

CONCLUSIONS

D-dimer levels are frequently elevated in post-surgical patients and not applicable for confirmation or exclusion of APE. In contrast, NT-proBNP appears to be a useful biomarker for APE diagnosis in the postoperative setting. In the case of NT-proBNP levels below the upper reference limit, haemodynamically relevant APE is unlikely. Troponin-I in contrast is not considered to be helpful.

The diagnostic value of D-dimer, procalcitonin and CRP in acute appendicitis

BACKGROUND

The early diagnosis of acute abdomen is of great importance. To date, several inflammatory markers have been used for the diagnosis of acute abdominal conditions, including acute appendicitis. The aim of this study was to evaluate the diagnostic utility of D-dimer, Procalcitonin (PCT) and C-reactive protein (CRP) measurements in the acute appendicitis.

METHODS

This prospective study was conducted between March 1(st), 2010 and July 1(st), 2011. In this period, seventy-eight patients were operated with the diagnosis of acute appendicitis, and D-dimer, PCT and CRP levels of the patients were measured. The patients were grouped as phlegmonous appendicitis (Group 1), gangrenous appendicitis (Group 2), perforated appendicitis (Group 3) and negative appendectomy (Group 4) according to the surgical findings and histopathological results.

RESULTS

Of 78 patients, 54 (69.2 %) were male and 24 (30.8 %) were female, and the mean age was 25.4 ± 11.1 years (range, 18 to 69 years). 66 (84.6 %) patients had increased leukocyte count (white blood cell count). The PCT values were higher than the upper normal limit in 20 (25.6%) patients, followed by D-dimer in 22 (28.2 %) patients and CRP in 54 (69.2 %) patients. The diagnostic value of leukocyte count and CRP in acute appendicitis was higher than that of the other markers, whereas leukocyte count showed very low specificity. CRP values were higher in perforated appendicitis when compared with the phlegmonous appendicitis (p < 0.05). However, PCT and D-dimer showed lower diagnostic values (26% and 31%, respectively).

CONCLUSION

An increase in CRP levels alone is not sufficient to make the diagnosis of acute appendicitis. However, CRP levels may differentiate between phlegmonous appendicitis and perforated appendicitis. Due to their low sensitivity and diagnostic value, PCT and D-dimer are not better markers than CRP for the diagnosis of acute appendicitis.

The modified Wells score accurately excludes pulmonary embolus in hospitalized patients receiving heparin prophylaxis

BACKGROUND

The usefulness of the Wells score has not been assessed in hospitalized patients receiving prophylactic heparin.

METHODS

Retrospective, observational study of hospitalized patients receiving prophylactic heparin who underwent contrast-enhanced chest computed tomography (CT) for a concern of pulmonary embolism (PE) more than 2 days after admission. Patients with contraindications to, or interruptions in, prophylactic heparin were excluded. The modified (eg, dichotomous) Wells score was retrospectively calculated by reviewing each patient's record. Requesting a D-dimer was taken to mean that alternate diagnoses were of equal or greater likelihood than acute PE.

RESULTS

From January 2006 through December 2007, 286 patients met inclusion criteria. Pulmonary embolus diagnosed by CT was present in 20 patients (7%). The sensitivity, specificity, positive and negative predictive values of a Wells score ≥4.0 were 95%, 27%, 9% and 99%, respectively. A D-dimer was ordered in 70 of the 74 PE-unlikely cases, was elevated in 67, and falsely positive in all but 1.

CONCLUSIONS

The prevalence of PE in hospitalized patients receiving prophylactic heparin is lower than in cohorts from which the Wells prediction criteria were derived and validated. A modified Wells score <4 safely excludes PE in such patients and reduces the need for CT. D-dimer testing adds nothing to the evaluation.

Cost-effective diagnostic strategies in patients with a high, intermediate, or low clinical probability of pulmonary embolism

Rapid quantitative D-dimer assays (DD), lower extremity venous duplex ultrasonography (US), and multislice computed tomographic (CT) angiography have been shown to have adequate sensitivities and specificities for diagnostic purpose. The purpose of this study was to evaluate cost-effectiveness of diagnostic strategies for pulmonary embolism (PE) in patients with a high, intermediate, or low clinical probability of PE. A formal cost-effectiveness analysis for the diagnosis of PE was performed. The main outcome measure for effectiveness was 3-month expected survival. The strategy of DD followed by CT was cost-effective and had the lowest cost per life saved for all patients suspected with PE. The conventional strategy including ventilation and perfusion lung scanning followed by pulmonary angiography (PA) or CT was not cost-effective. The leg US after CT was not also cost-effective. In clinical practice, the individual patient's condition should be considered when choosing appropriate diagnostic tests.

Appropriate use of D-dimer in hospital patients

D-dimer, the final product of plasmin-mediated degradation of fibrin-rich thrombi, has emerged as a simple blood test that can be used in diagnostic algorithms for the exclusion of venous thromboembolism. D-dimer also is used as a part of the diagnostic tests for disseminated intravascular coagulation, where excessive thrombin generation is the key pathophysiological factor. However, there are no robust data available at present on the use of this test to exclude venous thromboembolism in a hospital inpatient. Considerable confusion also exists among physicians about its appropriate use and interpretation in disseminated intravascular coagulation. This article focuses on the available evidence to guide the appropriate use of D-dimer in patients admitted to a hospital.

The use of D-dimer in specific clinical conditions: a narrative review

The use of D-dimer in combination with a clinical decision rule has been widely investigated in pulmonary embolism and deep venous thrombosis. Although it has been shown to be safe in excluding venous thromboembolism, the clinician is often faced with specific situations in which the use of D-dimer is controversial. We review the best available evidence on these patients. We conclude that it is not safe to use D-dimer testing in patients with symptoms of a venous thromboembolism for over 14 days, patients receiving therapeutic heparin treatment and patients with suspected deep venous thrombosis during oral anticoagulant therapy. In these populations the levels of D-dimer can be lower then expected giving rise to false-negative results. It is safe to use D-dimer testing in combination with a clinical decision rule in patients of all ages, patients presenting with a suspected recurrent venous thromboembolism or inpatients with suspected pulmonary embolism. As patients with recurrent venous thromboembolism, elderly patients and inpatients have higher levels of D-dimer, D-dimer testing has a low specificity and the need for additional radiological testing is increased.

D-Dimer for venous thromboembolism diagnosis: 20 years later

Twenty years after its first use in the diagnostic workup of suspected venous thromboembolism (VTE), fibrin D-dimer (DD) testing has gained wide acceptance for ruling out this disease. The test is particularly useful in the outpatient population referred to the emergency department because of suspected deep vein thrombosis (DVT) or pulmonary embolism (PE), in which the ruling out capacity concerns every third patient clinically suspected of having the disease. This usefulness is based on the high sensitivity of the test to the presence of VTE, at least for some assays. Due to its poor specificity precluding its use for ruling in VTE, DD testing must be integrated in comprehensive, sequential diagnostic strategies that include clinical probability assessment and imaging techniques such as lower limb venous compression ultrasonography for suspected DVT or multi-slice helical computed tomography for suspected PE. The present narrative review updates the data available on the use of the various commercially available DD assays in the diagnostic approach of clinically suspected VTE in distinct patient populations or situations, including outpatients and inpatients, patients with cancer, older age, pregnancy, a suspected recurrent event, limited thrombus burden, and patients already on anticoagulant treatment.

Laboratory testing in the intensive care unit

Laboratory testing is ubiquitous among hospitalized patients and is more common among patients in the intensive care unit (ICU). Despite its high cost and prevalence, there are few data to support the current practice of laboratory testing in most ICUs. Although testing offers considerable potential benefits, it is not without risk, including misleading results, iatrogenic anemia, and therapeutic actions of uncertain benefit. Laboratory testing should be conducted as part of a therapeutic approach to a clinical problem, mindful of pretest probability of disease, the performance of the selected test, and the relative benefits and risks of testing. Considering the indication for a particular test can lead to a more rational approach to laboratory testing and better use of available tests.

Diagnostic accuracy of the Triage® D-dimer test for exclusion of venous thromboembolism in outpatients

BACKGROUND

We evaluated the diagnostic performance of the Triage D-dimer test, a new fast quantitative point-of-care whole blood D-dimer assay and compared it with the Vidas D-dimer assay.

MATERIALS AND METHODS

The study population comprised 319 outpatients for whom D-dimer testing was requested in order to rule out venous thromboembolism (VTE). Routine testing consisted of a plasma ELISA D-dimer analysis (Vidas). For all included patients, an additional EDTA whole blood D-dimer test (Triage) was performed. Patients were classified by reference imaging or by follow-up of the medical record. Accuracy indices, receiver operating characteristics and the kappa coefficient for agreement were calculated using the cutoff values recommended by the manufacturer.

RESULTS

Prevalence of VTE was 14%. Sensitivity and specificity for VTE were 98% (95%CI: 88-100) and 34% (95%CI: 28-40) for Vidas and 91% (95%CI: 78-97) and 42% (95%CI: 36-48) for Triage, respectively. The differences in sensitivity and specificity between both D-dimer assays were statistically significant (McNemar, p<0.0001). ROC-curve analysis yielded an area under the curve of 0.83 (95%CI: 0.76-0.89) for the Vidas and 0.81 (95%CI: 0.74-0.88) for the Triage (p=0.396). The kappa coefficient for agreement between Vidas and Triage was 0.75 (95%CI: 0.68-0.79).

CONCLUSIONS

The Triage and Vidas D-dimer tests show comparable diagnostic accuracy. Vidas showed a significant higher sensitivity. Our findings strongly suggest lowering the cutoff for the Triage D-dimer test from 400 to 350 ng/mL. In this way specificity lowers from 42 to 38%, but, more importantly, sensitivity increases from 91 to 95%.

[Deep-vein thrombosis despite a low D-Dimer level]

OBJECTIVE

Deep-vein thrombosis is common but not easy to diagnose. It is generally considered that the diagnosis can be ruled out in subjects with a D-Dimer level lower than a reference threshold value. We report a case where this hypothesis was misleading.

METHOD

An 89-year-old man was hospitalized for a pain in his left lower leg, which had been persistent for 5 days.

RESULTS

The venous duplex ultrasound found two recent deep-vein thrombi in this leg while the D-Dimer level was lower than 220 UI/ml at admission.

CONCLUSION

This case illustrates the importance of prudent interpretation of the serum D-Dimer level.

Influence of age on the cost-effectiveness of diagnostic strategies for suspected pulmonary embolism

BACKGROUND

Age has a marked effect on the diagnostic yield of D-dimer measurement and lower limb compression ultrasonography (CUS) in patients with suspected pulmonary embolism (PE), suggesting that specific diagnostic strategies may be needed in elderly patients.

OBJECTIVE

To evaluate the cost-effectiveness of including D-dimer and CUS in the workup of PE, with particular attention to patient age.

SUBJECTS AND METHODS

We analyzed data from two recent outcome studies that enrolled 1721 consecutive outpatients with suspected PE. Both studies used a sequential diagnostic strategy that included assessment of clinical probability, D-dimer measurement, CUS, and helical computed tomography (hCT). A decision analysis model was created for analyzing cost-effectiveness according to six classes of age. The main outcome measures were 3-month quality-adjusted expected survival and costs per patient managed.

RESULTS

All strategies were equally safe, with variations in the 3-month survival never exceeding 0.5% as compared to the most effective strategy. D-dimer measurement was highly cost-saving under the age of 80 years. Above 80 years, the cost-sparing effect of D-dimer was diminished, but not completely abolished. Inclusion of CUS increased the costs of diagnostic strategies irrespective of age. Results were unchanged over a wide range of the variables of interest (costs, sensitivity, and specificity of the tests).

CONCLUSIONS

Diagnostic strategies using D-dimer are less expensive. The cost-sparing effect of D-dimer is reduced but not abolished above 80 years, suggesting that adapting specific diagnostic strategies in elderly outpatients is not mandatory. CUS is costly, and only marginally improves the safety of diagnostic strategies for PE.

Plasma markers of activated hemostasis in the early diagnosis of acute coronary syndromes

BACKGROUND

Because acute coronary syndromes (ACS) are caused by intracoronary thrombosis, plasma markers of coagulation have relevance for early diagnosis.

AIMS AND OBJECTIVES

To provide a critical review of these studies and specific attempts to close the diagnostic time gap left by traditional plasma markers of heart injury.

METHODS

Studies of ACS patients, with at least one control group, were included when blood samples were taken within 24 h after first symptoms prior to medication or intervention. Special attention was paid to studies reporting diagnostic performance, or combination of several markers into a single diagnostic index.

RESULTS

Markers with short plasma half-life (FPA, TAT, etc.) reflect ongoing thrombosis and may identify patients at increased risk. Markers with longer half-life (F1+2, D-Dimer, etc.) may be more useful to indicate a single acute thrombotic event. However, results are highly variable and depend on sampling time, clot property, degree of coronary obstruction and physiological condition. Early diagnostic performance of hemostatic markers was poor even when combined with heart injury markers.

CONCLUSIONS

Early measurement of hemostatic plasma markers in ACS patients provides pathophysiological information and may be helpful in risk stratification or to monitor anticoagulant therapy, but does not seem useful in routine clinical diagnosis of ACS.

Sensitive and quantitative, 10-min immunofluorometric assay for D-Dimer in whole blood

INTRODUCTION

Normal concentrations of D-Dimer can be used to exclude venous thromboembolism (VTE). However, methods for sensitive and quantitative D-Dimer measurements at the point-of-care (POC) are still limited.

MATERIALS AND METHODS

We developed a 10-min, non-competitive immunofluorometric assay for D-Dimer in citrated whole blood and plasma using pre-dispensed reagents dried in single assay wells. The simple, automated assay procedure comprises a 1:50 sample dilution, one-step incubation, washing, and time-resolved fluorometric measurement directly from the wet well surface.

RESULTS

The limits of detection (background + 3SD) and quantification (CV <15%) were 0.05 and 0.2 mg/L D-Dimer, respectively, and the assay was linear up to 400 mg/L. Correlations to Roche TinaQuant (r=0.726, n=200) and Biopool Auto.Dimer (r=0.190, n=149) were carried out using citrated plasma. Diagnostic sensitivity, specificity, and negative (NPV) and positive (PPV) predictive values were 98.7%, 64.4%, 99.1% and 55.1%, and 92.2%, 81.0%, 95.9% and 68.3%, respectively, using cut-off values of 0.6 and 1.0 mg/L, respectively, in outpatients with deep vein thrombosis (DVT) and/or pulmonary embolism (PE) (n=77) compared with outpatients with various other diseases (n=174). The within- and between-run CVs near the cut-off values were < or =10% in both whole blood and plasma. The 95th percentile upper range in apparently healthy individuals was 0.68 mg/L of whole blood (n=101).

CONCLUSIONS

The high sensitivity and NPV suggest that the rapid immunofluorometric assay could be valuable for rapid exclusion of VTE in outpatients. With appropriate cut-offs, the assay could potentially be used as a stand-alone test or combined with clinical probability assessment, but further studies are required.

Disseminated intravascular coagulation in pediatric patients: clinical and laboratory features and prognostic factors influencing the survival

Although disseminated intravascular coagulation (DIC) has been a well-known disorder for many years, there is lack of sufficient number of clinical trials about incidence, frequency of underlying disorders, and prognosis of DIC in children. The aim of this study was to evaluate the frequency, etiologic factors, and clinical and laboratory findings of DIC and to determine the prognostic factors influencing the mortality in hospitalized pediatric patients. Medical records of 5535 children who were hospitalized were investigated. Sixty-two patients who were diagnosed as acute DIC were enrolled. The frequency of DIC was 1.12%. The underlying etiologic factors were infection in 59 patients (95.2%) and major trauma in 3 patients (4.8%). The frequency of bleeding and thrombosis was 48.8 and 4.8%. Respiratory, cardiovascular, hepatic, renal, neurologic, and gastrointestinal dysfunction was present in 71, 67.7, 35.5, 16.1, 16.1 and 11.3% of patients, respectively. Respiratory and cardiovascular dysfunctions were significantly associated with mortality. Multiorgan dysfunction syndrome (MODS) was present in 85.5% of the patients, and 54.8% of the patients had developed acute respiratory distress syndrome (ARDS). Mortality rate was significantly high in patients with MODS and ARDS. In multivariete logistic regression analysis, only ARDS and cardiovascular dysfunction had predictive and prognostic value on mortality. None of the diagnostic laboratory tests had predictive or prognostic value and the degree of abnormality of these tests did not show any correlation with mortality. In conclusion, DIC is not a rare disorder in hospitalized children, especially in patients with sepsis, and MODS, ARDS, and respiratory and cardiovascular system dysfunctions are poor prognostic factors.

Back to the future: testing in disseminated intravascular coagulation

Following on from the first clinical observations on disseminated intravascular coagulation (DIC) in the nineteenth century, the dawn of laboratory testing for DIC began with the availability of assays that characterized the extrinsic and intrinsic pathways of coagulation. Markedly increased clotting times were the hallmark of DIC. As the understanding of the biochemistry of haemostasis and thrombosis improved, new tests were developed based on the molecular players that participate in the process. However, many are non-specific for DIC and/or are unwieldy in performance to keep apace with the demands of the acute clinical setting. The renewed emphasis in DIC for the modern laboratory of the twenty-first century has seen a return to the simple, rapid and practical global tests of coagulation within scoring systems that also capture the pathophysiological continuum by trend analysis. Additionally, new technologies based on these simple tests of coagulation hold promise in also indicating the in vivo interplay between coagulation and inflammation during DIC.

[D-dimer screening in surgical long-term intensive care patients]

BACKGROUND

Clinically unrecognized thrombosis with the danger of a pulmonary embolism represents an underestimated problem in surgical ICU patients. In patients undergoing total hip replacement for instance, over 30% develop a clinically inapparent form of thrombosis, despite initial thrombosis prophylaxis. We tried to recognize clinically inapparent thrombosis in long-term intensive care patients using D-dimer screening and ultrasound imaging.

METHODS

All surgical long-term ICU patients received intravenous heparin 5-10 IU/kg body weight and a D-dimer was assay was carried out every 2 days. If the D-dimer level surpassed 2 mg/l, ultrasound imaging of the veins in the legs, pelvis, arms and neck was performed.

RESULTS

Included in the study were 50 patients and D-dimer levels above 2 mg/l were detected in 38%. A thrombosis was proven in 63% of the patients with D-dimer values above 2 mg/l and 50% of the thrombosis were detected in the arm and neck veins very often associated with intravenous catheters.

CONCLUSION

Routine D-dimer screening and specific use of ultrasound imaging appears to be a valuable method to verify clinically inapparent thromboses in surgical ICU patients.

Screening for pulmonary embolism with a D-dimer assay: do we still need to assess clinical probability as well?

Clinical risk stratification and D-dimer assay can be of use in excluding pulmonary embolism in patients presenting to emergency departments but many D-dimer assays exist and their accuracy varies. We used clinical risk stratification combined with a quantitative latex-agglutination D-dimer assay to screen patients before arranging further imaging if required. Retrospective analysis of a sequential series of 376 patients revealed that no patient with a D-dimer of <275 ng/mL was diagnosed with pulmonary embolism, irrespective of clinical probability. We conclude that a latex-agglutination assay could be used to exclude pulmonary embolism without the necessity for clinical risk stratification. If these findings are borne out by further work, D-dimer strategies to exclude pulmonary embolism could substantially reduce imaging workload.

The predictive characteristics of D-dimer testing in outpatients with suspected venous thromboembolism: a Bayesian approach

BACKGROUND

Despite the widespread use of quantitative methods to measure D-dimer, clinical decisions commonly are based only on binary test information (positive/negative). This study aimed to determine the significance of quantitative D-dimer results in the evaluation of venous thromboembolism (VTE) by means of a differentiated Bayesian approach.

METHODS

Prospective study in 118 outpatients referred for workup of suspected pulmonary embolism (n = 75) or deep vein thrombosis (n = 43). The sensitivity and specificity of D-dimer results obtained by DD VIDAS (Biomerieux, France), STA Liatest (Diagnostica Stago, France), and D-dimer plus (Dade, US) were assessed for five different cut-offs. Further, predictive values and multilevel likelihood ratios were calculated in order to assess the operative test characteristics in excluding or confirming VTE.

RESULTS

At a cut-off of 500 ng/ml and pretest probabilities < 47%, the VIDAS provides a negative predictive value (NPV) > 95%, whereas a positive predictive value (PPV) > 95% is obtained in patients with a D-dimer > 10,000 ng/ml and pretest probabilities > 50%. At a cut-off of 500 ng/ml and pretest probabilities < 33%, the Liatest exhibits a NPV > 95%, whereas a PPV > 95% is obtained in patients with a D-dimer >10,000 ng/ml and pretest probabilities > 37%. Finally, with the D-dimer plus, a NPV > 95% is seen at a cut-off of 150 ng/ml and pretest probabilities < 30%, whereas a PPV > 95% is obtained at a cut-off > 1000 ng/ml and pretest probabilities > 67%.

CONCLUSIONS

D-dimer measurements in outpatients cannot only allow for exclusion but, in some situations, also for confirmation of venous thromboembolism. It is therefore advisable to conduct a quantitative interpretation of D-dimer results.

D-dimer testing for deep venous thrombosis: a metaanalysis

BACKGROUND

The use of D-dimer assays as a rule-out test for deep venous thrombosis (DVT) is controversial. To clarify this issue we performed a systematic review of the relevant literature.

METHODS

We identified eligible studies, using MEDLINE entries from February 1995 through October 2003, supplemented by a review of bibliographies of relevant articles. Studies reporting accuracy evaluations comparing D-dimer test results with lower extremity ultrasound or venography in symptomatic patients with suspected acute DVT were selected for review. Two reviewers critically appraised each study independently according to previously established methodologic standards for diagnostic test research. Those studies judged to be of highest quality were designated Level 1.

RESULTS

The 23 Level 1 studies reported data on 21 different D-dimer assays. There was wide variation in assay sensitivity, specificity, and negative predictive values, and major differences in methodology of reviewed studies. A multivariate analysis of assay performance, controlling for sample size, DVT prevalence, reference standard, and patient mix, found few differences among the assays in effect on test performance as measured by diagnostic odds ratio. Increasing prevalence of DVT was associated with poorer test performance (P = 0.01), whereas the choice of venography as the reference standard was associated with better test performance (P <0.005).

CONCLUSIONS

Explanations for the wide variation in assay performance include differences in biochemical and technical characteristics of the assays, heterogeneity and small size of patient groups, and bias introduced by choice of reference standards. Assay sensitivity and negative predictive value were frequently <90%, uncharacteristic of a good rule-out test. General use of D-dimer assays as a stand-alone test for the diagnosis of DVT is not supported by the literature.

[Additional utility of the ventilation scintigraphy and chest X-ray in the diagnosis of pulmonary thromboembolism]

AIM

To evaluate the utility of ventilation scintigraphy and chest X-ray in the assessment of the lung perfusion scintigraphy and to evaluate the utility of clinical findings in the diagnosis of pulmonary thromboembolism.

MATERIAL AND METHODS

A total of 100 patients who underwent a ventilation-perfusion scintigraphy due to suspicion of pulmonary thromboembolism were studied retrospectively. Three observers evaluated scintigraphic findings, blind to the other data on the patient. They consecutively added ventilation scintigraphy and chest X-ray to the perfusion study, making a consensus interpretation. Clinical findings were also evaluated. Sensitivity, specificity, positive and negative predictive values and global value test were calculated, using the final diagnosis presented by the patients on discharge as the gold standard. The Kappa statistics index was used to evaluate the degree of agreement between the three observers and the correlation between clinical and scintigraphic findings.

RESULTS

On adding the information of the ventilation to the perfusion study, specificity increased and sensitivity decreased. Kappa statistics between observers also increased. The chest X-ray did not significantly change the scintigraphic results. Little correlation was found between the clinical and scintigraphic findings, this association being greater in low probability studies.

CONCLUSIONS

We think that the performance of the ventilation study has great value in the interpretation of perfusion studies. The chest X-rays did not significantly change the scintigraphic results. Clinical data are important to establish pre-test probability and in their integration with the scintigraphy information.

False-positive D-dimer result in a patient with Castleman disease

In suspected cases of disseminated intravascular coagulation, concurrent elevation of both fibrin(ogen) degradation products (FDPs) and D-dimer levels aids in confirming the diagnosis. This pattern of results reflects the action of plasmin proteolysis of cross-linked fibrin polymers as well as fibrinogen. We report the case of a patient with human immunodeficiency virus (HIV) and Castleman disease who presented with a high-positive D-dimer level and a negative FDP level in the course of a workup for disseminated intravascular coagulation. This finding suggested the possibility of either a false-positive D-dimer or a false-negative FDP level. To investigate the former, a Western blot was performed on the patient's serum to determine the presence of the D-dimer. No D-dimer band was visualized on the Western blot, confirming the false-positive nature of the D-dimer result. Insufficient quantity of patient serum, however, prevented further investigation into the etiology of this result. The false-positive D-dimer result is likely attributable to interference caused by the patient's Castleman disease-associated monoclonal gammopathy, a phenomenon that has been reported in other immunoassays. As the development of lymphoproliferative disorders is especially common within the HIV population, and hypergammaglobulinemia in Castleman disease is particularly common, clinicians should be aware of this phenomenon when the laboratory findings do not fit the clinical picture. Although it is rare, recognition of potential paraprotein interference in immunoassays will help avoid undertreatment or overtreatment of patients based on erroneous laboratory results.

Comparison of six D-dimer methods in patients suspected of deep vein thrombosis

We evaluated six D-dimer methods to determine their sensitivity, specificity, and negative predictive values (NPV) in symptomatic patients suspected of deep vein thrombosis (DVT). In patients suspected of DVT a whole blood D-dimer test (SimpliRED, Agen) was performed, and then tested using enzyme-linked immunosorbent assay (VIDAS D-Dimer, BioMerieux; Asserachrome D-Di, Stago International; Dimertest Gold, Agen) and automated immunoturbidometric methods (Advanced D-Dimer, Dade Behring; MiniQuant, Biopool). Each D-dimer method was independently compared with radiographic results to determine sensitivity and NPV. There were 151 patients enrolled in the study. Thirty-five (23.2%) patients had a positive Doppler ultrasound, with 26 proximal, eight distal, and one patient with both proximal and distal thrombus. Two patients (1.3%) had inconclusive studies and were excluded from the analyses. For all patients, the sensitivities for the rapid D-dimer methods were: SimpliRED, 82.3% [95% confidence interval (CI), 80.3-84.3%]; VIDAS D-Dimer, 91.4% (95% CI, 89.9-92.9%); MiniQuant D-Dimer, 96.3% (95% CI, 95.1-97.5%); and Advanced D-Dimer, 97.1% (95% CI, 96.3-97.9%). The sensitivity improved for SimpliRED (86.4%; 95% CI, 83.3-89.4%), VIDAS D-Dimer (95.5%; 95% CI, 85.0-100%), MiniQuant D-Dimer (100%; 95% CI, 96.9-100%) and Advanced D-Dimer (100%; 95% CI, 98.9-100%) in the inpatient population. The automated immunoturbidometric methods, the MiniQuant D-Dimer and Advanced D-Dimer, demonstrated comparable sensitivities and NPV with the VIDAS D-Dimer method in symptomatic patients suspected of DVT, which would suggest that these newer D-dimer methods could be used as part of the diagnostic algorithm for patients suspected of DVT.

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

Waveform analysis of clotting test optical profiles in the diagnosis and management of disseminated intravascular coagulation (DIC)

Transmittance waveform charts the changes in light transmittance on standard coagulation assays, such as the prothrombin time (PT) and activated partial thromboplastin time (APTT). Analysis and characterization of these data on photo-optical coagulation analysers provides additional qualitative and quantitative information to that obtained using the clotting time alone. The most thoroughly evaluated clinical application is that of the biphasic APTT waveform with disseminated intravascular coagulation (DIC). The degree of waveform abnormality correlates directly with the severity of haemostatic dysfunction and allows for both the prediction and monitoring from non-overt to overt DIC. As its performance is simple and rapid, this provides the means for targeting therapeutic intervention to an earlier stage of DIC. The recent identification that the mechanism underlying the biphasic waveform is a complex that exists in vivo between C reactive protein with very low density lipoprotein, provides potentially important insights into the molecular pathogenesis of DIC. Thus, in addition to the immediate clinical utility in diagnostic practice, it has important applications as a research tool. Preliminary experience in the application of this technology to the diagnosis and management of the haemophilias and the lupus anticoagulant syndrome has also provided evidence of the power and utility of waveform analysis in essentially simple clotting assays.