Advances in D-dimer testing: progress in harmonization of clinical assays and innovative detection methods

The D-dimer is a sensitive indicator of coagulation and fibrinolysis activation, especially valuable as a biomarker of intravascular thrombosis. Measurement of plasma D-dimer levels plays a crucial role in the diagnosis and monitoring of conditions such as deep vein thrombosis, pulmonary embolism, and disseminated intravascular coagulation. A variety of immunoassays, including enzyme-linked immunosorbent assays, latex-enhanced immunoturbidimetric assays, whole-blood aggregation analysis, and immunochromatography assays, are widely used in clinical settings to determine D-dimer levels. However, the results obtained from different D-dimer assays vary significantly. These assays exhibit intra-method coefficients of variation ranging from 6.4% to 17.7%, and the measurement discrepancies among different assays can be as high as 20-fold. The accuracy and reliability of D-dimer testing cannot be guaranteed due to the lack of an internationally endorsed reference measurement system (including reference materials and reference measurement procedures), which may lead to misdiagnosis and underdiagnosis, limiting its full clinical application. In this review, we present an in-depth analysis of clinical D-dimer testing, summarizing the existing challenges, the current state of metrology, and progress towards harmonization. We also review the latest advancements in D-dimer detection techniques, which include mass spectrometry and electrochemical and optical immunoassays. By comparing the basic principles, the definition of the measurand, and analytical performance of these methods, we provide an outlook on the potential improvements in D-dimer clinical testing.

D-dimer Testing in Pulmonary Embolism with a Focus on Potential Pitfalls: A Narrative Review

D-dimer is a multifaceted biomarker of concomitant activation of coagulation and fibrinolysis, which is routinely used for ruling out pulmonary embolism (PE) and/or deep vein thrombosis (DVT) combined with a clinical pretest probability assessment. The intended use of the tests depends largely on the assay used, and local guidance should be applied. D-dimer testing may suffer from diagnostic errors occurring throughout the pre-analytical, analytical, and post-analytical phases of the testing process. This review aims to provide an overview of D-dimer testing and its value in diagnosing PE and discusses the variables that may impact the quality of its laboratory assessment.

Longitudinal association between cognitive depressive symptoms and D-dimer levels in patients following acute myocardial infarction

BACKGROUND

A prothrombotic tendency could partially explain the poor prognosis of patients with coronary heart disease and depression. We hypothesized that cognitive depressive symptoms are positively associated with the coagulation activation marker D-dimer throughout the first year after myocardial infarction (MI).

METHODS

Patients with acute MI (mean age 60 years, 85% men) were investigated at hospital admission (n = 190), 3 months (n = 154) and 12 months (n = 106). Random linear mixed regression models were used to evaluate the relation between cognitive depressive symptoms, assessed with the Beck depression inventory (BDI), and changes in plasma D-dimer levels. Demographics, cardiac disease severity, medical comorbidity, depression history, medication, health behaviors, and stress hormones were considered for analyses.

RESULTS

The prevalence of clinical depressive symptoms (13-item BDI score ≥ 6) was 13.2% at admission and stable across time. Both continuous (p < .05) and categorical (p < .010) cognitive depressive symptoms were related to higher D-dimer levels over time, independent of covariates. Indicating clinical relevance, D-dimer was 73 ng/ml higher in patients with a BDI score ≥ 6 versus those with a score < 6. There was a cognitive depressive symptom-by-cortisol interaction (p < .05) with a positive association between cognitive depressive symptoms and D-dimer when cortisol levels were high (p < .010), but not when cortisol levels were low (p > .05). Fluctuations (up and down) of cognitive depressive symptoms and D-dimer from one investigation to the next showed also significant associations (p < .05).

CONCLUSIONS

Cognitive depressive symptoms were independently associated with hypercoagulability in patients up to 1 year after MI. Hypothalamic-pituitary-adrenal axis could potentially modify this effect.

Women in sports: the applicability of common national reference intervals for inflammatory and coagulation biomarkers (HemSter Study)

Introduction

Intensive physical activity causes functional and metabolic changes in the athlete’s organism. The study aimed to verify the common national available reference intervals (RIs) for common inflammatory and screening coagulation tests in a population of healthy young female athletes.

Materials and methods

One hundred and twenty-one female athletes (age range: 16–34), from various sports disciplines (water polo, handball, volleyball, football, basketball), were included in the study. All participants completed the international physical activity short-form questionnaire. Blood samples were collected between 8–10 am, after an overnight fast, before any physical activity. Reference intervals were determined according to Clinical & Laboratory Standards Institute EP28-A3C Guidelines.

Results

Calculated RIs for white blood cell count (WBC), prothrombin time (PT), and activated partial thromboplastin time (APTT) ratio were in accordance with the common national RIs. Calculated RI for C-reactive protein (CRP) was lower (< 2.9 mg/L) than the proposed cut-off for a healthy population (< 5.0 mg/L). Reference interval for fibrinogen was higher (1.9–4.4 g/L), than the available RIs (1.8–3.5 g/L). D-dimer cut-off value was set at 852 µg/L fibrinogen equivalent units (FEU), higher than the proposed 500 µg/L FEU for venous thromboembolism (VTE) exclusion.

Conclusions

The applicability of the available RIs for WBC count, PT, and APTT-ratio was confirmed. However, RIs for CRP and fibrinogen differed significantly than the available common national RIs for the healthy non-athletes’ population. A higher cut-off for D-dimers should be extensively verified before implementation for VTE diagnosis exclusion in a group of healthy young female athletes.

Verification of automated latex-enhanced particle immunoturbidimetric D-Dimer assays on different analytical platforms and comparability of test results

INTRODUCTION

The aim of the study was the analytical verification of automated latex-enhanced particle immunoturbidimetric (LPIA) D-Dimer assay INNOVANCE D-dimer on Sysmex CS-5100 and Atellica COAG 360 analysers, and HemosIL D-dimer HS500 on ACL TOP 550, as well as the comparison with the enzyme-linked immunofluorescent assay (ELFA) on the miniVidas analyser.

MATERIALS AND METHODS

Verification included assessment of within-run and between-run precision, bias, measurement uncertainty (MU), verification of the cut-off, method comparison between all assessed assays, and the reference commercial ELFA VIDAS D-Dimer Exclusion II.

RESULTS

Within-run coefficients of variations (CVs) ranged from 1.6% (Atellica COAG 360) to 7.9% (ACL TOP 550), while between-run CVs ranged from 1.7% (Sysmex CS-5100) to 6.9% (Atellica COAG 360). Spearman's rank correlation coefficients were > 0.99 between LPIAs and ≥ 0.93 when comparing ELFA with LPIA. Passing-Bablok regression analysis yielded constant and proportional difference for comparison of ACL TOP 550 with both Sysmex CS-5100 and Atellica COAG360, and for miniVidas with Atellica COAG360. Small proportional difference was found between miniVidas and both Sysmex CS-5100 and ACL TOP 550. Calculated MUs using D-dimer HS 500 calibrator were 12.6% (Sysmex CS-5100) and 15.6% (Atellica COAG 360), while with INNOVANCE D-dimer calibrator 12.0% (Sysmex CS-5100), 10.0% (Atellica COAG 360) and 28.1% (ACL TOP 550). Excellent agreement of results was obtained, with occasional discrepancies near the cut-off. The cut-off (0.5 mg/L FEU) was confirmed.

CONCLUSIONS

The obtained results prove satisfactory analytical performance of LPIAs, their high comparability and almost equal discriminatory characteristics, suggesting them as a valid alternative to ELFA.

D-dimer can help differentiate suspected pulmonary embolism patients that require anti-coagulation

Objectives

Determine whether D-dimer concentration in the absence of imaging can differentiate patients that require anti-coagulation from patients who do not require anti-coagulation.

Methods

Data was obtained retrospectively from 366 hemodynamically stable adult ED patients with suspected pulmonary embolism (PE).

Patients were categorized by largest occluded artery and aggregated into: ‘Require anti-coagulation’ (main, lobar, and segmental PE), ‘Does not require anti-coagulation’ (sub-segmental and No PE), ‘High risk of deterioration’ (main and lobar PE), and ‘Not high risk of deterioration’ (segmental, sub-segmental, and No PE) groups.

Wilcoxon rank-sum test was used for 2 sample comparisons of median D-dimer concentrations. Receiver operating characteristic (ROC) curve analysis was utilized to determine a D-dimer cut-off that could differentiate ‘Require anti-coagulation’ from ‘Does not require anti-coagulation’ and ‘High risk of deterioration’ from ‘Low risk of deterioration’ groups.

Results

The ‘Require anti-coagulation’ group had a maximum area under the curve (AUC) of 0.92 at an age-adjusted D-dimer cut-off of 1540 with a specificity of 86% (95% CI, 81–91%), and sensitivity of 84% (79–90%). The ‘High risk of deterioration’ group had a maximum AUC of 0.93 at an age-adjusted D-dimer cut-off of 2500 with a specificity of 90% (85–93%) and sensitivity of 83% (77–90%).

Conclusions

An age-adjusted D-dimer cut-off of 1540 ng/mL differentiates suspected PE patients requiring anti-coagulation from those not requiring anti-coagulation. A cut-off of 2500 differentiates those with high risk of clinical deterioration from those not at high risk of deterioration. When correlated with clinical outcomes, these cut-offs can provide an objective method for clinical decision making when imaging is unavailable.

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ED providers are faced with risks and benefits when empirically administering anti-coagulation for suspected PE patients.

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We show that D-dimer concentration can be used as a clinical decision making tool to minimize these risks.

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A D-dimer cut-off of 1540 ng/mL can be used to minimize unnecessary anti-coagulation exposure in patients who do not need it.

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Using a 2500 ng/mL D-dimer cut-off minimizes the risk of withholding treatment for those at risk of clinical deterioration.

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Both cut-offs along with clinical gestalt are an objective measure weighing the risks & benefits of empiric anti-coagulation.

Generation of a Monoclonal Antibody against D-Dimer Using HTS-Based LiCA

D-dimer is an essential diagnostic index of thrombotic diseases. Since the existing anti-D-dimer antibodies vary in quality and specificity, a search for alternative anti-D-dimer antibodies is required. The present study aimed to screen a novel monoclonal antibody (mAb) against D-dimer using a light-initiated chemiluminescence assay (LiCA). In this work, mice were immunized with antigen prepared from human plasma by enzyme hydrolysis. After screening, a novel mAb, DD 2G11, was obtained. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis indicated that DD 2G11 could be used as a standard marker for D-dimer. The isotype of DD 2G11 was IgG1, the K_a value was 0.646 nM-1, and the K_d value was 50 nM, indicating that the binding affinity to D-dimer was very high. Furthermore, no cross-reactivity between DD 2G11 and other fibrinogen degradation products (FgDPs) was found. Finally, the correlation between DD 2G11 and the reference antibody (commercial antibody) was investigated by analyzing 56 clinical samples using a latex-enhanced turbidimetric immunoassay (LTIA). The R² value of the linear regression was 0.94538, indicating that DD 2G11 met clinical requirements. In conclusion, the present study provides a more expeditious protocol to screen mAbs and provides a clinically usable mAb against D-dimer.

D-dimer: Preanalytical, analytical, postanalytical variables, and clinical applications

D-dimer is a soluble fibrin degradation product deriving from the plasmin-mediated degradation of cross-linked fibrin. D-dimer can hence be considered a biomarker of activation of coagulation and fibrinolysis, and it is routinely used for ruling out venous thromboembolism (VTE). D-dimer is increasingly used to assess the risk of VTE recurrence and to help define the optimal duration of anticoagulation treatment in patients with VTE, for diagnosing disseminated intravascular coagulation, and for screening medical patients at increased risk of VTE. This review is aimed at (1) revising the definition of D-dimer; (2) discussing preanalytical variables affecting the measurement of D-dimer; (3) reviewing and comparing assay performance and some postanalytical variables (e.g. different units and age-adjusted cutoffs); and (4) discussing the use of D-dimer measurement across different clinical settings.

Association of sleep problems with neuroendocrine hormones and coagulation factors in patients with acute myocardial infarction

Background

Obstructive sleep apnea (OSA) and insomnia are frequent sleep problems that are associated with poor prognosis in patients with coronary heart disease. The mechanisms linking poor sleep with an increased cardiovascular risk are incompletely understood. We examined whether a high risk of OSA as well as insomnia symptoms are associated with neuroendocrine hormones and coagulation factors in patients admitted with acute myocardial infarction.

Methods

We assessed 190 patients (mean age 60 years, 83% men) in terms of OSA risk (STOP screening tool for the assessment of high vs. low OSA risk) and severity of insomnia symptoms (Jenkins Sleep Scale for the assessment of subjective sleep difficulties) within 48 h of an acute coronary intervention. Circulating concentrations of epinephrine, norepinephrine, cortisol, fibrinogen, D-dimer, and von Willebrand factor were measured the next morning. The association of OSA risk and insomnia symptoms with neuroendocrine hormones and coagulation factors was computed using multivariate models adjusting for demographic factors, health behaviors, somatic and psychiatric comorbidities, cardiac disease-related variables, and OSA risk in the model for insomnia symptoms, respectively, for insomnia symptoms in the model for OSA risk.

Results

High OSA risk was identified in 41% of patients and clinically relevant insomnia symptoms were reported by 27% of patients. Compared to those with low OSA risk, patients with high OSA risk had lower levels of epinephrine (p = 0.015), norepinephrine (p = 0.049) and cortisol (p = 0.001). More severe insomnia symptoms were associated with higher levels of fibrinogen (p = 0.037), driven by difficulties initiating sleep, and with lower levels of norepinephrine (p = 0.024), driven by difficulties maintaining sleep.

Conclusions

In patients with acute myocardial infarction, sleep problems are associated with neuroendocrine hormones and coagulation activity. The pattern of these relationships is not uniform for patients with a high risk of OSA and those with insomnia symptoms, and whether they contribute to adverse cardiovascular outcomes needs to be established.

Trial registration

ClinicalTrials.gov NCT01781247.

Comorbidity burden conditions the prognostic performance of D-dimer in elderly patients with acute pulmonary embolism

INTRODUCTION

The prognostic accuracy of D-dimer for risk assessment in acute Pulmonary Embolism (APE) patients may be hampered by comorbidities. We investigated the impact of comorbidity burden (CB) by using the Charlson Comorbidity Index (CCI), on the prognostic ability of D-dimer to predict 30 and 90-day mortality in hemodynamically stable elderly patients with APE.

METHODS

All patients aged >65 years with normotensive APE, consecutively evaluated in the Emergency Department since 2010 through 2014 were included in this retrospective cohort study. Area under the curve (AUC) and ½ Net Reclassification Improvement (NRI) were calculated.

RESULTS

Study population: 162 patients, median age: 79.2 years. The optimal cut-off value of CCI score for predicting mortality was ≤1 (Low CB) and >1 (High CB), AUC = 0.786. Higher levels of D-dimer were associated with an increased risk death at 30 (HR = 1.039, 95%CI:1.000-1.080, p = 0.049) and 90 days (HR = 1.039, 95%CI:1.009-1.070, p = 0.012). When added to simplified Pulmonary Embolism Severity Index (sPESI) score, D-dimer increased significantly the AUC for predicting 30-day mortality in Low CB (AUC = 0.778, 95%CI:0.620-0.937, ½NRI = 0.535, p = 0.015), but not in High CB patients (AUC = 0.634, 95%CI:0.460-0.807, ½ NRI = 0.248, p = 0.294). Similarly, for 90-day mortality D-dimer increased significantly the AUC in Low CB (AUC = 0.786, 95%CI:0.643-0.929, ½NRI = 0.424, p-value = 0.025), but not in High CB patients (AUC = 0.659, 95%CI:0.541-0.778, ½NRI = 0.354, p-value = 0.165).

CONCLUSION

In elderly patients with normotensive APE, comorbidities condition the prognostic performance of D-dimer, which was found to be a better predictor of death in subjects with low CB. These results support multimarker strategies for risk assessment in this population.

Troponin I and D-Dimer for Discriminating Acute Pulmonary Thromboembolism from Myocardial Infarction

BACKGROUND

Acute pulmonary thromboembolism (APTE) is a life-threatening condition, often manifesting with chest pain, dyspnea, and increased cardiac biomarkers including cardiac troponin I (CTI) and D-dimer. Therefore, APTE is often misdiagnosed with classical non-ST elevation myocardial infarction (NSTEMI), resulting in unnecessary coronary interventions and a delay of therapy.

OBJECTIVES

Our aim was to distinguish APTE from NSTEMI based on CTI and D-dimer levels.

METHODS

Complete clinical and laboratory data sets from APTE patients (n = 123) were compared with matched NSTEMI patients (n = 123) who presented with chest pain. The APTE diagnosis was confirmed by chest tomography, angiography, or radionuclide ventilation-perfusion scan, while NSTEMI was established by clinical symptoms, cardiac biomarkers, and coronary angiography. Clinical characteristics, CTI (initial and peak), and D-dimer levels at presentation were retrospectively analyzed.

RESULTS

The clinical characteristics were not different between APTE and NSTEMI patients. However, significantly lower initial CTI (0.2 ± 0.5 vs. 4.4 ± 9.5 ng/ml) and peak CTI (0.7 ± 2.7 vs. 17.1 ± 20.4 ng/ml), but higher initial D-dimer (9.8 ± 9.4 vs. 1.6 ± 3.6 ng/ml), distinguished APTE from NSTEMI. By receiver operating characteristic curve analysis, the cutoff values for initial CTI, peak CTI, and D-dimer were 0.25, 0.98, and 3.18 ng/ml, respectively.

CONCLUSION

Patients with APTE exhibited lower initial and peak CTI but higher D-dimer levels than NSTEMI patients. Assessing cardiac biomarkers is useful for differentiating APTE from NSTEMI. Further large randomized biomarker studies are urgently needed to facilitate a better APTE diagnosis since clinical characteristics are not particularly helpful.

Widely Used Types and Clinical Applications of D-Dimer Assay

D-dimers are formed by the breakdown of fibrinogen and fibrin during fibrinolysis. D-dimer analysis is critical for the diagnosis of deep vein thrombosis, pulmonary embolism, and disseminated intravascular coagulation. Modern assays for D-dimer are monoclonal antibody based. The enzyme-linked immunosorbent assay (ELISA) is the reference method for D-dimer analysis in the central clinical laboratory, but is time consuming to perform. Recently, a number of rapid, point-of-care D-dimer assays have been developed for acute care settings that utilize a variety of methodologies. In view of the diversity of D-dimer assays used in central laboratory and point-of-care settings, several caveats must be taken to assure the proper interpretation and clinical application of the results. These include consideration of preanalytical variables and interfering substances, as well as patient drug therapy and underlying disease. D-dimer assays should also be validated in clinical studies, have established cut-off values, and reported according to the reagent manufacturers recommendations.

Timing and duration of compression therapy after deep vein thrombosis

After deep vein thrombosis (DVT) 20-50%, of patients develop post thrombotic syndrome (PTS). Up till now, there is no effective treatment for PTS and prevention is therefore of major importance. Compression therapy after DVT, with elastic compression stockings (ECS), is the only available preventive measure for PTS. However, the usefulness, timing, and duration of compression therapy are matters of debate. The effect of early compression on the long-term development of PTS is still unclear as studies performed so far have conflicting outcomes.16–19 The effectiveness of ECS therapy initiated in the sub-acute phase was assessed in three large randomized controlled trials. Kahn et al could not reproduce the large risk reduction found in the trials by Brandjes and Prandoni et al.20–22 Also for the optimal duration of ECS therapy, a certain conclusion has yet to be drawn. Therefore identification of patients who most likely will benefit from ECS therapy as well as the optimal ECS treatment strategy remain subjects for further study.

Evaluating the Use of a Negative D-Dimer and Modified Low Wells Score in Excluding above Knee Deep Venous Thrombosis in an Outpatient Population, Assessing Need for Diagnostic Ultrasound

Aims. Colour doppler ultrasonography (CDUS) is widely used in the diagnosis of deep venous thrombosis (DVT); however, the number of scans positive for above knee DVT is low. The present study evaluates the reliability of the D-dimer test combined with a clinical probability score (Wells score) in ruling out an above knee DVT and identifying patients who do not need a CDUS. Materials and Method. This study is a retrospective audit and reaudit of a total of 816 outpatients presenting with suspected lower limb DVT from March 2009 to March 2010 and from September 2011 to February 2012. Following the initial audit, a revised clinical diagnostic pathway was implemented. Results. In our initial audit, seven patients (4.9%) with a negative D-dimer and a low Wells score had a DVT. On review, all seven had a risk factor identified that was not included in the Wells score. No patient with negative D-dimer and low Wells score with no extra clinical risk factor had a DVT on CDUS (negative predictive value 100%). A reaudit confirmed adherence to our revised clinical diagnostic pathway. Conclusions. A negative D-dimer together with a low Wells score and no risk factors effectively excludes a lower limb DVT and an ultrasound is unnecessary in these patients.

A higher d-dimer threshold safely rules-out pulmonary embolism in very elderly emergency department patients

INTRODUCTION

D-dimer is commonly used in the workup of suspected Pulmonary Embolism (PE), but its specificity decreases with age. We evaluated whether using a higher cutoff value for D-dimer could increase the test specificity without reducing its sensitivity for ruling-out PE in elderly and very elderly patients presenting to the Emergency Department (ED).

MATERIAL AND METHODS

All patients with D-dimer and pulmonary Computed Tomography Angiography (CTA) performed in the ED of Vimercate Hospital, from 2010 through 2012 for clinical suspicion of PE were included in this retrospective cohort study.

RESULTS

Study population 481 patients (63.4% women, mean age 73.0 ± 16.1 years, confirmed PE 22.5%). In very elderly patients (aged 80 or more years, n=191), compared with standard 490 ng/mL D-dimer threshold, both higher fixed (1000 ng/mL) and age-adjusted cutoffs increase the specificity of D-dimer for the exclusion of PE maintaining a Negative Predictive Value of 100%. Potentially avoided CTAs were 12(6.3%) using 1000 ng/mL cutoff and 10(5.2%) age-adjusted. In very elderly patients the Number Needed to Test was incalculable for the standard cutoff (0 cases), 16 for 1000 ng/mL and 19 for age-adjusted. In patients with PE, index episode mortality was 6.5%, and death occurred only in subjects with D-dimer values above 1000ng/mL and age-adjusted thresholds.

CONCLUSION

For very elderly patients with suspected PE in ED, both higher fixed D-dimer (1000 ng/mL) and age-adjusted thresholds increase test specificity for excluding PE without reducing its sensitivity, leading to a safe reduction in the number of CTAs.

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.

[Age-adjusted D-dimer cut-offs to diagnose thromboembolic events: validation in an emergency department]

BACKGROUND

In elderly patients, an unspecific increase of fibrin degradation products in blood is observed. Thus, the D-dimer test to rule out thromboembolic events has a high false-positive rate in elderly patients. Our aim was to validate an age-adjusted D-dimer cut-off and to assess its utility in elderly patients.

METHODS

In a retrospective cohort of outpatients (n = 1033) presenting to our emergency department with suspected acute pulmonary embolism and/or deep vein thrombosis (PE/DVT), age-adjusted D-dimer cut-off values were derived using receiver operating characteristic (ROC) curve analysis. Subsequently, the proportion of patients with normal D-dimer and false-negative test results, respectively, and the number needed-to-test (NNT) were compared for conventional and age-adjusted cut-off values.

RESULTS

Using the conventional cut-off of 0.5 mg/dl, PE/DVT could be excluded in 68 % of patients, whereas the age-adjusted cut-off [(age × 0.016) mg/l] ruled out 77 % of patients. Particularly in patients > 70 years, the negative prediction accuracy of excluding a PE/DVT increased explicitly. The failure rate of the age-adjusted cut-off value was 0.8 % (95 % confidence interval 0.3-1.6 %).

CONCLUSION

The age-adjusted D-dimer cut-off point increases the proportion of older patients, in whom an acute thromboembolic event can be excluded.

Serum D-dimer concentrations in nephrotic syndrome track with albuminuria, not estimated glomerular filtration rate

BACKGROUND

The nephrotic syndrome is associated with an increased risk of venous and arterial thrombosis. There are little published data on the distribution, interpretation or determinants of serum D-dimer levels in patients with the nephrotic syndrome. We aimed to describe this relationship.

METHODS

This was a cross-sectional study of 100 patients with the nephrotic syndrome. Multivariate linear regression was used to evaluate for independent predictors of elevated D-dimer levels. Patients were observed for a period of 2 years after the baseline measurement of D-dimer level to assess for subsequent clinically evident thrombosis.

RESULTS

On univariate linear regression, D-dimer elevation was associated with age in years β (95% CI) 0.02 (0.016, 0.03), log-transformed urinary protein:creatinine ratio in g/g 0.439 (0.32, 0.558) and inversely with serum albumin in g/l -0.05 (-0.073, -0.035) and estimated glomerular filtration rate (eGFR) in ml/min/1.73 m(2) -0.01 (-0.016, -0.003). On multivariate linear regression, age in years β (95% CI) 0.019 (0.012, 0.026), serum albumin in g/l -0.023 (-0.043, -0.003), and log-transformed urinary protein:creatinine ratio in g/g 0.266 (0.124, 0.408) were independently associated with elevated D-dimer levels.

CONCLUSION

D-dimer levels are commonly raised in the nephrotic syndrome in the absence of clinically evident thrombosis, and are independently associated with age, degree of proteinuria and serum albumin, but not with eGFR. Baseline levels of D-dimer did not predict subsequent episodes of clinically evident thrombosis after 2 years of follow-up.

Markers of coagulation, fibrinolysis and inflammation in relation to post-thrombotic syndrome

BACKGROUND

Post-thrombotic syndrome (PTS) occurs in 20-50% of patients after a deep venous thrombosis (DVT). It is difficult to accurately predict which patients will develop PTS. Biomarkers could be a valuable tool for PTS risk assessment.

OBJECTIVES

To investigate whether increased levels of factor (F)VIII, C-reactive protein (CRP) or D-dimer, over time, are associated with the development of PTS in patients after an acute DVT.

METHODS

PTS status was assessed using the Villalta scale. Blood sampling was performed at three points during follow-up.

RESULTS

A cohort of 228 consecutive patients was included after an acute DVT. At T1 (12 months after index DVT), both levels of D-dimer (median 725 ng mL(-1) [interquartile range, IQR 400-1400[ vs. 378 ng mL(-1) [251-652] P=0.004) and CRP (median 3.9 mg L(-1) [IQR 1.6-8.5] vs. 2.4 mg L(-1) [1.0-4.3] P=0.018) were increased in patients with PTS, compared with patients without PTS. Factor (F)VIII was not associated with PTS. In the multivariate logistic regression analysis, varicosities (odds ratio [OR] 13.4 95% confidence interval [CI] 3.0-59.1 P=0.001), a previous ipsilateral DVT (OR 6.3 95% CI 1.5-26.9 P=0.012) and CRP>5 mg L(-1) on T1 (OR 8.0 95% CI 2.4-26.4 P=0.001) were significantly associated with PTS.

CONCLUSIONS

Besides previous ipsilateral DVT and varicosities, CRP>5 mg L(-1) at T1 was strongly and independently associated with PTS. Persistent inflammation rather than hypercoagulability might be the most important etiological factor in PTS, and may be a target for future therapy. The development of a risk score for PTS, including both clinical risk factors and biomarker levels, such as CRP, might be desirable.