D-dimer levels and 15-day outcome in acute pulmonary embolism. Findings from the RIETE Registry

Risk stratification of acute pulmonary embolism

Risk stratification of patients with acute pulmonary embolism (PE) assists with the selection of appropriate initial therapy and treatment setting. Patients with acute symptomatic PE that present with arterial hypotension or shock have a high risk of death, and treatment guidelines recommend strong consideration of reperfusion in this setting. For haemodynamically stable patients with PE, the combination of a negative clinical prognostic score and the absence of computed tomography-assessed right ventricle enlargement may accurately identify those at low-risk of short-term complications after the diagnosis of PE, and such patients might benefit from an abbreviated hospital stay or outpatient therapy. Some evidence suggests that the accumulation of factors indicating worse outcomes from PE on standard anticoagulation identifies the more severe stable patients with acute PE who might benefit from intensive monitoring and recanalization procedures, particularly if haemodynamic deterioration occurs. Current risk classifications have several shortcomings that might adversely affect clinical and healthcare decisions. Ongoing initiatives aim to address many of those shortcomings, and will hopefully help optimize risk stratification algorithms and treatment strategies.

How artificial intelligence during the pandemic modified the role of a biomarker as d-dimer

Artificial intelligence (AI) was introduced in medicine to make some difficult decision-making regarding diagnostics and/or treatments easy. Its application derives from the improvement of information obtained with computer sciences and informatics, in particular with information derived by algorithms obtained with special informatics support as machine learning. The scenario of hospital changes induced by the COVID-19 pandemic makes easy the application of AI for some clinical updates. Being lung failure with pulmonary embolism is the most common cause of death for inpatients with COVID-19, some biomarkers such as the d-dimer are constantly used associated with other clinical features in order to improve medical assistance. For this reason, d-dimer during the pandemic changed its traditional use for predictive negative value in patients with suspected pulmonary embolism and took relevance for its values giving the chance to change the intensity of anticoagulation for several inpatients. In most cases, according to data reported from several cohorts, these changes improved the morbidity and mortality of a significant percentage of inpatients with COVID-19. The International medical prevention registry on venous thromboembolism and d-dimer and modified sepsis-induced coagulopathy scores were the most used scores derived from AI and dedicated to these clinical aspects in inpatients with COVID-19. Therefore, this review was dedicated to flexible changes that we can use after d-dimer values in different clinical scenarios that vary from disseminated intravascular coagulation to pulmonary embolism to COVID-19.

Association between D-dimer and long-term mortality in patients with acute severe hypertension visiting the emergency department

OBJECTIVE

High levels of D-dimer, a marker of thrombotic events, are associated with poor outcomes in patients with various cardiovascular diseases. However, there has been no research on its prognostic implications in acute severe hypertension. This study investigated the association between D-dimer levels and long-term mortality in patients with severe acute hypertension who visited the emergency department.

DESIGN AND METHOD

This observational study included patients with acute severe hypertension who visited the emergency department between 2016 and 2019. Acute severe hypertension was defined as a systolic blood pressure ≥ 180 mmHg or a diastolic blood pressure ≥ 100 mmHg. Among the 10,219 patients, 4,127 who underwent D-dimer assay were analyzed. The patients were categorized into tertiles based on their D-dimer levels at the time of emergency department admission.

RESULTS

Among the 4,127 patients with acute severe hypertension, 3.1% in the first (lowest) tertile, 17.0% in the second tertile, and 43.2% in the third (highest) tertile died within 3 years. After the adjustment for confounding variables, the third tertile of the D-dimer group (hazard ratio, 6.440; 95% confidence interval, 4.628-8.961) and the second tertile of the D-dimer group (hazard ratio, 2.847; 95% confidence interval, 2.037-3.978) had a significantly higher risk of all-cause mortality over 3 years than the first tertile of the D-dimer group.

CONCLUSIONS

D-dimer may be a useful marker for identifying the risk of mortality among patients with acute severe hypertension who visit the emergency department.

Relationship between baseline D-dimer and prognosis in Japanese patients with venous thromboembolism: Insights from the J'xactly study

Background

D-dimer is a biomarker of fibrin production and degradation, and changes in D-dimer concentration suggest fibrin clot formation, which is associated with thromboembolism and hypercoagulable states. Thus, an elevated D-dimer concentration could be a useful prognostic predictor for patients with venous thromboembolism (VTE).

Methods and results

In this subanalysis of the J'xactly study, a prospective multicenter study conducted in Japan, we examined the clinical outcomes of 949 patients with VTE stratified by baseline D-dimer concentration. The median D-dimer concentration was 7.6 μg/ml (low D-dimer group: <7.6 μg/ml [n = 473, 49.8%]; high D-dimer group: ≥7.6 μg/ml [n = 476, 50.2%]). The mean age of the patients was 68 years, and 386 patients (40.7%) were male. Compared with the low D-dimer group, the high D-dimer group had more frequent pulmonary embolism with or without deep vein thrombosis (DVT), proximal DVT, atrial fibrillation, or diabetes mellitus, and underwent intensive treatment with 30 mg/day rivaroxaban. The incidence of composite clinically relevant events (recurrence or exacerbation of symptomatic VTE, acute coronary syndrome [ACS], ischemic stroke, death from any cause, or major bleeding) was higher in the high D-dimer group than in the low D-dimer group (11.1% vs. 7.5% per patient-year; hazard ratio, 1.46; 95% confidence interval, 1.05-2.04; p = 0.025). There was no significant difference between the high and low D-dimer groups in the incidence of VTE (2.8% vs. 2.5% per patient-year, respectively; p = 0.788), ACS (0.4% per patient-year vs. not observed, respectively; p = 0.078), or major bleeding (4.0% vs. 2.1% per patient-year, respectively; p = 0.087), but there was a significant difference in the incidence of ischemic stroke (1.0% per patient-year vs. not observed, respectively; p = 0.004).

Conclusion

Elevated D-dimer concentration may be an important prognostic predictor in Japanese patients with VTE.Clinical Trial Registration: UMIN CTR, UMIN000025072 (https://www.umin.ac.jp/ctr/index.htm).

D-Dimer beyond Diagnosis of Pulmonary Embolism: Its Implication for Long-Term Prognosis in Cardio-Oncology Era

Venous thromboembolism (VTE) is a common comorbidity of cancer, often referred to as cancer-associated thrombosis (CAT). Even though its prevalence has been increasing, its clinical picture has not been thoroughly investigated. In this single-center retrospective observational study, 259 patients who were treated for pulmonary embolism (PE) between January 2015 and December 2020 were available for analysis. The patients were divided by the presence or absence of concomitant malignancy, and those with malignancy (N = 120, 46%) were further classified into active (N = 40, 15%) and inactive groups according to the treatment status of malignancy. In patients with malignancy, PE was more often diagnosed incidentally by computed tomography or D-dimer testing, and the proportion of massive PE was lower. Although D-dimer levels overall decreased after the initiation of anticoagulation therapy, concomitant malignancy was independently associated with higher D-dimer at discharge despite the lower severity of PE at onset. The patients with malignancy had a poor prognosis during post-discharge follow-up. Active malignancy was independently associated with major adverse cardiovascular events (MACE) and major bleeding. D-dimer at discharge was an independent predictor of mortality even after adjustment for malignancy. This study's findings suggest that CAT-PE patients might have hypercoagulable states, which can potentially lead to a poorer prognosis.

D-dimer levels at diagnosis and long-term clinical outcomes in venous thromboembolism: from the COMMAND VTE Registry

The relationship between D-dimer level at diagnosis and long-term clinical outcomes has not been fully evaluated in venous thromboembolism (VTE). The COMMAND VTE Registry is a multicenter registry enrolling consecutive acute symptomatic VTE patients in Japan. Patients with available D-dimer levels at diagnosis (N = 2852) were divided into 4 groups according to the D-dimer levels; Quartile 1 (0.0-4.9 µg/mL): N = 682, Quartile 2 (5.0-9.9 µg/mL) N = 694, Quartile 3 (10.0-19.9 µg/mL) N = 710, and Quartile 4 (≥ 20.0 µg/mL): N = 766. The cumulative incidence of all-cause death was higher in Quartile 4 throughout the entire follow-up period (19.9%, 24.9%, 28.8%, and 41.5% at 5-year, P < 0.0001), as well as both within and beyond 30-day. After adjustment, the excess risk of Quartile 4 relative to Quartile 1 for all-cause death remained significant (HR 1.60, 95% CI 1.29-2.03). Similarly, the excess risk of Quartile 4 relative to Quartile 1 for recurrent VTE was significant (HR 1.57, 95% CI 1.02-2.41), which was more prominent in the cancer subgroup. The dominant causes of death in Quartile 4 were pulmonary embolism within 30-day, and cancer beyond 30-day. In conclusions, in VTE patients, elevated D-dimer levels at diagnosis were associated with the increased risk for both short-term and long-term mortality. The higher mortality risk of patients with highest D-dimer levels was driven by the higher risk for fatal PE within 30-day, and by the higher risk for cancer death beyond 30-day. Elevated D-dimer levels were also associated with the increased risk for long-term recurrent VTE, which was more prominent in patients with active cancer.

Antithrombotic and Anti-Inflammatory Effects of Fondaparinux and Enoxaparin in Hospitalized COVID-19 Patients: The FONDENOXAVID Study

Background

Since the outbreak of novel coronavirus SARS-CoV2 around the world, great attention has been paid to the effects of such antithrombotic drugs as heparinoids, because they have antiviral action in vitro and antithrombotic actions in vivo. We conducted a retrospective analysis in inpatients with confirmed COVID-19 on the anti-inflammatory and antithrombotic effects of enoxaparin and fondaparinux at prophylactic doses.

Methods

This retrospective cohort study used patients with confirmed COVID-19 during the first months of the Italian outbreak from February 18 to April 30, 2020. Our aim was to compare clinical characteristics, prophylactic treatment, markers of inflammation, and thrombotic outcomes in inpatients positive for SARS-CoV2 during hospitalization associated with thromboprophylaxis with enoxaparin (40 mg or 60 mg once daily) or fondaparinux (2.5 mg once daily). Statistical analysis was conducted with using MatLab R2016B and ad hoc functions.

Results

There were no significatant differences in clinical characteristics between patients that used enoxaparin or fondaparinux as thromboprophylaxis for SARS-CoV2. No differences were found in D-dimer and fibrinogen levels either, which were used as markers of inflammation during the infection at testing on admission and after 3 weeks.Significant differences in CRP, IL6, and LDH were found in patients after 21 days’ treatment.

Discussion

Increased levels of fibrinogen and D-dimer in patients with confirmed COVID-19 have been reported in several studies. Our results showed that anti-inflammatory effects of fondaparinux and enoxaparin after 3 weeks of prophylactic treatment were similar when levels of fibrinogen and D-dimer were considered. Furthermore, levels of CRP showed a decrease in patients treated with enoxaparin and fondaparinux, although the decrease in the fondaparinux group seems to be more relevant.

Elevated D-dimer levels on admission are associated with severity and increased risk of mortality in COVID-19: A systematic review and meta-analysis

BACKGROUND

In this systematic review and meta-analysis, we aimed to investigate the correlation of D-dimer levels measured on admission with disease severity and the risk of death in patients with coronavirus disease 2019 (COVID-19) pneumonia.

MATERIALS AND METHODS

We performed a comprehensive literature search from several databases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in abstracting data and assessing validity. Quality assessment was performed using the Newcastle-Ottawa quality assessment scale (NOS). D-dimer levels were pooled and compared between severe/non-severe and surviving/non-surviving patient groups. Weighted mean difference (WMD), risk ratios (RRs) and 95% confidence intervals (CIs) were analyzed.

RESULTS

Thirty-nine studies reported on D-dimer levels in 5750 non-severe and 2063 severe patients and 16 studies reported on D-dimer levels in 2783 surviving and 697 non-surviving cases. D-dimer levels were significantly higher in patients with severe clinical status (WMD: 0.45 mg/L, 95% CI: 0.34-0.56; p < 0.0001). Non-surviving patients had significantly higher D-dimer levels compared to surviving patients (WMD: 5.32 mg/L, 95% CI: 3.90-6.73; p < 0.0001). D-dimer levels above the upper limit of normal (ULN) was associated with higher risk of severity (RR: 1.58, 95% CI: 1.25-2.00; p < 0.0001) and mortality (RR: 1.82, 95% CI: 1.40-2.37; p < 0.0001).

CONCLUSION

Increased levels of D-dimer levels measured on admission are significantly correlated with the severity of COVID-19 pneumonia and may predict mortality in hospitalized patients.

Impact of atrial fibrillation/flutter on the in-hospital mortality of surgical patients - Results from the German nationwide cohort

BACKGROUND

To investigate the impact of atrial fibrillation/flutter (AF) on adverse in-hospital outcomes in hospitalized surgical patients.

METHODS

The nationwide German inpatient sample of the years 2005-2018 was used for this analysis. Surgical patients were stratified by AF and compared. Logistic regression models were used to investigate the impact of AF on in-hospital outcomes.

RESULTS

In total, 96,589,627 hospitalizations with surgery were included in the present analysis in Germany (2005-2018). Among these, 6,680,261 were additionally coded with AF (6.9%). In-hospital death rate was substantially higher in surgical patients with AF (6.3%) than without (1.1%). Proportion of surgical patients with AF increased from 4.8% in 2005 to 8.9% in 2018, whereas in-hospital mortality decreased from 7.6% to 5.6%. For further analysis of the year 2014, 7,043,514 hospitalized surgical patients (54.5% females, 31.6% aged ≥0 years) were included in the analysis. Of these, 546,019 patients (7.8%) were diagnosed with AF. Overall, 1.4% of the surgical patients and 5.8% of the surgical patients with AF died in-hospital. Surgical patients with coded AF were in median 20 years older (57.0 [37.0-72.0] vs. 77.0 [72.0-83.0] years, P < 0.001), had more often comorbidities such as heart failure (31.3% vs. 3.8%, P < 0.001). All-cause death (RR 6.14 (95%CI 6.05-6.22), P < 0.001) occurred more often in patients with AF than without. AF was an important predictor for in-hospital death (OR 1.58 [95%CI 1.56-1.61], P < 0.001) independent of age, sex and comorbidities.

CONCLUSIONS

The proportion of AF increased from 2005 to 2018 in surgical patients. AF was an independent risk factor for in-hospital death in these patients.

D-dimer as a thrombus biomarker for predicting 2-year mortality after percutaneous coronary intervention

Background:

D-dimer has predictive value for mortality in some diseases. This study aimed to evaluate the correlation between D-dimer and mortality in patients undergoing percutaneous coronary intervention (PCI).

Methods:

We examined 10,724 consecutive patients who underwent PCI between January 2013 and December 2013. The primary endpoint was all-cause mortality, and the secondary endpoint was cardiac mortality. Patients were divided according to the median D-dimer level of 0.28 μg/ml. Multivariable model were including age, sex, and risk factors after stepwise selection.

Results:

After a 2-year follow up, 8565 patients with D-dimer data were analyzed. There were 116 (1.35%) all-cause deaths and 64 (0.75%) cardiac deaths. D-dimer levels were significantly higher in the all-cause mortality group [0.42 (0.29, 0.68) μg/ml] and cardiac mortality group [0.48 (0.30, 0.81) μg/ml] than in the survival group [0.28 (0.20, 0.41) μg/ml] (both p < 0.001). Multivariate-adjusted Cox hazard analysis showed that high D-dimer levels (⩾0.28 μg/ml) were significantly associated with all-cause mortality in the total population [hazard ratio (HR): 2.35, 95% confidence interval (CI): 1.44–3.84, p = 0.001], acute coronary syndrome (ACS) subgroup (HR: 1.91, 95% CI: 1.08–3.38, p = 0.027), and stable coronary artery disease (SCAD) subgroup (HR: 3.82, 95% CI: 1.45–10.10, p = 0.007). High D-dimer levels were significantly associated with cardiac mortality in the total population (HR: 3.44, 95% CI: 1.61–7.36, p = 0.001) and the ACS subgroup (HR: 3.33, 95% CI: 1.38–8.03, p = 0.007), but not in the SCAD subgroup (HR: 3.68, 95% CI: 0.80–16.91, p = 0.094).

Conclusions:

D-dimer levels are independently associated with 2-year all-cause mortality and cardiac mortality in patients undergoing PCI.

D-dimer levels enhance the discriminatory capacity of bleeding risk scores for predicting in-hospital bleeding events in acute pulmonary embolism

INTRODUCTION

Bleeding is a major complication of anticoagulation in acute pulmonary embolism (APE) while estimating individual bleeding risk remains challenging. Elevated D-dimer levels (DD) have been shown to predict bleeding events.

OBJECTIVES

(1) direct comparison of the capacity of bleeding risk prediction scores (VTE-BLEED, RIETE, HAS-BLED, HEMORR₂HAGES) to prognosticate in-hospital bleeding events in the acute phase of APE in a real-life population of APE patients;(2) augmentation of the discriminative capacity of fore mentioned scores with DD.

MATERIALS

Post-hoc analysis of a prospective observational study. DD levels were measured using the VIDAS D-dimer Exclusion test. Receiver operating characteristic curves, areas under the curve (AUC) for bleeding prediction were calculated for scores and DD. Bleeding scores+DD were compared using an established index quantifying the reclassification of patients (net reclassification index, NRI).

RESULTS

310 APE patients were included. 35(11.3%) bleeding events occurred (hematomas, GI, urinary tract, retroperitoneal, uterine, CNS, respiratory tract): 17 major (MB) and 18 clinically-relevant non-major bleedings (CRNMB), none were fatal. All scores had satisfactory AUCs (0.754-0.767), except HAS-BLED (AUC = 0.512; 0.455-0.569). DD were higher in patients with bleeding events (29,911 ng/ml vs. 4805 ng/ml, p = .031), AUC 0.621(0.520-0.721), p = .02. DD = 5750 ng/ml was characterized by OR = 2.3(95%CI 1.05-5.0) for all bleeding events. Adding DD improved the discriminatory capacity of tested scores in the non-high risk of bleeding category, NRI 0.07-03.

CONCLUSIONS

Of the tested scores RIETE, HEMORR₂HAGES, VTE-BLEED performed best at identifying APE patients at risk of in-hospital bleeding complications. DD levels may predict in-hospital bleeding events and may improve identifying patients classified as non-high risk who experience bleeding complications.

D-Dimer Measured at Diagnosis of Venous Thromboembolism is Associated with Risk of Major Bleeding

Identification of patients at risk of major bleeding is pivotal for optimal management of anticoagulant therapy in venous thromboembolism (VTE). Studies have suggested that D-dimer may predict major bleeding during anticoagulation; however, this is scarcely investigated in VTE patients. We aimed to investigate the role of D-dimer, measured at VTE diagnosis, as a predictive biomarker of major bleeding. The study population comprised 555 patients with a first community-acquired VTE (1994-2016), who were identified among participants from the Tromsø study. Major bleeding events were recorded during the first year after VTE and defined according to the criteria of the International Society on Thrombosis and Haemostasis. Cox-regression was used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) adjusted for age, sex, and duration of anticoagulant therapy. In total, 29 patients experienced major bleeding (incidence rate: 5.7/100 person-years, 95% CI: 4.0-8.2). The major bleeding risk was highest during the first 3 months, especially in patients with D-dimer ≥8.3 µg/mL (upper 20th percentile), with 28.8 major bleedings/100 person-years (95% CI: 13.7-60.4). Patients with D-dimer ≥8.3 µg/mL had a 2.6-fold (95% CI: 1.1-6.6) higher risk of major bleeding than patients with D-dimer ≤2.3 µg/mL (lower 40th percentile). Major bleeding risk according to D-dimer ≥8.3 versus ≤2.3 µg/mL was particularly pronounced among those with deep vein thrombosis (HR: 4.6, 95% CI: 1.3-16.2) and provoked events (HR: 4.2, 95% CI: 1.0-16.8). In conclusion, our results suggest that D-dimer measured at diagnosis may serve as a predictive biomarker of major bleeding after VTE, especially within the initial 3 months.

Aggressive Treatment of Intermediate-Risk Patients with Acute Symptomatic Pulmonary Embolism

Contemporary studies of acute pulmonary embolism (PE) have evaluated the role of thrombolytics in intermediate-risk PE. Significant findings are that thrombolytic therapy may prevent hemodynamic deterioration and all-cause mortality but increases major bleeding. Benefits and harms are finely balanced with no convincing net benefit from thrombolytic therapy among unselected patients. Among patients with intermediate risk PE, additional prognostic factors or subtle hemodynamic changes might alter the risk-benefit assessment in favor of thrombolytic therapy before obvious hemodynamic instability.

d-Dimer Assessment Improves the Simplified Pulmonary Embolism Severity Index for In-Hospital Risk Stratification in Acute Pulmonary Embolism

d-dimer (DD) levels are used in the diagnostic workup of suspected acute pulmonary embolism (APE), but data on DD for early risk stratification in APE are limited. In this post hoc analysis of a prospective observational study of 270 consecutive patients, we aimed to optimize the discriminant capacity of the simplified pulmonary embolism severity index (sPESI), an APE risk assessment score currently used, by combining it with DD for in-hospital adverse event prediction. We found that DD levels were higher in patients with complicated versus benign clinical course 7.2 mg/L (25th-75th percentile: 4.5-27.7 mg/L) versus 5.1 mg/L (25th-75th percentile: 2.1-11.2 mg/L), P = .004. The area under the curve of DD for serious adverse event (SAE) was 0.672, P = .003. d-dimer =1.35 mg/L showed 100% negative predictive value for SAE and identified 11 sPESI ≥1 patients with a benign clinical course, detecting the 1 patient with SAE from sPESI = 0. d-dimer >15 mg/L showed heart rate for SAE 3.04 (95% confidence interval [CI]: 1-9). A stratification model which with sPESI + DD >1.35 mg/L demonstrated improved prognostic value when compared to sPESI alone (net reclassification improvement: 0.085, P = .04). d-dimer have prognostic value, values <1.35 mg/L identify patients with a favorable outcome, improving the prognostic potential of sPESI, while DD >15 mg/L is an independent predictor of SAE.

D-Dimer and thrombus burden in acute pulmonary embolism

BACKGROUND

Thrombus burden in pulmonary embolism (PE) is associated with higher D-Dimer-levels and poorer prognosis. We aimed to investigate i) the influence of right ventricular dysfunction (RVD), deep venous thrombosis (DVT), and high-risk PE-status on D-Dimer-levels and ii) effectiveness of D-Dimer to predict RVD in normotensive PE patients.

METHODS

Overall, 161 PE patients were analyzed retrospectively, classified in 5 subgroups of thrombus burden according to clinical indications and compared regarding D-Dimer-levels. Linear regression models were computed to investigate the association between D-Dimer and the groups. In hemodynamically stable PE patients, a ROC curve was calculated to assess the effectiveness of D-Dimer for predicting RVD.

RESULTS

Overall, 161 patients (60.9% females, 54.0% aged >70 years) were included in this analysis. The D-Dimer-level was associated with group-category in a univariate linear regression model (β 0.050 (95%CI 0.002-0.099), P = .043). After adjustment for age, sex, cancer, and pneumonia in a multivariate model we observed an association between D-Dimer and group-category with borderline significance (β 0.047 (95%CI 0.002-0.096), P = .058). The Kruskal-Wallis test demonstrated that D-Dimer increased significantly with higher group-category. In 129 normotensive patients, patients with RVD had significantly higher D-Dimer values compared to those without (1.73 (1.11/3.48) vs 1.17 (0.65/2.90) mg/l, P = .049). A ROC curve showed an AUC of 0.61, gender non-specific, with calculated optimal cut-off of 1.18 mg/l. Multi-variate logistic regression model confirmed an association between D-Dimer >1.18 mg/l and RVD (OR2.721 (95%CI 1.196-6.190), P = .017).

CONCLUSIONS

Thrombus burden in PE is related to elevated D-Dimer levels, and D-Dimer values >1.18 mg/l were predictive for RVD in normotensive patients. D-Dimer levels were influenced by DVT, but not by cancer, pneumonia, age, or renal impairment.

Rapid on-site evaluation of routine biochemical parameters to predict right ventricular dysfunction in and the prognosis of patients with acute pulmonary embolism upon admission to the emergency room

INTRODUCTION

Patients with acute pulmonary embolism(APE)who present with right ventricular dysfunction (RVD) have a worse prognosis. This study aimed to evaluate the value of routine biochemical parameters in predicting RVD and 30-day mortality in patients with APE.

METHODS

We retrospectively collected the clinical data for 154 enrolled patients, including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), D-dimer, cardiac troponin I (cTnI), and N-terminal pro-brain natriuretic peptide (NT-proBNP). We analyzed the correlation between RVD and the parameters and conducted a receiver operating characteristic (ROC) curve to confirm the cut-off values for predicting RVD and 30-day mortality. Formulas were built with relevant parameters to predict RVD and 30-day mortality.

RESULTS

Age, NLR, PLR, D-dimer, the ratio of cTnI (+), and NT-proBNP (+) were significantly higher in RVD (+) patients. The ratio of cTnI (+) and NT-proBNP (+) in 30-day mortality (+) patients was significantly higher than that in 30-day mortality (-) patients. According to the logistic regression analysis, NLR, cTnI (+), and NT-proBNP (+) correlated with RVD. The formula for the RVD risk score is 0.072 × NLR+1.460 × NT-proBNP (+)+2.113 × cTnI (+), and the area under the curve (AUC) = 0.890 (95% CI: 0.839-0.941, P = .001). The formula for the 30-day mortality risk score is 0.115 × NLR + 2.046 × NT-proBNP (+) + 1.946 × cTnI (+) -0.016 × PLR, and the AUC = 0.903 (95% CI: 0.829-0.976, P = .001).

CONCLUSIONS

The rapid on-site evaluation of routine biochemical parameters, including NLR, cTnI, and NT-proBNP levels, and the formula developed using these parameters are valuable for predicting RVD and 30-day mortality in patients with APE.

Terapia fibrinolítica sistêmica no tromboembolismo pulmonar

O tromboembolismo pulmonar permanece como um grande desafio terapêutico para os médicos especialistas, pois, apesar de todo investimento e desenvolvimento em seu diagnóstico, profilaxia e tratamento, essa condição continua sendo a principal causa de morte evitável em ambiente hospitalar. Ainda restam muitas dúvidas em relação a qual perfil de paciente vai se beneficiar de fato da terapia fibrinolítica sistêmica, sem ficar exposto a um grande risco de sangramento. A estratificação de risco e a avaliação do prognóstico do evento, através de escores clínicos de insuficiência ventricular direita, marcadores de dilatação e disfunção do ventrículo direito e avaliação da massa trombótica, associados ou de forma isolada, são ferramentas que podem auxiliar na identificação do paciente que irá se beneficiar dessa terapia. Os únicos consensos em relação à terapia fibrinolítica no tratamento do tromboembolismo pulmonar são: não deve ser indicada de forma rotineira; nenhum dos escores ou marcadores, isoladamente, devem justificar seu uso; e os pacientes com instabilidade hemodinâmica são os mais beneficiados. Além disto, deve-se avaliar cada caso em relação ao risco de sangramento, especialmente no sistema nervoso central.

Risk factors for pulmonary embolism in patients preliminarily diagnosed with community-acquired pneumonia: a prospective cohort study

D-dimer levels are increased in patients with acute pulmonary embolism (PE). However, D-dimer levels are also increased in patients with community-acquired pneumonia (CAP). The aim of this prospective cohort study was to examine the incidence and clinical features of patients preliminarily diagnosed with CAP and with increased D-dimer levels, and who finally were diagnosed with PE. Patients diagnosed with CAP and hospitalized in the Respiratory Department of the Tenth People's Hospital Affiliated to Tongji University between May 2011 and May 2013 were enrolled. D-dimer levels were measured routinely after admission. For patients with increased D-dimer levels, those suspected with PE underwent computed tomography pulmonary angiography (CTPA). A total of 2387 patients with CAP was included: 724 (30.3 %) had increased D-dimer levels (median of 0.91 mg/L). CTPA was performed for 139 of the 724 patients (median D-dimer levels of 1.99 mg/L). Among the 139 patients, 80 were diagnosed with PE, and 59 without PE; D-dimer levels were 2.83 and 1.41 mg/L, respectively (p < 0.05). Multivariate analysis showed that age, coronary heart disease, chronic obstructive pulmonary disease (COPD), lower limb varicosity, chest pain, shortness of breath, hemoptysis, fever, and increased levels of troponin I were independent risk factors for PE. Presentation of PE and CAP are similar. Nevertheless, these results indicated that for hospitalized patients with CAP and elevated D-dimer levels, PE should be considered for those >60 years; with CHD, COPD, or lower limb varicosity; with chest pain, shortness of breath, hemoptysis, increased troponin I, or low fever.

Variable Resistance to Plasminogen Activator Initiated Fibrinolysis for Intermediate-Risk Pulmonary Embolism

Background

We examine the clinical significance and biomarkers of tissue plasminogen activator (tPA)-catalyzed clot lysis time (CLT) in patients with intermediate-risk pulmonary embolism (PE).

Methods

Platelet-poor, citrated plasma was obtained from patients with PE. Healthy age- and sex-matched patients served as disease-negative controls. Fibrinogen, α₂-antiplasmin, plasminogen, thrombin activatable fibrinolysis inhibitor (TAFI), plasminogen activator Inhibitor 1 (PAI-1), thrombin time and D-dimer were quantified. Clotting was induced using CaCl₂, tissue factor, and phospholipid. Lysis was induced using 60 ng/mL tPA. Time to 50% clot lysis (CLT) was assessed by both thromboelastography (TEG) and turbidimetry (A405).

Results

Compared with disease-negative controls, patients with PE exhibited significantly longer mean CLT on TEG (+2,580 seconds, 95% CI 1,380 to 3,720 sec). Patients with PE and a short CLT who were treated with tenecteplase had increased risk of bleeding, whereas those with long CLT had significantly worse exercise tolerance and psychometric testing for quality of life at 3 months. A multivariate stepwise removal regression model selected PAI-1 and TAFI as predictive biomarkers of CLT.

Conclusion

The CLT from TEG predicted increased risk of bleeding and clinical failure with tenecteplase treatment for intermediate-risk PE. Plasmatic PAI-1 and TAFI were independent predictors of CLT.

Subsegmental pulmonary embolism: A narrative review

Through the introduction of computed tomography pulmonary angiography (CTPA) for diagnosis of the pulmonary embolism (PE), the high sensitivity of this diagnostic tool led to detecting peripheral filling defects as small as 2-3mm, termed as subsegmental pulmonary embolism (SSPE). However, despite these substantial increases in diagnosis of small pulmonary embolism, there are minimal changes in mortality. Moreover, SSPE patients generally are hemodynamically stable with mild clinical presentation, lower serum level of biomarkers, lower incidence of associated proximal DVTs and less frequent echocardiographic changes compared to the patients with emboli located in more central pulmonary arteries. However, the pros and cons of anticoagulant therapy versus non-treating, monitoring protocol and exact long term outcome of these patients are still unclear. In this article we review existing evidence and provide an overview of what is known about the diagnosis and management of subsegmental pulmonary embolism.

D-dimer for risk stratification in haemodynamically stable patients with acute pulmonary embolism

PURPOSE

Patients with submassive pulmonary embolism (PE) have a higher short-term mortality than those with low-risk PE. Rapid identification of submassive PE is important for adequate treatment of non-massive PE. We aimed to investigate the utility of D-dimer for the prediction of submassive PE stadium in normotensive PE patients.

PATIENTS AND METHODS

Normotensive PE patients were classified into submassive or low-risk PE groups. In addition to the comparison of the groups, area under the curve (AUC) and D-dimer cut-off for the prediction of submassive PE stadium, multi-variate logistic regression for association between D-dimer values above this cut-off and submassive PE stadium were also calculated.

RESULTS

The data of 129 normotensive PE patients (59.7% women, mean age 70.0 years (60.7/81.0)) were analysed retrospectively. Patients with submassive PE were older (75.0 years (61.7/81.0) vs. 66.5 years (55.7/74.2), P=0.026) and more frequently female (63.6% vs. 53.8%, P=0.35). Heart rate (100.0beats/min (85.0/108.0) vs. 80.0beats/min (70.0/96.2), P<0.0001), systolic pulmonary-artery pressure (41.55±16.79mmHg vs. 22.62±14.81mmHg, P<0.0001), and D-dimer (2.00mg/l (1.09/3.98) vs. 1.21mg/l (0.75/1.99), P=0.011) were higher in patients with submassive PE. D-dimer values >1.32mg/l were indicative of submassive PE and shock-index ≥0.7. The effectiveness (AUC) of the test was 0.63 for submassive PE and 0.64 for shock-index ≥0.7. D-dimer values >1.32mg/l were associated with submassive PE stadium (OR 3.81 (95% CI: 1.74-8.35), P=0.00083) as well as with systolic blood pressure (OR 0.98 (95% CI: 0.97-0.99), P=0.033), heart rate (OR 1.02 (95% CI: 1.00-1.04), P=0.023) and shock-index value (OR 15.89 (95% CI: 1.94-130.08), P=0.0099).

CONCLUSIONS

D-dimer values >1.32mg/l are indicative of submassive PE stadium and shock-index ≥0.7. Efficacy of D-dimer for predicting submassive PE stadium was only weak to moderate.

D-dimer levels and 90-day outcome in patients with acute pulmonary embolism with or without cancer

BACKGROUND

The prognostic value of D-dimer testing in patients with acute pulmonary embolism (PE) has not been thoroughly studied.

METHODS

We used the RIETE Registry data to assess the 90-day prognostic value of increased IL Test D-dimer levels at baseline in patients with PE, according to the presence or absence of cancer.

RESULTS

As of May 2013, 3,283 patients with acute PE underwent D-dimer testing using IL Test D-dimer. Among 2,588 patients without cancer, those with D-dimer levels in the highest quartile had a higher rate of fatal PE (2.6% vs. 0.9%; p=0.002), fatal bleeding (1.1% vs. 0.3%; p=0.017) and all-cause death (9.1% vs. 4.4%; p<0.001) at 90 days compared with those with levels in the lowest quartiles. Among 695 patients with cancer, those with levels in the highest quartile had a similar rate of fatal PE or fatal bleeding but higher mortality (35% vs. 24%; p<0.01). On multivariate analysis, non-cancer patients with D-dimer levels in the highest quartile had an increased risk for fatal PE (odds ratio [OR]: 3.3; 95% CI: 1.6-6.6), fatal bleeding (OR: 4.3; 95% CI: 1.4-13.7) and all-cause death (OR: 2.1; 95% CI: 1.4-3.1) compared with patients with levels in the lowest quartiles.

CONCLUSIONS

Non-cancer patients with acute PE and IL Test D-dimer levels in the highest quartile had an independently higher risk for fatal PE, fatal bleeding and all-cause death at 90 days than those with levels in the lowest quartiles. In patients with cancer, D-dimer levels failed to predict fatal PE or fatal bleeding.

Magnitude of D-dimer matters for diagnosing pulmonary embolus

OBJECTIVE

The objective of this study is to determine whether the magnitude of the D-dimer correlates with a higher likelihood of pulmonary embolus (PE).

METHODS

We performed an electronic chart review at our academic, tertiary care center, annual emergency department (ED) census greater than 100000. All patients with a chest computed tomographic (CT) scan with intravenous contrast and an elevated D-dimer level obtained in the ED between January 2001 and July 2008 were identified. Specific, predetermined, predefined data elements including sex, age, D-dimer level, and final ED diagnosis were recorded by a hypothesis-blinded extractor using a preformatted data form. D-dimer level less than 0.58 μg/mL constitutes the normal laboratory reference range for our turbidometric D-dimer assay. Data were analyzed using standard statistical methods, and a linear regression analysis was performed for correlation analysis of D-dimer and diagnosis of PE.

RESULTS

We identified 544 subjects who had both a chest CT scan performed and an elevated D-dimer level obtained in the ED. Fifty-eight subjects (10.7%; mean D-dimer, 4.9 μg/mL) were diagnosed with PE, and 486 (89.3%; mean D-dimer, 2.0) did not have a PE. The percentages of PE diagnoses for D-dimers in the ranges 0.58 to 1.0, 1.0 to 2.0, 2.0 to 5.0, 5.0 to 20.0, and greater than 20.0 (n = 11) were 3.6%, 8.0%, 16.2%, 35.3%, and 45.5%, respectively. The positive predictive value of PE for D-dimer level cutoffs of greater than 0.58, greater than 1.0, greater than 2.0, greater than 5.0, and greater than 20.0 was 10.7%, 14.6%, 22.2%, 37.8%, and 45.5%, respectively. Increasing D-dimer values were strongly correlated with the presence of PE (odds ratio, 1.1685 per stratum; P < .001).

CONCLUSION

Increasing magnitude of D-dimer correlates with increasing likelihood of PE diagnosed by CT angiography.

Novel biomarkers for risk stratification and identification of life-threatening cardiovascular disease: troponin and beyond

Chest pain and other symptoms that may represent acute coronary syndromes (ACS) are common reasons for emergency department (ED) presentations, accounting for over six million visits annually in the United States [1]. Chest pain is the second most common ED presentation in the United States. Delays in diagnosis and inaccurate risk stratification of chest pain can result in serious morbidity and mortality from ACS, pulmonary embolism (PE), aortic dissection and other serious pathology.

Because of the high morbidity, mortality, and liability issues associated with both recognized and unrecognized cardiovascular pathology, an aggressive approach to the evaluation of this patient group has become the standard of care. Clinical history, physical examination and electrocardiography have a limited diagnostic and prognostic role in the evaluation of possible ACS, PE, and aortic dissection, so clinicians continue to seek more accurate means of risk stratification. Recent advances in diagnostic imaging techniques particularly computed-tomography of the coronary arteries and aorta, have significantly improved our ability to diagnose life-threatening cardiovascular disease.

In an era where health care utilization and cost are major considerations in how disease is managed, it is crucial to risk-stratify patients quickly and efficiently. Historically, biomarkers have played a significant role in the diagnosis and risk stratification of several cardiovascular disease states including myocardial infarction, congestive heart failure, and pulmonary embolus. Multiple biomarkers have shown early promise in answering questions of risk stratification and early diagnosis of cardiovascular pathology however many do not yet have wide clinical availability. The goal of this review will be to discuss these novel biomarkers and describe their potential role in direct patient care.

Medical emergencies: pulmonary embolism and acute severe asthma

In this, the second of two articles covering specific medical emergencies, we discuss the definitions, epidemiology, pathophysiology, acute and chronic management of pulmonary embolus and acute severe asthma.

d-Dimer and simplified pulmonary embolism severity index in relation to right ventricular function

BACKGROUND

Right ventricular (RV) involvement in pulmonary embolism (PE) is an ominous sign. The aim of this study was to investigate the extent to which the d-dimer level or simplified PE severity index (sPESI) indicates RV dysfunction in patients with preserved systemic arterial pressure.

METHODS

Right ventricular function was studied in 34 consecutive patients with acute nonmassive PE by echocardiography including Doppler tissue imaging within 24 hours after arrival to the hospital. d-Dimer and sPESI were assessed upon arrival.

RESULTS

d-Dimer correlated with RV pressure (Rs, 0.60; P < .001) and pulmonary vascular resistance (PVR; Rs, 0.68; P < .0001) and tended to be related to myocardial performance index (MPI; Rs, 0.31; P = .067). Compared to a level less than 3.0 mg/L, patients with d-dimer 3.0 mg/L or higher had lower systolic tricuspid annular velocity (11.3 ± 2.7 vs 13.5 ± 2.7 cm/s; P < .05), a prolonged MPI (0.8 ± 0.3 vs 0.5 ± 0.2; P < .01), increased RV pressure (58 ± 13 vs 37 ± 12 mm Hg; P < .001), and increased PVR (3.3 ± 1.1 vs 1.8 ± 0.4 Woods units; P < .001). Patients in the high-risk sPESI group had higher filling pressure than those in the low risk sPESI group.

CONCLUSIONS

In the acute stage of PE, a d-dimer level 3 mg/L or higher may identify nonmassive PE patients with RV dysfunction and thereby help to determine their risk profile. We found no additional value for sPESI in this context.

Prognostic value of D-dimer in stable patients with pulmonary embolism

Prognosis of pulmonary embolism (PE) based on levels of D-dimer has shown mixed results, and data on in-hospital prognosis of stable patients are sparse. We assessed in-hospital prognosis in 292 stable patients with PE based on retrospective chart review using an arbitrarily selected value of D-dimer ≥5000 ng/mL as cut-off level. In-hospital mortality from PE was 0% (0 of 222) with D-dimer <5000 ng/mL compared with 2.9% (2 of 70) with D-dimer ≥5000 ng/mL (P = .06). In-hospital all-cause mortality was 2.3% (5 of 222) with D-dimer <5000 ng/mL compared with 2.9% (2 of 70) with D-dimer ≥5000 ng/mL (NS). Markedly elevated levels of D-dimer, therefore, did not indicate a high mortality from PE or all-cause mortality during hospitalization.

Outcomes considered most important by emergency physicians when determining disposition of patients with pulmonary embolism

Purpose

Clinical decision rules for the disposition of patients with pulmonary embolism (PE) are typically validated against an outcome of 30-day mortality or disease recurrence. There is little justification for this time frame, nor is it clear whether this outcome reflects emergency department (ED) decision making.

Aims

To determine which outcomes emergency physicians (EP) consider most relevant to disposition decisions.

Methods

Survey of attending EPs in geographically diverse US states using acute PE as the diagnostic framework. Responses required single-answer multiple choice, a numerical percentage, rank-ordered responses, or a five-point Likert scale. We distributed the survey via e-mail to 608 EPs.

Results

We received responses from 292 (48%) EPs: 88% board certified, 91% trained in emergency medicine, and 70% work in academics. Respondents reported discharging 1% of patients with PE from the ED, but 21% reported being asked to do so by an admitting service. EPs were more interested in knowing 5-day (in hospital) outcomes [192/265, 72% (95% exact CI = 66%–78%)] than 30-day outcomes [39/261, 15% (95% exact CI = 11%–20%)] or 90-day outcomes [29/263, 11% (95% exact CI = 8%–15%)]. On a Likert scale, 212/241 (88%, 95% exact CI = 83%–92%) agreed or strongly agreed that they considered 5-day (in hospital) clinical deterioration when making a decision to admit or discharge a patient from the ED compared to 184/242 (76%, 95% exact CI = 70%–81%) and 73/242 (30%, 95% exact CI = 24%–36%) for 30 and 90 days, respectively. A wide variety of clinical outcomes beyond death or recurrent PE were considered indicative of clinical deterioration.

Conclusions

Five-day (in hospital) outcomes that incorporate a variety of clinical deterioration events are of interest to EPs when determining the disposition of ED patients with PE. Researchers should consider this when developing and validating clinical decision rules.

Risk stratification of normotensive patients with acute symptomatic pulmonary embolism

Treatment guidelines recommend strong consideration of thrombolysis in patients with acute symptomatic pulmonary embolism (PE) that present with arterial hypotension or shock because of the high risk of death in this setting. For haemodynamically stable patients with PE, the categorization of risk for subgroups may assist with decision-making regarding PE therapy. Clinical models [e.g. Pulmonary Embolism Severity Index (PESI)] may accurately identify those at low risk of overall death in the first 3 months after the diagnosis of PE, and such patients might benefit from an abbreviated hospital stay or outpatient therapy. Though some evidence suggests that a subset of high-risk normotensive patients with PE may have a reasonable risk to benefit ratio for thrombolytic therapy, single markers of right ventricular dysfunction (e.g. echocardiography, spiral computed tomography, or brain natriuretic peptide testing) and myocardial injury (e.g. cardiac troponin T or I testing) have an insufficient positive predictive value for PE-specific mortality to drive decision-making toward such therapy. Recommendations for outpatient treatment or thrombolytic therapy for patients with PE necessitate further development of prognostic models and conduct of clinical trials that assess various treatment strategies.

Clinical characteristics and outcome of inpatients versus outpatients with venous thromboembolism: findings from the RIETE Registry

BACKGROUND

Patients with venous thromboembolism (VTE) treated with anticoagulants are at risk of death from pulmonary embolism (PE) and/or bleeding. However, whether patients who develop VTE in hospital have a higher complication rate than those who develop VTE in an outpatient setting is unclear.

PATIENTS AND METHODS

RIETE is an ongoing, prospective registry of consecutive patients with acute, objectively confirmed, symptomatic VTE. We compared the 3-month incidence of fatal PE and fatal bleeding in patients in whom the VTE had developed while in hospital for another medical condition (inpatients) with those who presented to the emergency ward because of VTE (outpatients).

RESULTS

Up to April 2008, 22,133 patients with acute VTE were enrolled: 10,461 (47%) presented with PE, 11,672 with deep vein thrombosis. Overall, 6445 (29%) were inpatients. During the study period, those who developed VTE as inpatients had a significantly higher incidence of fatal PE (2.1% vs. 1.5%; odds ratio: 1.4; 95% CI: 1.1-1.7), overall death (7.0% vs. 5.4%; odds ratio: 1.3; 95% CI: 1.2-1.5), and major bleeding (2.9% vs. 2.1%; odds ratio: 1.4; 95% CI: 1.1-1.6) than outpatients. The incidence of fatal bleeding was not significantly increased (0.7% vs. 0.5%; odds ratio: 1.2; 95% CI: 0.9-1.8). In multivariable analysis, inpatient status was significantly associated with a higher risk for fatal PE (odds ratio: 1.3; 95% CI: 1.1-1.7).

CONCLUSIONS

VTE occurring in hospitalized patients carries a significantly higher risk for death of PE than in outpatients, underscoring the importance of VTE prevention strategies in the hospital setting.

Massive pulmonary embolism leading to cardiac arrest is associated with consumptive coagulopathy presenting as disseminated intravascular coagulation

SUMMARY BACKGROUND

A consumptive coagulopathy resembling disseminated intravascular coagulation (DIC) has been seen in patients with massive pulmonary embolism (PE). We hypothesized that a DIC-like condition is relevant in patients whose pulmonary embolism leads to cardiopulmonary arrest and cardiopulmonary resuscitation (CPR).

METHODS

This hypothesis was tested by the use of a database consisting of all cases of PE diagnosed at the Department of Emergency Medicine from June 1993 to October 2007. Out of 1018 cases with PE, 113 patients underwent CPR. In this cohort study, the resuscitated patients were compared with those with PE but without CPR.

RESULTS

Patients with PE and CPR had 3-fold higher D-dimer, prolonged prothrombin time (PT), reduced platelet counts and lower fibrinogen and antithrombin (AT) levels compared with PE patients without cardiac arrest (P < 0.001 for all). Among patients with PE and CPR, D-dimer was abnormal in 100%, PT in 44%, AT in 53%, fibrinogen in 19% and platelets in 25%. In comparison, PE without CPR was associated with abnormal D-dimer in 99%, abnormal PT in 15%, low AT in 6%, low fibrinogen in 1% and low platelets in 2%. Nine per cent of the resuscitated patients had a DIC score >or= 5, indicating overt DIC. The DIC score highly correlated with 1-year and in-hospital mortality.

CONCLUSIONS

Massive PE leading to CPR is associated with consumptive coagulopathy and overt DIC. In resuscitated patients, DIC markers may indicate pulmonary embolism as the underlying cause of arrest.

Relationship between disease severity and D-dimer levels measured with two different methods in pulmonary embolism patients

Pulmonary embolism (PE) is diagnosed with increasing frequency nowadays due to advances in the diagnostic methods and the increased awareness of the disease. There is a tendency to use non invasive diagnostic methods for all diseases. D-dimer is a fibrin degradation product. We aimed to detect the relationship between disease severity and the D-dimer levels measured with two different methods. We compared D-dimer levels in cases of massive vs. non-massive PE. A total of 89 patients who were diagnosed between 2006 and 2008 were included in the study. Group 1 included patients whose D-dimer levels were measured with the immunoturbidimetric polyclonal antibody method (D-dimerPLUS^®), while Group 2 patients made use of the immunoturbidimetric monoclonal antibody method (InnovanceD-DIMER^®). In each group, the D-dimer levels of those with massive and non-massive PE were compared, using the Mann Whitney U test. The mean age of Group 1 (25 F/26 M) was 56.0 ± 17.9 years, and that of Group 2 (22 F/16 M) was 52.9 ± 17.9 years. There was no statistical difference in gender and mean age between the two groups (p > 0.05). In Group 1, the mean D-dimer level of massive cases (n = 7) was 1444.9 ± 657.9 μg/L and that of nonmassive PE (n = 34) was 1304.7 ± 350.5 μg/L (p > 0.05). In Group 2, the mean D-dimer level of massive cases (n = 6) was 9.7 ± 2.2 mg/L and that of non-massive PE (n = 32) was 5.9 ± 1.3 mg/L (p < 0.05). The mean D-dimer levels of massive cases as measured with the immunoturbidimetric monoclonal antibody method were significantly higher. Pulmonary embolism patients whose D-dimer levels are higher (especially higher than 6.6 mg/L) should be considered as possibly having massive embolism. Diagnostic procedures and management can be planned according to this finding.

Sensitive and selective detection of free FXIII activation peptide: a potential marker of acute thrombotic events

Coagulation factor XIII (FXIII) stabilizes fibrin fibers and is therefore a major player in the maintenance of hemostasis. FXIII is activated by thrombin resulting in cleavage and release of the FXIII activation peptide (AP-FXIII). The objective of this study was to characterize the released AP-FXIII and determine specific features that may be used for its specific detection. We analyzed the structure of bound AP-FXIII within the FXIII A-subunit and interactions of AP-FXIII by hydrogen bonds with both FXIII A-subunit monomers. We optimized our previously developed AP-FXIII ELISA by using 2 monoclonal antibodies. We determined high binding affinities between the antibodies and free AP-FXIII and demonstrated specific binding by epitope mapping analyses with surface plasmon resonance and enzyme-linked immunosorbent assay. Because the structure of free AP-FXIII had been characterized so far by molecular modeling only, we performed structural analysis by nuclear magnetic resonance. Recombinant AP-FXIII was largely flexible both in plasma and water, differing significantly from the rigid structure in the bound state. We suggest that the recognized epitope is either occluded in the noncleaved form or possesses a structure that does not allow binding to the antibodies. On the basis of our findings, we propose AP-FXIII as a possible new marker for acute thrombotic events.