Value of Quantitative D-dimer Assays in Identifying Pulmonary Embolism: Implications from a Sequential Decision Model

Objectives: To examine the cost-effectiveness of a quantitative D-dimer assay for the evaluation of patients with suspected pulmonary embolism (PE) in an urban emergency department (ED).
Methods: The authors analyzed different diagnostic strategies over pretest risk categories on the basis of Wells criteria by using the performance profile of the ELISA D-dimer assay (over five cutoff values) and imaging strategies used in the ED for PE: compression ultrasound (CUS), ventilation–perfusion (VQ) scan (over three cutoff values), CUS with VQ (over three cutoff values), computed tomography (CT) angiogram (CTA) with pulmonary portion (CTP) and lower-extremity venous portion, and CUS with CTP. Data used in the analysis were based on literature review. Incremental costs and quality-adjusted-life-years were the outcomes measured.
Results: Computed tomography angiogram with pulmonary portion and lower-extremity venous portion without D-dimer was the preferred strategy. CUS-VQ scanning always was dominated by CT-based strategies. When CTA was infeasible, the dominant strategy was D-dimer with CUS-VQ in moderate- and high-Wells patients and was D-dimer with CUS for low-Wells patients. When CTP specificity falls below 80%, or if its overall performance is markedly degraded, preferred strategies include D-dimer testing. Sensitivity analyses suggest that pessimistic assessments of CTP accuracy alter the results only at extremes of parameter settings.
Conclusions: In patients in whom PE is suspected, when CTA is available, even the most sensitive quantitative D-dimer assay is not likely to be cost-effective. When CTA is not available or if its performance is markedly degraded, use of the D-dimer assay has value in combination with CUS and a pulmonary imaging study. These conclusions may not hold for the larger domain of patients presenting to the ED with chest pain or shortness of breath in whom PE is one of many competing diagnoses.     

Multi-center implementation of automated age-adjusted D-dimer results reduces unnecessary PE imaging

BackgroundSeveral previous studies have investigated the clinical utility of age-adjusted D-dimer cutoffs for diagnosing pulmonary embolism (PE).ObjectivesWe performed a pre/post implementation study, using data from a mid-Atlantic healthcare system comprising 6 hospitals and 400,000 ED visits to determine whether implementing age adjusted D-dimer cutoffs reduced the number of imaging tests performed.MethodsRetrospective study of all patients who had a D-dimer performed during ED visits between September 2015 to September 2018. On March 21, 2017, the D-dimer upper limit of normal system-wide was increased for patients over 50 to: Age (years) x 0.01μg/mL. D-dimer results were displayed as normal or high based on automated age adjustment. EHR Chart review was performed 1.5 years prior to implementation of age-adjusted D-dimer cutoffs, as well as 1.5 years after to evaluate mortality and test accuracy characteristics such as false negative rates. Comparisons were made using chi-square testing.Results22,302 D-dimers were performed pre-implementation of which 10,837 (48.6%) were positive resulting in 7218 (32.3%) imaging studies. After implementation of age-adjusted d-dimer, 25,082 were performed of which 10,851 (43.2%) were positive resulting in 7017 (28.0%) imaging studies. (pre: 48.6%, post: 43.2%; p < 0.01). A significantly lower proportion of patients had a positive d-dimer (pre: 48.6%, post: 43.2%; p < 0.01) and underwent imaging post-implementation (pre: 32.3%, post: 28.0%; p < 0.05) a relative risk reduction of 13.3. This absolute risk reduction of 4.4% is associated with 1104 less scans in the post-implementation group while still increasing test accuracy from 53.7% to 59.2% (p < 0.05).ConclusionImplementation of an automated age-adjusted D-dimer positive reference value reduced CT and V/Q imaging in this population by 4.4% while increasing test accuracy in a regional, heterogeneous six-hospital system.     

Comparison of the age-adjusted and clinical probability-adjusted D-dimer to exclude pulmonary embolism in the ED

Background

Diagnosing pulmonary embolism (PE) in the emergency department (ED) can be challenging because its signs and symptoms are non-specific.

Investigation of age-adjusted D-dimer using an uncommon assay

BackgroundUse of an age-adjusted D-dimer for the evaluation of acute pulmonary embolus (PE) has been prospectively validated in the literature and has become a practice recommendation from major medical societies. Most research on this subject involves the most common D-dimer assays reporting in Fibrinogen Equivalent Units (FEU) with a non-age-adjusted manufacturer-recommended cutoff of 500 ng/ml FEU. Limited research to date has evaluated age-adjustment in assays that report in D-Dimer Units (D-DU), which use a manufacturer-recommended cutoff of 230 ng/ml D-DU. Despite scant evidence, an age-adjusted formula using D-DU has been recently endorsed by the American College of Emergency Physicians (ACEP). This formula seems arbitrary in its derivation and unnecessarily deviates from existing thresholds, thus prompting the creation of our novel-age adjustment formula. The goal of this study was to retrospectively evaluate the test characteristics of our novel age-adjusted D-dimer formula using the D-DU assay in comparison to existing traditional and age-adjusted D-dimer thresholds for the evaluation of acute PE in the ED.MethodsThis was a retrospective chart review at an academic quaternary health system with three EDs and 195,000 combined annual ED visits. Only patients with D-dimer testing and CT PE protocol (CTPE) imaging were included. Admission and discharge diagnosis codes were used to identify acute PE. Outcome measures were sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) of an unadjusted traditional threshold (230) compared with both novel and ACEP-endorsed age adjusted thresholds, (Age × 5) ? 20 and Age × 5 if >50, respectively. Estimates with their exact 95% threshold were performed.Results4846 adult patients were evaluated from January 2012 to July 2017. Group characteristics include a mean age of 52 and a frequency of acute PE diagnosis by CTPE of 8.25%. Traditional D-dimer cutoff demonstrated a sensitivity of 99.8% (95% CI 98.6–100), specificity of 16.7% (95% CI 15.6–17.8) and NPV of 99.9% (95% CI 99.3–100). Our novel age-adjusted D-dimer thresholds had a sensitivity of 97.0% (95% CI 94.8–98.4), specificity of 27.9% (95% CI 26.6–29.2) and NPV of 99.0% (95% CI 98.3–99.5) with the ACEP-endorsed formula demonstrating similar test characteristics.ConclusionUse of an age-adjusted D-dimer on appropriately selected patients being evaluated for acute PE in the ED with a D-DU assay increases specificity while maintaining a high sensitivity and NPV. Both our novel formula and the ACEP-endorsed age-adjusted formula performed well, with our novel formula showing a trend towards improved testing characteristics.     

Utilization and Yield of Chest Computed Tomographic Angiography Associated with Low Positive D-dimer Levels

Background

It is unclear to what degree broadly applied D-dimer testing combined with a low threshold for imaging with even minimally positive results may be contributing to the utilization of chest computed tomographic angiography (CTA).

Study Objectives

To determine what proportion of chest CTAs for suspected pulmonary embolism (PE) were performed in the setting of minimally elevated D-dimer levels, and to determine the prevalence of PE in those patients when stratified by clinical risk.

Methods

Retrospective chart review of all patients who had chest CTA for the evaluation of suspected PE during the years 2002–2006 in a suburban community teaching hospital emergency department.

Results

There were 1136 eligible patient visits, of which 353 (31.1%) were found to have D-dimer levels in the low positive range (0.5–0.99 μg/mL). Of these 353 patients, 9 (2.6%; 95% confidence interval [CI] 0.9–4.2%) were diagnosed with PE. There were also 109 patients (9.6%) who had normal D-dimer levels (<0.5 μg/mL). Two of these 109 (1.8%; 95% CI 0–4.2%) were diagnosed with PE. When stratified by the Pulmonary Embolism Rule-out Criteria, 99 of 353 patients with low positive D-dimer levels (28.0%; 95% CI 23.4–32.7%), and 14 of 109 with normal D-dimer levels (12.8%; 95% CI 6.6–19.1%) were classified as low risk, none of whom had PE.

Conclusions

Nearly one-third of all chest CTAs were done for patients with minimally elevated D-dimer levels, and another 9.6% for patients with normal D-dimer levels with very low yield. Further research to define clinical criteria identifying patients with minimal risk of PE despite low positive D-dimer levels represents an opportunity to improve both patient safety and utilization efficiency of chest CTA.     

The impact of using different age-adjusted cutoffs of D-dimer in the diagnosis of pulmonary thromboembolism

BackgroundThis study was conducted to evaluate the relationship of age-adjusted D-dimer value with different coefficients in diagnosis of pulmonary embolism (PE) in geriatric patients.MethodsThe emergency admissions of the patients aged 65 and over with suspected PE during 2018 were reviewed retrospectively. The demographic characteristics, laboratory tests and radiologic findings of computed tomography pulmonary angiogram (CTPA) or single photon emission computed tomography ventilation/perfusion scintigraphy (V/Q) were recorded. The characteristics of the patients with PE were statistically compared with the patients without PE. The specificity and sensitivity for higher cut-off levels (age × 10–15) were presented.ResultsPE was detected in 39.2% (n = 246) of 628 patients aged 65 years and older included in the study. The multivariate analysis revealed that higher D-dimer level (OR = 1,00011; p < 0.001) and BUN level (OR = 1.025; p = 0.013) were independent risk factors for PE diagnosis in elderly patients. Diagnostic statistics for D-dimer cut-off levels selected from ROC analysis and calculated values as 10–15 times of age showed that if the D-dimer cut-off value used is chosen higher, lower sensitivity rates are obtained. Our results also indicated that the patients with malignancy, renal failure, central PE on CTPA and PE with high probability on SPECT VQ were presented with higher D-dimer values.ConclusionOur results do not support the use of higher D-dimer cut-off levels such as 15 times the age in geriatric population. The impact of the location of PE and comorbidities on the outcomes of these patients must be clarified for determining cut-offs with higher specificity.     

血浆D-二聚体对疑似肺栓塞患者诊断价值的研究

目的：探讨血浆 D-二聚体对对疑似肺栓塞患者的诊断价值。方法采用自动化免疫比浊法测定患者血浆D-二聚体水平。统计分析血浆D-二聚体诊断肺栓塞的敏感性、特异性、阴性及阳性预测值,并绘制ROC曲线以评价其诊断价值并对D-二聚体阴性排除肺栓塞价值进行分析。结果在317例疑似肺栓塞患者中D-二聚体＜500μg/L的患者73例,其中6例被诊断为肺栓塞。D-二聚体对肺栓塞的诊断的敏感性为95.86%（95%CI：91.27%～98.08%）,特异性为38.95%（95%CI：31.98%～41.41%）,阴性预测值为91.78%（95%CI：83.21%～96.18%）,阳性预测值为56.97%（95%CI：50.69%～63.02%）,诊断准确性为64.98%（95%CI：59.58%～70.03%）。ROC曲线下面积为0.674（95%CI：0.615～0.733）。结论 D-二聚体对肺栓塞的诊断具有较高的敏感性,阴性排除肺栓塞的准确性较高,但仍可受患者年龄、测试方法等的影响。     

Clinical probability score and D-dimer estimation lack utility in the diagnosis of childhood pulmonary embolism

Summary.  Background : Childhood pulmonary embolism (PE) causes significant mortality and evidence suggests that it is under-diagnosed. Clinical probability scores and D-dimer estimation to assess pre-test probability have not been studied in children with suspected PE. Patients/Methods : This retrospective cohort study evaluated Wells simplified probability score for PE in 50 children with PE and 25 PE negative control patients, and D-dimer values in 27 PE positive and 12 PE negative children. Results : PE positive and PE negative groups had similar rates of risk factors for venous thromboembolism (VTE). Wells simplified probability score showed a small difference between PE positive and PE negative children (median score: PE positive, 4.5; PE negative, 4; P  =   0.009), children with PE are more likely to obtain a 'PE likely' score (score > 4), P  =   0.012. The difference was of slightly greater significance when the Wells score was adjusted to account for pediatric normal ranges for heart rate, P  =   0.007, and signs/symptoms of upper limb DVT, P  =   0.006. Children with PE were as likely as PE negative patients to have a D-dimer value within the normal range (PE positive, 15%; PE negative, 25%; P  =   0.654). A combination of a 'PE unlikely' score and normal D-dimer value occurred in 1/12 (8%) of PE negative children. Conclusions : The Wells clinical probability score and D-dimer estimation may lack utility in the determination of pre-test probability of PE in children. Validation of a pediatric clinical probability score, incorporating D-dimer estimation, by prospective study, would be difficult as a result of the rarity of childhood PE.     

Pulmonary Embolism Rule-out Criteria vs D-dimer testing in low-risk patients for pulmonary embolism: a retrospective study

Study objectives

The Pulmonary Embolism Rule-out Criteria (PERC) score has shown excellent negative predictive value; however, its use in the European population with high prevalence of PE is controversial. In Europe, PERC is not part of routine practice. For low-risk patients, guidelines recommend D-dimer testing, followed if positive by imaging study. We aimed to study the rate of diagnosis of PE after D-dimer testing in PERC-negative patients that could have been discharged if PERC was applied.

Method

This was a multicenter retrospective study in Paris, France. We included all patients with a suspicion of PE who had D-dimer testing in the emergency department, low pre-test probability, and a negative PERC score (that was retrospectively calculated). Patients with insufficient record to calculate PERC score were excluded. The primary end point was the rate of PE diagnosis before discharge in this population. Secondary end points included rate of invasive imaging studies and subsequent adverse events.

Results

We screened 4301 patients who had D-dimer testing, 1070 of whom were PERC negative and could be analyzed. The mean age was 35 years and 46% were men. D-dimer was positive (> 500 ng/L) in 167 (16%) of them; CTPA or V/Q scan was performed in 153 (14%) cases. PE was confirmed in 5 cases (total rate 0.5%, 95% confidence interval 0.1%-1.1%). Fifteen patients (1%) experienced non-severe adverse events.

Conclusion

D-dimer testing in PERC-negative patients led to a diagnosis of PE in 0.5% of them, with 15% of patients undergoing unnecessary irradiative imaging studies.     

Outcomes of high pretest probability patients undergoing d-dimer testing for pulmonary embolism: a pilot study

ELISA (enzyme-linked immunosorbent assay) D-dimer testing is commonly used in the evaluation of possible pulmonary embolism (PE) in the emergency department, but is not recommended in high pretest probability patients. Whether a negative ELISA D-dimer can safely rule out PE in these patients is not known, as there have been no large studies comparing ELISA D-dimer results and outcomes in high pretest probability patients. This was a prospective observational pilot study of emergency department patients evaluated for PE. Patients evaluated for PE had pretest probability assessed by the Wells PE Score. High pretest probability was defined as: dichotomized Wells Score > 4 points and patients with trichotomized Wells Score > 6 points. Patients had an ELISA D-dimer ordered by the treating physician. Pulmonary embolism was defined as: positive computed tomography scan, high probability ventilation/perfusion scan, positive pulmonary angiogram, or PE on 3-month follow-up. We calculated sensitivity, specificity, positive and negative predictive value, and likelihood ratios for the ELISA D-dimer. We prospectively enrolled 541 patients who underwent D-dimer testing for PE, of whom 130 patients had Wells Score > 4 and 33 patients had Wells Score > 6 (not mutually exclusive). Of subjects with Wells Score > 4, 23 (18%) were diagnosed with PE and 40 (31%) had a negative D-dimer. No patient with Wells Score > 4 (sensitivity 100%, 95% confidence interval [CI] 82%–100%; specificity 37%, 95% CI 28%–47%) or Wells Score > 6 (sensitivity 100%, 95% CI 63%–100%; specificity 56%, 95% CI 35%–76%) who had a negative D-dimer was diagnosed with PE. The likelihood ratio for a negative D-dimer was 0 for both the Wells > 4, and Wells > 6 groups, however, the upper limits of the confidence interval around the post-test probability for PE were 16% and 33%, respectively, for these high probability groups. In this pilot study, the rapid ELISA D-dimer had high sensitivity and negative predictive value even when applied to patients with high pretest probability for PE. However, with the post-test probability of PE still as high as 16–33% in the negative D-dimer groups, this precludes applying the results to patient care at present. Further testing is warranted to determine whether these findings can be safely incorporated into practice.     

Utility of an Initial D-dimer Assay in Screening for Traumatic or Spontaneous Intracranial Hemorrhage

OBJECTIVE: To evaluate the sensitivity of a D-dimer assay as a screening tool for possible traumatic or spontaneous intracranial hemorrhage. If adequately sensitive, the D-dimer assay may potentially permit omission of a more expensive computed tomography (CT) scan of the head when such hemorrhage is clinically suspected. METHODS: Prospective, consecutive, blinded study of patients (age > 16 years) requiring a CT scan of the head for suspected intracranial hemorrhage over a five-month period at a university, Level I trauma center. All study patients had a serum D-dimer assay obtained prior to their CT scans. Sensitivity and specificity, with 95% confidence intervals (95% CIs), of the enzyme-linked immunosorbent assay (ELISA) D-dimer assay for the detection of intracranial hemorrhage were calculated. RESULTS: Of the 319 patients entered in the study, 25 (7.8%) had a CT scan positive for intracranial hemorrhage. Patients with intracranial hemorrhage were more likely to have a positive D-dimer assay (chi-square = 13.075, p < 0.001). The D-dimer assay had 21 true-positive and four false-negative tests, resulting in a sensitivity of 84.0% (95% CI = 63.7% to 95.5%) and a specificity of 55.8% (95% CI = 55.5% to 55.9%). The four false-negative cases included one small intraparenchymal hemorrhage, one small subarachnoid hemorrhage, one moderate-sized intraparenchymal hemorrhage with mid-line shift, and one large subdural hematoma requiring emergent surgery. CONCLUSIONS: Due to the catastrophic nature of missing an intracranial hemorrhage in the emergency department, the D-dimer assay is not adequately sensitive or predictive to use as a screening tool to allow routine omission of head CT scanning.     

Diagnostic accuracy of D-dimer test for exclusion of venous thromboembolism: a systematic review

Summary.  Background: The reported diagnostic accuracy of the D-dimer test for exclusion of deep vein thrombosis (DVT) and pulmonary embolism (PE) varies. It is unknown to what extent this is due to differences in study design or patient groups, or to genuine differences between D-dimer assays. Methods: Studies evaluating the diagnostic accuracy of the D-dimer test in the diagnosis of venous thromboembolism were systematically searched for in the MEDLINE and EMBASE databases up to March 2005. Reference lists of all included studies and of reviews related to the topic of the present meta-analysis were manually searched for other additional potentially eligible studies. Two reviewers independently extracted study characteristics using standardized forms. Results: In total, 217 D-dimer test evaluations for DVT and 111 for PE were analyzed. Several study design characteristics were associated with systematic differences in diagnostic accuracy. After adjustment for these features, the sensitivities of the D-dimer enzyme-linked immunofluorescence assay (ELFA) (DVT 96%; PE 97%), microplate enzyme-linked immunosorbent assay (ELISA) (DVT 94%; PE 95%), and latex quantitative assay (DVT 93%; PE 95%) were superior to those of the whole-blood D-dimer assay (DVT 83%; PE 87%), latex semiquantitative assay (DVT 85%; PE 88%) and latex qualitative assay (DVT 69%; PE 75%). The latex qualitative and whole-blood D-dimer assays had the highest specificities (DVT 99%, 71%; PE 99%, 69%). Conclusions: Compared to other D-dimer assays, the ELFA, microplate ELISA and latex quantitative assays have higher sensitivity but lower specificity, resulting in a more confident exclusion of the disease at the expense of more additional imaging testing. These conclusions are based on the most up-to-date and extensive systematic review of the topic area, including 184 articles, with 328 D-dimer test evaluations.     

D-dimer levels in VTE patients with distal and proximal clots

Objectives

There is growing evidence that venous thromboembolism (VTE) patients with distal clots (distal calf deep vein thrombosis [DVT] and sub-segmental pulmonary embolism [PE]) may not routinely benefit from anticoagulation. We compared the D-dimer levels in VTE patients with distal and proximal clots.

Tandem measurement of D-dimer and myeloperoxidase or C-reactive protein to effectively screen for pulmonary embolism in the emergency department

OBJECTIVES: The hypothesis was that the tandem measurement of D-dimer and myeloperoxidase (MPO) or C-reactive protein (CRP) could significantly decrease unnecessary pulmonary vascular imaging in emergency department (ED) patients evaluated for pulmonary embolism (PE) compared to D-dimer alone. METHODS: The authors measured the sequential combinations of D-dimer and MPO and D-dimer and CRP in a prospective sample of ED patients evaluated for PE at two centers. Patients were followed for 90 days for venous thromboembolism (VTE, either PE or deep venous thrombosis [DVT]), which required the consensus of two of three blinded physician reviewers. RESULTS: The authors enrolled 304 patients, 22 with VTE (7%; 95% confidence interval [CI] = 5% to 10%). The sensitivity and specificity of a D-dimer alone (cutoff > or = 500 ng/mL) were 100% (95% CI = 85% to 100%) and 59% (95% CI = 53% to 65%), respectively, and was followed by pulmonary vascular imaging negative for PE in 38% (115/304; 95% CI = 32% to 44%). The combination of either a negative D-dimer, or MPO < 22 mg/dL, had a sensitivity of 100% and specificity of 73% (95% CI = 67% to 78%). Thus, tandem measurement of D-dimer and MPO would have decreased the frequency of subsequent negative pulmonary vascular imaging from 38% to 25% (95% CI of the difference of -13% = -5% to -20%). The combination of CRP and D-dimer would not have significantly improved the rate of negative imaging. CONCLUSIONS: The tandem measurement of D-dimer and MPO would have significantly decreased negative pulmonary vascular imaging compared with D-dimer alone and should be validated prospectively.     

Capnometry in suspected pulmonary embolism with positive D-dimer in the field

Introduction  

Pulmonary embolism (PE) is one of the greatest diagnostic challenges in prehospital emergency setting. Most patients with suspected PE have a positive D-dimer and undergo diagnostic testing. Excluding PE with additional non-invasive tests would reduce the need for further imaging tests. We aimed to determine the effectiveness of combination of clinical probability and end-tidal carbon dioxide (PetCO₂) for evaluation of suspected PE with abnormal concentrations of D-dimer in prehospital emergency setting.     

Exclusion of pulmonary embolism using quantitative plasma D-dimer assays

Recent quantitative studies using pulmonary angiography as reference method have indicated that the overall accuracy of quantitative D-dimer assays for the exclusion of pulmonary embolism (PE) in patients suspected of PE is poorer than was reported in earlier studies in which the same D-dimer assays were used (90-94% vs 98-100%). An explanation can be found in the fact that the earlier studies are hampered by the fact that the reference method was a compilation of clinical data and non-invasive diagnostic tests rather than a true gold standard. Furthermore, in those studies no discrimination was made between the milder cases of subsegmental PE and the more severe cases of segmental and larger PE. The lack of a true gold standard and preselection leading to reduced proportions of cases of subsegmental PE in the earlier studies rather than differences in the storage conditions of plasma samples or treatment with heparin, appear to have caused the discrepancies in the reported accuracy of D-dimer assays. It is concluded that the sensitivity and negative predictive values obtained with different quantitative D-dimer assays are in close agreement with each other, that is poor for subsegmental PE and excellent for segmental and larger PE. In diagnostic algorithms D-dimer can reliably exclude acute segmental and/or massive PE. Further work-up within 48 hours is still necessary in negative D-dimer outcomes to exclude subsegmental PE.     

Pulmonary embolism despite negative ELISA D-dimer: a case report

Pulmonary embolus (PE) can be fatal, but is often treatable if recognized early. Unfortunately, the clinical presentation of PE is often variable and misleading. The D-dimer assay has recently come into favor as a method to exclude PE; however, this test has an acceptable safety margin only in low-risk populations. What is unclear is the exact composition of this low risk population. This is the report of a 26-year-old woman with over 2 weeks of chest pain and intermittent dyspnea. The patient was initially seen in the Emergency Department (ED) and hospitalized. She returned to the ED 2 weeks later with similar symptoms. Although enzyme-linked immunosorbent assay (ELISA) D-dimer assays were normal on the initial and subsequent ED visits, pulmonary embolism (PE) was diagnosed by computed tomography scan on the second visit. This report highlights the risk of misdiagnosing PE if relying solely on ELISA D-dimer for exclusion. The approach to PE should include a measure of clinical probability. This report documents the presentation of PE despite having two unremarkable ELISA D-dimer measurements, and highlights the importance of clinical suspicion.     

Clinical probability and alveolar dead space measurement for suspected pulmonary embolism in patients with an abnormal D-dimer test result

BACKGROUND: Most patients with suspected pulmonary embolism (PE) have a positive D-dimer test and undergo diagnostic imaging. Additional non-invasive bedside tests are required to reduce the need for further diagnostic tests. OBJECTIVES: We aimed to determine whether a combination of clinical probability assessment and alveolar dead space fraction measurement can confirm or exclude PE in patients with an abnormal D-dimer test. METHODS: We assessed clinical probability of PE and alveolar dead space fraction in 270 consecutive in- and outpatients with suspected PE and positive D-dimer. An alveolar dead space fraction < 0.15 was considered normal. PE was subsequently excluded or confirmed by venous compression ultrasonography, spiral computed tomography and a 3-month follow-up. Radiologists were unaware of the results of clinical probability and capnography. RESULTS: PE was confirmed in 108 patients (40%). Capnography had a sensitivity of 68.5% (95% confidence interval [CI]: 58.9-77.1%) and a specificity of 81.5% (95% CI: 74.6-87.1%) for PE. Forty-five patients (16.6%) had both a low clinical probability and normal capnography (sensitivity: 99.1%, 95% CI: 94.9-100%) and 34 patients (12.6%) had both a high clinical probability and abnormal capnography (specificity: 100%, 95% CI: 97.7-100%). CONCLUSION: Capnography alone does not exclude PE accurately. The combination of clinical probability and capnography accurately excludes or confirms PE and avoids further testing in up to 30% of patients.     

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

ObjectivesDetermine whether D-dimer concentration in the absence of imaging can differentiate patients that require anti-coagulation from patients who do not require anti-coagulation.MethodsData 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.ResultsThe ‘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%).ConclusionsAn 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.     

血浆D-二聚体在肺栓塞患者中的诊断意义

目的:探讨快速定量检测D-二聚体在诊断肺栓塞患者中的临床价值。方法:检测、分析21例经螺旋CT或肺动脉造影确诊的肺栓塞患者及19例健康人(对照组)的血浆D-二聚体含量。结果:与对照组比较,肺栓塞组D-二聚体含量明显升高,有显著性差异(P<0.01)。结论:肺栓塞患者D-二聚体含量明显升高,敏感性为100%,阴性预测值为100%,检测D-二聚体可作为诊断肺栓塞的首选筛选试验。