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

Importance of risk factors for the evaluation of patients with a suspected pulmonary embolism

The reliable exclusion of a pulmonary embolism (PE) in hemodynamically stable patients remains a challenge. The European Society of Cardiology guidelines for PE diagnosis published in 2008 and updated in 2014 recommend a low-threshold computed tomography (CT) indication for patients with a high probability of pulmonary embolism or those with elevated levels of D-dimers. Certain elements of the recommendations are controversial, while others, including the evaluation of the risk factors for PE, are considered only in individual cases. In the present study, various risk factors, including obesity, smoking, contraceptive use, immobility level, history of malignant disease and thrombophilia and the factors of familial predisposition, deep vein thrombosis (DVT)/PE-history, long-distance flying <1 week and surgery <4 weeks previously, were retrospectively examined in 492 patients with a suspected PE. The data demonstrated a significant risk of PE with contraceptive use, a history of DVT/PE and thrombophilia. The immobility level, surgery <4 weeks and long-distance flying <1 week previously, as well as family history, malignant disease, obesity and smoking, were not observed to be associated with a significantly higher risk of PE. Contraceptive use and thrombophilia, in addition to a history of DVT/PE, each appear to have a significant predictive value in the context of PE risk stratification. Therefore, patients with a suspected PE, who additionally present with at least one of the aforementioned risk factors, should undergo further diagnostic steps for PE risk stratification, including a low-threshold CT examination, even in the absence of elevated D-dimers.

Misinterpreting risk and test results delays diagnosis in a patient with pulmonary embolism

We report the case of a middle-aged man where a diagnosis of pulmonary embolism (PE) was delayed due to initial underestimation of risk and over-reliance on D-dimer testing. The patient presented with pleuritic chest pain after a 5 h domestic flight. The treating clinicians presumed that this duration of immobilisation was insufficient to cause a PE, D-dimer was not measured and the patient was discharged home. One week later, the patient re-presented due to persistence of chest pain. On this occasion, D-dimer was measured and it was normal, which was interpreted as excluding a PE. Subsequently, a CT pulmonary angiogram was performed, which demonstrated a subsegmental PE. This case highlights the importance of accurate assessment of PE-risk factors and following clinical guidelines, since a delayed diagnosis of PE is associated with increased mortality.

Computed tomographic pulmonary angiography and pulmonary embolism: predictive value of a d-dimer assay

Background

Computed tomographic pulmonary angiography (CTPA) is increasingly being used as first investigation for suspected pulmonary embolism (PE). The investigation has high predictive value, but is resource and time intensive and exposes patients to considerable radiation. Our aim was to assess the potential value of a negative d-dimer assay to exclude pulmonary emboli and reduce the number of performed CTPAs.

Methods

All CTPAs performed in a Scottish secondary care hospital for a fourteen month period were retrospectively reviewed. Collected data included the presence or absence of PE, d-dimer results and patient demographics. PE positive CTPAs were reviewed by a specialist panel.

Results

Pulmonary embolisms were reported for 66/405 (16.3%) CTPAs and d-dimer tests were performed for 216 (53%). 186/216 (86%) patients had a positive and 30 (14%) a negative d-dimer result. The panel agreed 5/66 (7.6%) false positive examinations. The d-dimer assay's negative predictive value was 93.3% (95% CI = 76.5%-98.8%) based on the original number of positive CTPAs and 100% (95% CI = 85.9%-100%) based on expert review. Significant non-PE intrapulmonary pathology was reported for 312/405 (77.0) CTPAs, including 13 new diagnoses of carcinoma.

Conclusions

We found that a low d-dimer score excluded all pulmonary embolisms, after a further specialist panel review identified initial false positive reports. However, current evidence-based guidelines still recommend that clinicians combine a d-dimer result with a validated clinical risk score when selecting suitable patients for CTPA. This may result in better use of limited resources, prevent patients being exposed to unnecessary irradiation and prevent potential complications as a result of iodinated contrast.

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.

Volumetric capnography: in the diagnostic work-up of chronic thromboembolic disease

The morbidity and mortality of pulmonary embolism (PE) have been found to be related to early diagnosis and appropriate treatment. The examinations used to diagnose PE are expensive and not always easily accessible. These options include noninvasive examinations, such as clinical pretests, ELISA D-dimer (DD) tests, and volumetric capnography (VCap). We report the case of a patient whose diagnosis of PE was made via pulmonary arteriography. The clinical pretest revealed a moderate probability of the patient having PE, and the DD result was negative; however, the VCap associated with arterial blood gases result was positive. The patient underwent all noninvasive exams following admission to hospital and again eight months after discharge. Results gained from invasive tests were similar to those produced by image exams, highlighting the importance of VCap as an important noninvasive tool.