| Article Access Statistics | | | Viewed | 5791 | | | Printed | 265 | | | Emailed | 0 | | | PDF Downloaded | 20 | | | Comments | [Add] | | | Cited by others | 5 | | |
|
Click on image for details.
|
|
 |
| ORIGINAL ARTICLE |
|
|
|
| Year : 2018 | Volume
: 64
| Issue : 3 | Page : 150-154 |
Assessment of the current D-dimer cutoff point in pulmonary embolism workup at a single institution: Retrospective study
S Alhassan1, E Bihler1, K Patel2, S Lavudi2, M Young2, M Balaan1
1 Division of Pulmonary and Critical Care Medicine, Allegheny General Hospital, Pittsburgh, Pennsylvania, USA
2 Department of Medicine, Allegheny General Hospital, Pittsburgh, Pennsylvania, USA
| Date of Submission | 19-Apr-2017 |
| Date of Decision | 27-Sep-2017 |
| Date of Acceptance | 24-Sep-2017 |
| Date of Web Publication | 11-Jul-2018 |
Correspondence Address:
Dr. S Alhassan
Division of Pulmonary and Critical Care Medicine, Allegheny General Hospital, Pittsburgh, Pennsylvania
USA
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jpgm.JPGM_217_17
Background: The currently used D-dimer (DD) cutoff point is associated with a large number of negative CT-pulmonary angiographies (CTPA). We hypothesized presence of deficiency in the current cutoff and a need to look for a better DD threshold. Materials and Methods: We conducted a retrospective medical records analysis of all patients who had a CTPA as part of pulmonary embolism (PE) workup over a 1-year period. All emergency room (ER) patients who had DD assay checked prior to CTPA were included in the analysis. We assessed our institutional cutoff point and tried to test other presumptive DD thresholds retrospectively. Results: At our institution 1591 CTPA were performed in 2014, with 1220 scans (77%) performed in the ER. DD test was ordered prior to CTPA imaging in 238 ER patients (19.5%) as part of the PE workup. PE was diagnosed in 14 cases (6%). The sensitivity and specificity of the currently used DD cutoff (0.5 mcg/mL) were found to be 100% and 13%, respectively. Shifting the cutoff value from 0.5 to 0.85 mcg/mL would result in a significant increase in the specificity from 13% to 51% while maintaining the same sensitivity of 100%. This would make theoretically 84 CTPA scans, corresponding to 35% of CTPA imaging, unnecessary because DD would be considered negative based on this presumptive threshold. Conclusions: Our results suggest a significant deficiency in the institutional DD cutoff point with the need to find a better threshold through a large multicenter prospective trial to minimize unnecessary CTPA scans and to improve patient safety.
Keywords: CT-pulmonary angiography, D-dimer cutoff, pulmonary embolism
How to cite this article:
Alhassan S, Bihler E, Patel K, Lavudi S, Young M, Balaan M. Assessment of the current D-dimer cutoff point in pulmonary embolism workup at a single institution: Retrospective study. J Postgrad Med 2018;64:150-4 |
How to cite this URL:
Alhassan S, Bihler E, Patel K, Lavudi S, Young M, Balaan M. Assessment of the current D-dimer cutoff point in pulmonary embolism workup at a single institution: Retrospective study. J Postgrad Med [serial online] 2018 [cited 2023 May 31];64:150-4. Available from: https://www.jpgmonline.com/text.asp?2018/64/3/150/233735 |
| :: Background | |  |
Pulmonary embolism (PE) has an approximate incidence of 70 per 100000 every year, and mortality rate of 15% in the first 90 days post diagnosis.[1],[2],[3] It has a variety of nonspecific presentations which make the diagnosis challenging.[4] Computed tomographic pulmonary angiography (CTPA) has evolved as the new reference gold standard tool in evaluating patients with suspected PE.[3],[4],[5] However, the drawbacks of CTPA ought to be taken in consideration during PE workup such as radiation exposure, contract-induced nephropathy (CIN), and high cost.[6],[7] Therefore, evidence-based guidelines recommend using one of the validated score systems (Wells or Geneva criteria) to assess pretest probability (PTP) of PE and utilizing D-dimer (DD) testing in excluding PE for patients with low PTP.[8],[9],[10],[11]
DD is a degradation product from cross-linked fibrin due to plasmin-mediated fibrinolysis.[12] Enzyme-linked immunosorbent assay (ELISA) and latex-based automated immunoturbidimetric assay were found to be the most sensitive quantitative methods to measure the DD values.[13] The reference laboratory ranges of DD assay are either less than 0.5 mcg/mL Fibrinogen Equivalent Units (FEU) or less than 0.25 mcg/mL D-dimer Units (DDU).[14] PE was found to result in a significant increase in DD.[15] However, DD can also be elevated in other conditions with a high fibrin turnover such as aging, pregnancy, surgery, immobility, active malignancy, sickle cell disease, and inflammatory process; or with a decreased fibrin clearance as end-stage renal and liver diseases.[13],[16]
At our institution, we noticed that a high number of CTPA scans had been ordered because of a slight increase in DD values. The vast majority of these scans came back negative for PE. Thus, we performed a retrospective analysis on all patients with suspected PE who had both DD and CTPA to demonstrate the deficiencies of the currently used DD cutoff point at our institution.
| :: Materials and Methods | | |
Study design and data collection
We conducted a retrospective study at Allegheny General Hospital (AGH) during a 1-year period from January 1, 2014 through December 31, 2014. AGH is a tertiary care academic center in Pittsburgh, Pennsylvania, with more than 55,000 emergency room visits per year. The Institutional Review Board of AGH granted the permission for our study.
We obtained all cases of CTPA scans performed during the study time frame from a radiology registry. Thereafter, we extracted emergency room (ER) patients who had DD assay checked prior to CTPA as part of their PE workup. Our investigators retrospectively reviewed patient charts and collected relevant data including patient demographics (age, gender, and race), DD values, and CTPA results.
CTPA imaging was labeled as positive and negative for acute PE based on an independent interpretation by board-certified chest radiologists. DD measurements at AGH were reported in fibrinogen equivalent units as micrograms per milliliter (mcg/mL) using automated immunoturbidimetric method, with normal DD reference of <0.5 mcg/mL.
Outcome
The study was performed to retrospectively assess the sensitivity and specificity of the current institutional DD cutoff point and to compare its efficacy with other presumptive DD cutoff points. Thus, we tried to examine the sensitivity and specificity of different theoretical DD thresholds which are higher than 0.5 mcg/mL in a retrospective nature. The best DD threshold was defined as a DD value which maintains the same sensitivity of the current DD cutoff but the least false positive rate. In addition, the newly recommended age-adjusted DD cutoff point (age × 0.01 mcg/mL FEU)[17] was retrospectively applied on our sample to compare it with our institutional DD cutoff.
Statistical analyses
The Statistical Package for the Social Sciences (SPSS) version 18 was employed for statistical analyses. Chi-square test was applied in 2 × 2 contingency tables to explore the difference between the categorical variables such as gender, ethnicity, and CTPA results. An unpaired t-test was used to illustrate the associations among the continuous variables such as age and DD values. Receiver-Operator Characteristics (ROC) curve was used to locate the ideal DD cutoff value and to calculate the sensitivity and specificity for all possible threshold points of DD assay. The statistical significance was determined when P values were less than 0.05.
| :: Results | | |
Radiology registry provided 1591 consecutive CTPA cases performed at AGH during the study period; out of which, 1220 scans were ordered in the emergency room (ER). We identified 238 ER patients (19.5%) who had DD test checked prior to CTPA scan as part of their PE workup [Figure 1]. This sample had 148 females (62%) and 158 Caucasians (66%), with an average age of 53 years (18–93 years) [Figure 2]. | Figure 1: Study flowchart. CTPA: computed tomographic pulmonary angiography; DD: D-dimer; ER: emergency room; PE: pulmonary embolism
Click here to view |
PE was diagnosed in 14 cases (6%). Chest pain and dyspnea were the leading complaints for PE workup [Table 1]. DD value was significantly higher among patients with diagnosed PE compared to those who did not have PE; 6.1 mcg/mL versus 1.5 mcg/mL, respectively (P< 0.0001) [Figure 3]. As shown in [Figure 3], the majority of false positive DD values were found in the range of 0.51–2.00 mcg/mL. | Figure 3: Distribution of D-dimer values in patients with and without pulmonary embolism. DD: D-dimer; PE: pulmonary embolism
Click here to view |
The sensitivity and specificity of the currently used DD cutoff value (0.5 mcg/mL) in our sample were found to be 100% and 13%, respectively. ROC curve was performed for all possible DD cutoff levels with area under the curve of 0.86 (95% confidence interval of 0.77–0.94) [Figure 4]. The analysis suggested multiple cutoff points with different sensitivity and specificity rates as demonstrated in [Table 2]. | Figure 4: Receiver-Operator Characteristics (ROC) curve for all possible D-dimer cutoff points
Click here to view |
 | Table 2: Suggested D-dimer cutoff points with their sensitivities, specificities, positive and negative predictive values, and false positive rates
Click here to view |
Our study revealed that shifting the cutoff value of DD test from 0.5 mcg/mL to 0.85 mcg/mL would result in a significant increase in the specificity from 13% to 51% while maintaining the same sensitivity of 100% and the same negative predictive value (NPV) of 100%. In addition, it was noted that 82% of DD results in our sample were found to be false positive based on the currently used DD cutoff. This percentage would decrease to 46% if the shifted cutoff (0.85 mcg/mL) had been used.
If we assume that we had applied the increased threshold of 0.85 mcg/mL on our sample, this would change the interpretation of 84 D-dimer cases from being “positive” to be “negative” without missing PE. This would presumptively make 84 CTPA scans, corresponding to 35% of all CTPA imaging, unnecessary since DD would be negative based on the shifted cutoff.
On the other hand, we found that applying the validated age-adjusted cutoff point of DD assay on our sample could safely have saved 12 CTPA scans, corresponding to 5% of all CTPA imaging, without missing any single PE case.
| :: Discussion | | |
The need for a new DD threshold in PE workup
Our study revealed that a significant number of negative CTPA scans are performed due to a slight increase in DD value above the traditional cutoff (0.5 mcg/mL). These scans could be avoidable if the cutoff was higher. ROC curve demonstrated a correlation between rising DD cutoff point and a substantial increase in the specificity of this test. Simultaneously, the test's sensitivity had not changed until the cutoff exceeded the value of 0.85 mcg/mL, as shown in [Table 2].
Shifting the DD cutoff value from 0.5 mcg/mL to 0.85 mcg/mL not only resulted in almost 4-fold improvement in the test's specificity but it also maintained an optimal sensitivity of 100%. Thus, more than a third of CTPA scans would be presumptively considered unnecessary by applying the shifted threshold of 0.85 mcg/mL. Moreover, the ADJUST-PE study, which is a multicenter multinational prospective trial, had already validated the use of age-adjusted cutoff for DD assay instead of a fixed threshold.[17] Therefore, age adjustment is necessary for any DD cutoff that will be used for PE workup.
There are similar studies that shed light on the importance of moving the DD cutoff point up to a higher level where unnecessary CTPA examinations can be minimized without changing the crucial role of DD in ruling out PE.[18],[19] However, all of these studies are retrospective reviews with no consensus on a certain fixed value and not taking into consideration the aging factor. Thus, prospective trials are needed to validate using a shifted DD cutoff combined with age adjustment. Such practice will have a momentous impact on patient safety and hospital resources utilization.
Hospital resources overutilization
CTPA imaging is over-utilized and has exponentially increased over the past two decades with decreasing positivity rate.[20],[21],[22],[23] Physicians' noncompliance with evidence-based guidelines was found to be a major contributing factor to CTPA overuse nationwide.[24],[25],[26],[27],[28],[29],[30],[31],[32],[33] In our study, less than 20% of ER patients with suspected PE underwent DD testing prior to CTPA scan. In addition, we found 30 cases (12.6%) where physician proceeded to CTPA despite negative DD. There are several presumptive reasons behind such high noncompliance, which include insufficient training on calculating PTP score, fear of malpractice litigation, or performing additional thoracic imaging to look for an alternative diagnosis.[34],[35]
On the other hand, DD testing might lead to ordering unnecessary CTPA scans due to its high false positive rate.[36] This has raised the suspicion about the efficacy of the currently used DD cutoff point and the necessity to raise it to a better practical threshold.[37],[38],[39] In our study, the false positive rate of DD assay decreased by applying retrospectively the age-adjusted DD cutoff on our sample and by making a theoretical threshold of 0.85 mcg/mL.
We believe that improving physicians' compliance in practicing the evidence-based diagnostic algorithms along with adjusting the DD cutoff point in PE workup would avert performing a lot of unnecessary CTPA imaging. Such changes can aid in reducing patients' exposure to the disadvantages of this radiologic modality, which include radiation-related cancer risk, CIN, contrast-induced anaphylactic reactions, pulmonary edema, cardiac arrhythmias, and contrast-related death.[40],[41],[42]
Study limitations
The limitations of our study include the retrospective nature of the analysis and conducting the study at a single medical center. In addition, the study examined DD cutoff points by reviewing CTPA registry without taking into account those who underwent perfusion/ventilation examinations or those who had DD testing and no subsequent imaging during PE workup. Moreover, the study revealed that DD testing was ordered in only 20% of CTPA cases without knowing the reasons behind selecting these cases by ER physicians, which makes us unable to rule out a selection bias in our sample. Thus, it will be difficult to examine the safety and the validation of a new DD cutoff based on the methodology applied in this study. However, our review highlights the deficit in the currently used DD cutoff and the possibility of considering a shifted DD threshold in addition to age adjustment in future trials.
| :: Conclusion | | |
Our data shows a significant deficiency in the currently used DD cutoff point. Applying the age adjusted DD cutoff and testing the safety of a shifted threshold through a large multicenter prospective trial would help in reducing the amount of unnecessary CTPA scans. Such practice can potentially improve patient safety and hospital resources utilization.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| :: References | | |
| 1. | Silverstein MD, Heit JA, Mohr DN, Petterson TM, O'Fallon WM, Melton LJ 3 rd. Trends in the incidence of deep vein thrombosis and pulmonary embolism: A 25-year population-based study. Arch Intern Med 1998;158:585-93.  |
| 2. | Goldhaber SZ, Visani L, De Rosa M. Acute pulmonary embolism: Clinical outcomes in the International Cooperative Pulmonary Embolism Registry (ICOPER). Lancet 1999;353:1386-9. |
| 3. | Piazza G, Goldhaber SZ. Acute pulmonary embolism: Part I: Epidemiology and diagnosis. Circulation 2006;114:e28-32. |
| 4. | Morris TA, Fedullo PF. Pulmonary Thromboembolism. In: Broaddus CV, Mason RJ, Ernst JD, King TE Jr, Lazarus SC, Murray JF, et al, editors. Murray & Nadel's Textbook of Respiratory Medicine. 6 th ed. Philadelphia, PA: Elsevier Saunders; 2015. pp 1001-30. |
| 5. | Agnelli G, Becattini C. Acute pulmonary embolism. N Engl J Med 2010;363:266-74. |
| 6. | Brenner DJ, Hall EJ. Computed tomography--an increasing source of radiation exposure. N Engl J Med 2007;357:2277-84. |
| 7. | Mitchell AM, Jones AE, Tumlin JA, Kline JA. Prospective study of the incidence of contrast-induced nephropathy among patients evaluated for pulmonary embolism by contrast-enhanced computed tomography. Acad Emerg Med 2012;19:618-25. |
| 8. | Wells PS, Ginsberg JS, Anderson DR, Kearon C, Gent M, Turpie AG, et al. Use of a clinical model for safe management of patients with suspected pulmonary embolism. Ann Intern Med 1998;129:997-1005. |
| 9. | Wells PS, Anderson DR, Rodger M, Stiell I, Dreyer JF, Barnes D, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: Management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Ann Intern Med 2001;135:98-107. |
| 10. | Wells PS, Anderson DR, Rodger M, Ginsberg JS, Kearon C, Gent M, et al. Derivation of a simple clinical model to categorize patients probability of pulmonary embolism: Increasing the models utility with the SimpliRED D-dimer. Thromb Haemost 2000;83:416-20. |
| 11. | Le Gal G, Righini M, Roy PM, Sanchez O, Aujesky D, Bounameaux H, et al. Prediction of pulmonary embolism in the emergency department: the revised Geneva score. Ann Intern Med 2006;144:165-71. |
| 12. | Adam SS, Key NS, Greenberg CS. D-dimer antigen: Current concepts and future prospects. Blood 2009;113:2878-87. |
| 13. | Tripodi A. D-dimer testing in laboratory practice. Clin Chem 2011;57:1256-62. |
| 14. | |
| 15. | Bounameaux H, Cirafici P, de Moerloose P, Schneider PA, Slosman D, Reber G, et al. Measurement of D-dimer in plasma as diagnostic aid in suspected pulmonary embolism. Lancet 1991;337:196-200. |
| 16. | Kabrhel C, Mark Courtney D, Camargo CA Jr, Plewa MC, Nordenholz KE, Moore CL, et al. Factors associated with positive D-dimer results in patients evaluated for pulmonary embolism. Acad Emerg Med 2010;17:589-97. |
| 17. | Righini M, Van Es J, Den Exter PL, Roy PM, Verschuren F, Ghuysen A, et al. Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: The ADJUST-PE study. JAMA 2014;311:1117-24. |
| 18. | Raviv B, Israelit SH. Shifting up cutoff value of d-dimer in the evaluation of pulmonary embolism: A viable option? Possible risks and benefits. Emerg Med Int 2012;2012:517375. |
| 19. | Vossen JA, Albrektson J, Sensarma A, Williams SC. Clinical usefulness of adjusted D-dimer cut-off values to exclude pulmonary embolism in a community hospital emergency department patient population. Acta Radiol. 2012;53:765-8. |
| 20. | Prologo JD, Gilkeson RC, Diaz M, Asaad J. CT pulmonary angiography: A comparative analysis of the utilization patterns in emergency department and hospitalized patients between 1998 and 2003. AJR Am J Roentgenol 2004;183:1093-6. |
| 21. | Weir ID, Drescher F, Cousin D, Fraser ET, Lee R, Berman L, et al. Trends in use and yield of chest computed tomography with angiography for diagnosis of pulmonary embolism in a Connecticut hospital emergency department. Conn Med 2010;74:5-9. |
| 22. | Donohoo JH, Mayo-Smith WW, Pezzullo JA, Egglin TK. Utilization patterns and diagnostic yield of 3421 consecutive multidetector row computed tomography pulmonary angiograms in a busy emergency department. J Comput Assist Tomogr 2008;32:421-5. |
| 23. | David S, Beddy P, Babar J, Devaraj A. Evolution of CT pulmonary angiography: Referral patterns and diagnostic yield in 2009 compared with 2006. Acta Radiol 2012;53:39-43. |
| 24. | Costantino MM, Randall G, Gosselin M, Brandt M, Spinning K, Vegas CD. CT angiography in the evaluation of acute pulmonary embolus. AJR Am J Roentgenol 2008;191:471-4. |
| 25. | Teismann NA, Cheung PT, Frazee B. Is the ordering of imaging for suspected venous thromboembolism consistent with D-dimer result? Ann Emerg Med 2009;54:442-6. |
| 26. | Corwin MT, Donohoo JH, Partridge R, Egglin TK, Mayo-Smith WW. Do emergency physicians use serum D-dimer effectively to determine the need for CT when evaluating patients for pulmonary embolism? Review of 5,344 consecutive patients. AJR Am J Roentgenol 2009;192:1319-23. |
| 27. | Crichlow A, Cuker A, Mills AM. Overuse of computed tomography pulmonary angiography in the evaluation of patients with suspected pulmonary embolism in the emergency department. Acad Emerg Med 2012;19:1219-26. |
| 28. | Yin F, Wilson T, Della Fave A, Larsen M, Yoon J, Nugusie B, et al. Inappropriate use of D-dimer assay and pulmonary CT angiography in the evaluation of suspected acute pulmonary embolism. Am J Med Qual. 2012;27:74-9. |
| 29. | Venkatesh AK, Kline JA, Courtney DM, Camargo CA, Plewa MC, Nordenholz KE, et al. Evaluation of pulmonary embolism in the emergency department and consistency with a national quality measure: Quantifying the opportunity for improvement. Arch Intern Med 2012;172:1028-32. |
| 30. | Adams DM, Stevens SM, Woller SC, Evans RS, Lloyd JF, Snow GL, et al. Adherence to PIOPED II investigators' recommendations for computed tomography pulmonary angiography. Am J Med 2013;126:36-42. |
| 31. | Shujaat A, Shapiro JM, Eden E. Utilization of CT Pulmonary Angiography in Suspected Pulmonary Embolism in a Major Urban Emergency Department. Pulm Med 2013;2013:915213. |
| 32. | Perelas A, Dimou A, Saenz A, Rhee JH, Teerapuncharoen K, Rowden A, et al. CT Pulmonary Angiography Utilization in the Emergency Department: Diagnostic Yield and Adherence to Current Guidelines. Am J Med Qual 2015;30:571-7. |
| 33. | Alhassan S, Sayf AA, Arsene C, Krayem H. Suboptimal implementation of diagnostic algorithms and overuse of computed tomography-pulmonary angiography in patients with suspected pulmonary embolism. Ann Thorac Med 2016;11:254-60. [ PUBMED] [Full text] |
| 34. | Rohacek M, Buatsi J, Szucs-Farkas Z, Kleim B, Zimmermann H, Exadaktylos A, et al. Ordering CT pulmonary angiography to exclude pulmonary embolism: defense versus evidence in the emergency room. Intensive Care Med 2012;38:1345-51. |
| 35. | Raja AS, Greenberg JO, Qaseem A, Denberg TD, Fitterman N, Schuur JD, et al. Evaluation of Patients With Suspected Acute Pulmonary Embolism: Best Practice Advice From the Clinical Guidelines Committee of the American College of Physicians. Ann Intern Med 2015;163:701-11. |
| 36. | Kabrhel C, Matts C, McNamara M, Katz J, Ptak T. A highly sensitive ELISA D-dimer increases testing but not diagnosis of pulmonary embolism. Acad Emerg Med 2006;13:519-24. |
| 37. | Righini M, Aujesky D, Roy PM, Cornuz J, de Moerloose P, Bounameaux H, et al. Clinical usefulness of D-dimer depending on clinical probability and cutoff value in outpatients with suspected pulmonary embolism. Arch Intern Med 2004;164:2483-7. |
| 38. | Douma RA, le Gal G, Söhne M, Righini M, Kamphuisen PW, Perrier A, et al. Potential of an age adjusted D-dimer cut-off value to improve the exclusion of pulmonary embolism in older patients: a retrospective analysis of three large cohorts. BMJ 2010;340:c1475. |
| 39. | Schouten HJ, Geersing GJ, Koek HL, Zuithoff NP, Janssen KJ, Douma RA, et al. Diagnostic accuracy of conventional or age adjusted D-dimer cut-off values in older patients with suspected venous thromboembolism: Systematic review and meta-analysis. BMJ 2013;346:f2492. |
| 40. | Brenner DJ, Elliston CD. Estimated radiation risks potentially associated with full-body CT screening. Radiology 2004;232:735-8. |
| 41. | Singh J, Daftary A. Iodinated contrast media and their adverse reactions. J Nucl Med Technol 2008;36:69-74; quiz 76-7. |
| 42. | Cochran ST. Anaphylactoid reactions to radiocontrast media. Curr Allergy Asthma Rep 2005;5:28-31. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]
| This article has been cited by | | 1 |
Characterizing and quantifying low-value diagnostic imaging internationally: a scoping review |
|
| Elin Kjelle, Eivind Richter Andersen, Arne Magnus Krokeide, Lesley J. J. Soril, Leti van Bodegom-Vos, Fiona M. Clement, Bjørn Morten Hofmann | | BMC Medical Imaging. 2022; 22(1) | | [Pubmed] | [DOI] | | | 2 |
Elderly Population with COVID-19 and the Accuracy of Clinical Scales and D-Dimer for Pulmonary Embolism: The OCTA-COVID Study |
|
| Maribel Quezada-Feijoo, Mónica Ramos, Isabel Lozano-Montoya, Mónica Sarró, Verónica Cabo Muiños, Rocío Ayala, Francisco J. Gómez-Pavón, Rocío Toro | | Journal of Clinical Medicine. 2021; 10(22): 5433 | | [Pubmed] | [DOI] | | | 3 |
Retrospective analysis of the incidence of pulmonary embolism in CT images in patients with a positive value of D-dimers |
|
| Vlastimil Válek, Vlastimil Válek, Michal Uher | | Vnitrní lékarství. 2021; 67(5): e13 | | [Pubmed] | [DOI] | | | 4 |
Effectiveness of Clinical Decision Tools in Predicting Pulmonary Embolism |
|
| Michael A. Simon, Christopher Tan, Patrick Hilden, Lyle Gesner, Barry Julius, Yongchun Shen | | Pulmonary Medicine. 2021; 2021: 1 | | [Pubmed] | [DOI] | | | 5 |
Elevated D-Dimers and Right Ventricular Dysfunction on Echocardiography for Diagnosis of Pulmonary Embolism: A Validation Study |
|
| Hamid Sharif Khan , Asim Javed, Muhammad Mohsin, Shabana Kousar, Summaya Salik Malik, Jahanzeb Malik | | Cureus. 2020; | | [Pubmed] | [DOI] | |
|
|
|
|
|
|
|
|
