DVT and Pulmonary Embolism: Part I. Diagnosis



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Am Fam Physician. 2004 Jun 15;69(12):2829-2836.

  This is part I of a two-part article on DVT and PE. Part II, “Treatment and Prevention,” appears in this issue on page 2841.

The online version of this article contains two tables that summarize risk-stratified performance of tests in DVT and PE.

The incidence of venous thromboembolic diseases is increasing as the U.S. population ages. At least one established risk factor is present in approximately 75 percent of patients who develop these diseases. Hospitalized patients and nursing home residents account for one half of all cases of deep venous thrombosis. A well-validated clinical prediction rule can be used for risk stratification of patients with suspected deep venous thrombosis. Used in combination with d-dimer or Doppler ultrasound tests, the prediction rule can reduce the need for contrast venography, as well as the likelihood of false-positive or false-negative test results. The inclusion of helical computed tomographic venography (i.e., a below-the-pelvis component) in pulmonary embolism protocols remains under evaluation. Specific combinations of a clinical prediction rule, ventilation-perfusion scanning, and d-dimer testing can rule out pulmonary embolism without an invasive or expensive investigation. A clinical prediction rule for pulmonary embolism is most helpful when it is used with subsequent evaluations such as ventilation-perfusion scanning, d-dimer testing, or computed tomography. Technologic advances are improving the resolution of helical computed tomography to allow detection of smaller emboli; however, further study is needed to provide definitive evidence supporting the role of this imaging technique in the diagnosis of pulmonary embolism. d-dimer testing is helpful clinically only when the result is negative. A negative d-dimer test can be used in combination with a clinical decision rule, ventilation-perfusion scanning, and/or helical computed tomography to lower the probability of pulmonary embolism to the point that aggressive treatment is not required. Evidence-based algorithms help guide the diagnosis of deep venous thrombosis and pulmonary embolism.

Venous thromboembolic disease represents a spectrum of conditions that includes deep venous thrombosis (DVT) and pulmonary embolism (PE). The estimated annual incidence of venous thromboembolism is 117 cases per 100,000 persons. The incidence rises markedly in persons 60 years and older and may be as high as 900 cases per 100,000 by the age of 85 years.1

Most clinically important PEs originate from proximal DVT of the leg (popliteal, femoral, or iliac veins).2 Upper extremity DVT is less common but also may lead to PE, especially in the presence of a venous catheter. A much less common cause of upper extremity DVT is Paget-Schroetter syndrome (idiopathic upper extremity DVT in young athletes).3

As the U.S. population ages, the medical and economic impact of venous thromboembolic disease is expected to increase. Part I of this two-part article reviews the diagnosis of DVT and PE. Part II4 reviews treatment and prevention.

Risk Factors for Venous Thromboembolism

Risk factors for venous thromboembolic disease include increasing age, prolonged immobility, surgery, trauma, malignancy, pregnancy, estrogenic medications (e.g., oral contraceptive pills, hormone therapy, tamoxifen [Nolvadex]), congestive heart failure, hyperhomocystinemia, diseases that alter blood viscosity (e.g., polycythemia, sickle cell disease, multiple myeloma), and inherited thrombophilias.

About 75 percent of patients with venous thromboembolic disease have at least one established risk factor, and one half of all cases of DVT occur in hospitalized patients or nursing home residents.5 Inherited thrombophilias can be identified in 24 to 37 percent of patients with DVT and in the majority of patients with familial thrombosis6,7  (Table 1).

TABLE 1

Thrombophilias Identified in Patients Presenting with DVT or PE

Anticoagulant protein deficiency

Protein S

Protein C

Antithrombin

Plasminogen

Heparin cofactor II

Dysfibrinogenemia

Combination deficiencies

Antiphospholipid antibodies

Factor V Leiden mutation (heterozygous)

Prothrombin G20210A mutation (heterozygous)7


DVT = deep venous thrombosis; PE = pulmonary embolism.

TABLE 1   Thrombophilias Identified in Patients Presenting with DVT or PE

View Table

TABLE 1

Thrombophilias Identified in Patients Presenting with DVT or PE

Anticoagulant protein deficiency

Protein S

Protein C

Antithrombin

Plasminogen

Heparin cofactor II

Dysfibrinogenemia

Combination deficiencies

Antiphospholipid antibodies

Factor V Leiden mutation (heterozygous)

Prothrombin G20210A mutation (heterozygous)7


DVT = deep venous thrombosis; PE = pulmonary embolism.

Diagnosis of DVT

When considered alone, the individual clinical features of DVT and PE have low predictive value (about 15 percent).8 Classic symptoms of DVT include swelling, pain, and discoloration in the affected extremity. Physical examination may reveal the palpable cord of a thrombosed vein, unilateral edema, warmth, and superficial venous dilation.9 Classic signs of DVT, including Homans sign (pain on passive dorsiflexion of the foot), edema, tenderness, and warmth, are difficult to ignore, but they are of low predictive value and can occur in other conditions such as musculoskeletal injury, cellulitis, and venous insufficiency. However, combinations of clinical features in the form of clinical prediction rules can be useful for stratifying patients into risk categories.

An algorithm developed by the Institute for Clinical Systems Improvement (ICSI), an independent nonprofit collaboration of health care providers and insurance companies, incorporates evidence-based recommendations for the use of pretest clinical probability with prediction rules, d-dimer testing, and imaging in the diagnosis of DVT (Figure 1).10

Deep Venous Thrombosis

FIGURE 1.

Diagnosis of deep venous thrombosis (DVT).

Adapted with permission from Institute for Clinical Systems Improvement. Healthcare guidelines. Venous thromboembolism. Accessed online February 6, 2004, at: http://www.icsi.org/knowledge/detail.asp?catID=29&itemID=202.

View Large

Deep Venous Thrombosis


FIGURE 1.

Diagnosis of deep venous thrombosis (DVT).

Adapted with permission from Institute for Clinical Systems Improvement. Healthcare guidelines. Venous thromboembolism. Accessed online February 6, 2004, at: http://www.icsi.org/knowledge/detail.asp?catID=29&itemID=202.

Deep Venous Thrombosis


FIGURE 1.

Diagnosis of deep venous thrombosis (DVT).

Adapted with permission from Institute for Clinical Systems Improvement. Healthcare guidelines. Venous thromboembolism. Accessed online February 6, 2004, at: http://www.icsi.org/knowledge/detail.asp?catID=29&itemID=202.

CLINICAL PREDICTION RULE

A well-validated clinical prediction rule provides a reliable estimate of the pretest probability of DVT (Table 2),8 which should, in turn, guide the interpretation of subsequent diagnostic tests. The value of various diagnostic tests and imaging studies in predicting the presence of DVT depends on the likelihood of disease in each risk group.8,1114 For example, the same test may rule out disease when it is negative in a low-probability patient but not when it is negative in a high-probability patient. Because many patients have an intermediate probability of venous thromboembolism, clinical judgment continues to be an important factor in making the decision to treat.

TABLE 2

Wells Clinical Prediction Rule for DVT

Clinical feature Points

Active cancer (treatment within 6 months, or palliation)

1

Paralysis, paresis, or immobilization of lower extremity

1

Bedridden for more than 3 days because of surgery (within 4 weeks)

1

Localized tenderness along distribution of deep veins

1

Entire leg swollen

1

Unilateral calf swelling of greater than 3 cm (below tibial tuberosity)

1

Unilateral pitting edema

1

Collateral superficial veins

1

Alternative diagnosis as likely as or more likely than DVT

−2

Total points:


DVT = deep venous thrombosis.

Risk score interpretation (probability of DVT): 3 points: high risk (75%); 1 to 2 points: moderate risk (17%);<1 point: low risk (3%).

Adapted with permission from Wells PS, Anderson DR, Bormanis J, Guy F, Mitchell M, Gray L, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet 1997;350:1796.

TABLE 2   Wells Clinical Prediction Rule for DVT

View Table

TABLE 2

Wells Clinical Prediction Rule for DVT

Clinical feature Points

Active cancer (treatment within 6 months, or palliation)

1

Paralysis, paresis, or immobilization of lower extremity

1

Bedridden for more than 3 days because of surgery (within 4 weeks)

1

Localized tenderness along distribution of deep veins

1

Entire leg swollen

1

Unilateral calf swelling of greater than 3 cm (below tibial tuberosity)

1

Unilateral pitting edema

1

Collateral superficial veins

1

Alternative diagnosis as likely as or more likely than DVT

−2

Total points:


DVT = deep venous thrombosis.

Risk score interpretation (probability of DVT): 3 points: high risk (75%); 1 to 2 points: moderate risk (17%);<1 point: low risk (3%).

Adapted with permission from Wells PS, Anderson DR, Bormanis J, Guy F, Mitchell M, Gray L, et al. Value of assessment of pretest probability of deep-vein thrombosis in clinical management. Lancet 1997;350:1796.

d-DIMER TESTS

Available d-dimer tests vary widely in sensitivity and specificity. Therefore, caution must be exercised in interpreting the results of these tests.15 However, one recent study16 found that the combination of a low-risk assessment by a validated clinical prediction rule and a negative second-generation latex agglutination d-dimer assay effectively rules out DVT. In another recent study,14 patients with a Wells clinical prediction rule score of less than 2 points and a negative d-dimer test were less likely to have venous thromboembolism during follow-up than were patients with a negative ultrasound examination (0.4 percent versus 1.4 percent). Note that a positive d-dimer assay does not raise the likelihood of DVT appreciably and therefore has limited clinical value.

DOPPLER ULTRASONOGRAPHY

Doppler ultrasonography is the most widely used modality for evaluating patients with suspected DVT. When used in combination with a clinical prediction rule, ultrasound examination is accurate in predicting the need for anticoagulation. However, a normal ultrasound study in a high-probability patient requires additional investigation before DVT can be ruled out.

Ultrasound assessment has several limitations: its accuracy depends on the operator; it cannot distinguish between an old clot and a new clot; and it is not accurate in detecting DVT in the pelvis or the small vessels of the calf, or in detecting DVT in the presence of obesity or significant edema. Causes of false-positive examinations include superficial phlebitis, popliteal cysts, and abscess.

HELICAL COMPUTED TOMOGRAPHY

With the advent of helical (spiral) computed tomographic (CT) scanning, protocols have emerged that combine CT pulmonary angiography with simultaneous below-the-pelvis CT venography. These “PE protocols” make it convenient to examine the chest and lower extremities simultaneously, without added contrast medium. One of the secondary objectives of the Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II)12 is to evaluate the diagnostic accuracy of helical CT scanning in patients with DVT.

Helical CT scanning of the legs costs about 50 percent more than compression ultrasonography. In addition, the risk of adverse reactions to contrast agents must be weighed. Currently, insufficient evidence supports the use of CT venography over Doppler ultrasonography for the diagnosis of lower extremity DVT.11

CONTRAST VENOGRAPHY

Although contrast venography is not performed often, it remains the gold standard against which noninvasive studies for DVT are compared. The use of contrast venography is limited by the risk of pain, phlebitis, and hypersensitivity or toxic reactions to contrast agents. Furthermore, DVT develops in a small number of patients who undergo the procedure. Conditions such as edema or obesity, which impair venous access, may make the test difficult or impossible to perform in approximately 10 percent of patients.17

IMPEDANCE PLETHYSMOGRAPHY

Impedance plethysmography (IPG) is a noninvasive and highly portable modality that has proved useful in the evaluation of patients with suspected DVT. Serial IPG is less sensitive than previously thought, and it may not detect proximal DVT.18 Failure to detect this condition is important, because proximal thrombi pose the greatest risk of embolization. Although IPG is popular in some countries, it is highly operator-dependent and relatively unavailable in the United States.

EMERGING TECHNOLOGIES

Magnetic resonance imaging (MRI) appears to be at least as sensitive as ultrasonography in detecting calf and pelvic DVTs.13 These thromboses are difficult to compress with ultrasonography and difficult to visualize with venography. However, MRI is highly operator-dependent, relatively unavailable, and generally more than twice as expensive as ultrasound examination.

Diagnosis of PE

The assessment for PE begins with a careful clinical examination and a determination of risk factors. The chest radiograph, arterial blood gas measurements, and electrocardiogram (ECG) also can be used to establish a high, intermediate, or low risk of PE.10

The ICSI algorithm for the diagnosis of PE is presented in Figure 2.10 This algorithm, like the one for DVT (Figure 1),10  incorporates the use of a clinical prediction rule to determine the pretest probability of disease and options for imaging (Table 3).19 The value of a laboratory test or imaging study in predicting the presence of PE depends on the likelihood of disease in each risk group.1921 The clinical prediction rule is most useful when a patient’s ventilation-perfusion scan is reported as showing intermediate or high probability.

Pulmonary Embolism

FIGURE 2.

Diagnosis of pulmonary embolism (PE). (CT = computed tomographic; VTE = venous thromboembolism)

Adapted with permission from Institute for Clinical Systems Improvement. Healthcare guidelines. Venous thromboembolism. Accessed online February 6, 2004, at: http://www.icsi.org/knowledge/detail.asp?catID=29&amp;itemID=202.

View Large

Pulmonary Embolism


FIGURE 2.

Diagnosis of pulmonary embolism (PE). (CT = computed tomographic; VTE = venous thromboembolism)

Adapted with permission from Institute for Clinical Systems Improvement. Healthcare guidelines. Venous thromboembolism. Accessed online February 6, 2004, at: http://www.icsi.org/knowledge/detail.asp?catID=29&amp;itemID=202.

Pulmonary Embolism


FIGURE 2.

Diagnosis of pulmonary embolism (PE). (CT = computed tomographic; VTE = venous thromboembolism)

Adapted with permission from Institute for Clinical Systems Improvement. Healthcare guidelines. Venous thromboembolism. Accessed online February 6, 2004, at: http://www.icsi.org/knowledge/detail.asp?catID=29&amp;itemID=202.

The presence of DVT can alter the probability of PE. This is especially useful when the helical CT scan is negative or the ventilation-perfusion scan is not diagnostic. The ICSI algorithm10 describes one rational approach to a complex and confusing area.

CLINICAL PREDICTION RULES

Wells clinical prediction rule for PE produces a point score based on clinical features and the likelihood of diagnoses other than PE.19 However, Wells rule has been criticized for the subjectivity of the judgment about other diagnoses, a problem that could affect the ability of physicians to apply the rule outside the research setting.

Other clinical prediction rules include the Geneva rule22 and the rule developed in the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISA-PED).23,24 However, the Geneva rule requires an arterial blood gas measurement and a chest radiograph, while the PISA-PED rule requires an ECG. One investigative team has developed rules for explicit use with d-dimer tests,25 and Wells rule has been simplified for use with d-dimer tests.19

No consensus has emerged on the best clinical prediction rule for PE or the criteria that should be used to judge the performance of the various rules. This article presents the original Wells clinical prediction rule19 to help guide physicians when d-dimer testing is not available. This prediction rule is one of the oldest and most frequently used decision rules. A low probability based on the combination of a prediction rule and a negative d-dimer test significantly reduces the probability of PE; however, the development of PE protocols awaits empiric validation.26

In the landmark PIOPED study,21 physicians were asked to use clinical judgment alone to categorize their clinical suspicion of PE as high, intermediate, or low. Despite the absence of standard or objective criteria, the PIOPED categorization has been validated, and even the most objective clinical prediction rules perform only marginally better than the physician’s subjective assessment.27 Therefore, subjective impression remains a good alternative to the use of a clinical prediction rule.

VENTILATION-PERFUSION SCANNING

For several decades, the ventilation-perfusion scan has been the first-line study in patients with suspected PE. Defects in radioactive tracer uptake from ventilated and perfused areas of the lungs are reported as normal, nearly normal, or indicating a low, intermediate, or high probability of embolus.

A high-probability ventilation-perfusion scan provides sufficient evidence for the initiation of treatment for PE. Likewise, a normal scan should be considered sufficient to exclude PE. Unfortunately, 50 to 70 percent of scans are indeterminate (low or intermediate probability). In the PIOPED study,21 40 percent of patients with confirmed PE had a high-probability ventilation-perfusion scan, 40 percent had an intermediate-probability scan, and 14 percent had a low-probability scan. Note that a low-probability scan does not rule out PE.21

TABLE 3

Wells Clinical Prediction Rule for PE

Clinical feature Points

Clinical symptoms of DVT

3

Other diagnosis less likely than PE

3

Heart rate greater than 100 beats per minute [corrected]

1.5

Immobilization or surgery within past 4 weeks

1.5

Previous DVT or PE

1.5

Hemoptysis

1

Malignancy

1

Total points:


PE = pulmonary embolism; DVT = deep venous thrombosis.

Risk score interpretation (probability of DVT): >6 points: high risk (78.4%); 2 to 6 points: moderate risk (27.8%); <2 points: low risk (3.4%)

Adapted with permission from 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 model utility with the SimpliREDd-dimer. Thromb Haemost 2000;83:418.

TABLE 3   Wells Clinical Prediction Rule for PE

View Table

TABLE 3

Wells Clinical Prediction Rule for PE

Clinical feature Points

Clinical symptoms of DVT

3

Other diagnosis less likely than PE

3

Heart rate greater than 100 beats per minute [corrected]

1.5

Immobilization or surgery within past 4 weeks

1.5

Previous DVT or PE

1.5

Hemoptysis

1

Malignancy

1

Total points:


PE = pulmonary embolism; DVT = deep venous thrombosis.

Risk score interpretation (probability of DVT): >6 points: high risk (78.4%); 2 to 6 points: moderate risk (27.8%); <2 points: low risk (3.4%)

Adapted with permission from 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 model utility with the SimpliREDd-dimer. Thromb Haemost 2000;83:418.

HELICAL COMPUTED TOMOGRAPHY

Studies indicate that helical CT scanning detects large PEs, with a sensitivity and specificity of nearly 90 percent for the identification of main and lobar emboli. However, this imaging modality generally is unable to detect smaller PEs.28

One potential advantage of helical CT scanning is its ability to identify an alternative diagnosis in about two thirds of cases in which PE is not present.29,30 A potential disadvantage is the identification of suspicious-appearing abnormalities that require further evaluation or even biopsy but actually are benign. Current use of helical CT scanning is determined by its availability. This imaging modality often is used to supplement other diagnostic tests (e.g., ventilation-perfusion scanning) when such tests are nondiagnostic.

At this time, helical CT scanning does not have sufficient resolution to justify its widespread adoption. Moreover, use of the imaging technique has not been unequivocally demonstrated to improve patient outcomes. As thin-collimation CT technology advances and resolution increases to the point that reliable evaluation of subsegmental vessels is possible, helical CT scanning may replace pulmonary angiography as the gold standard in the diagnosis of PE.

Strength of Recommendations

Key clinical recommendations Strength of recommendation References

A well-validated clinical prediction rule provides a reliable estimate of the pretest probability of DVT.

A

8,14

A well-validated clinical prediction rule provides a reliable estimate of the pretest probability of PE.

A

19,22,25,27

Compression ultrasonography should be the initial test in patients with acute symptomatic DVT.

A

10,17

A d-dimer assay can be used as a negative prediction tool to reduce the need for further studies rule out DVT.

B

17


DVT = deep venous thrombosis; PE = pulmonary embolism.

Strength of Recommendations

View Table

Strength of Recommendations

Key clinical recommendations Strength of recommendation References

A well-validated clinical prediction rule provides a reliable estimate of the pretest probability of DVT.

A

8,14

A well-validated clinical prediction rule provides a reliable estimate of the pretest probability of PE.

A

19,22,25,27

Compression ultrasonography should be the initial test in patients with acute symptomatic DVT.

A

10,17

A d-dimer assay can be used as a negative prediction tool to reduce the need for further studies rule out DVT.

B

17


DVT = deep venous thrombosis; PE = pulmonary embolism.

One analysis31 suggests that in patients with suspected PE, helical CT scanning is as cost-effective as ventilation-perfusion scanning and Duplex ultrasound examination of the lower extremity, but only when combined with D-dimer testing. Two recent multicenter trials32,33 suggest that helical CT scanning is safe to use for ruling out PE, at least in patients with a low or intermediate clinical probability of embolism. PIOPED II12 should yield important information about the diagnostic role of helical CT scanning.

d-DIMER TESTS

Use of the new generation of d-dimer tests in combination with the Wells clinical prediction rule is effective in ruling out PE in patients who present to the emergency department.34 A negative d-dimer test may rule out PE in patients with a low to moderate pretest probability of thrombus and a nondiagnostic ventilation-perfusion scan.35

As with DVT,8,1114 it is prudent for physicians to know the specific type of d-dimer test for PE that is offered at their institution and to understand the properties of that test.1921 However, in a general office population, where the pretest probability of PE is lower than it is in an emergency department, the usefulness of the clinical prediction rule in ruling out PE in the low-risk patients declines proportionately.

TABLE A

Risk-Stratified Performance of Tests in PE*

Pretest probability of PE by Wells’ clinical prediction rules19(%)
High risk: 78.4% (CI, 69.2% to 86%) Intermediate risk: 27.8% (CI, 23.4% to 32.2%) Low risk: 3.4% (CI, 2.2% to 5.0%)
Test Sensitivity (%) Specificity (%) PPV NPV PPV NPV PPV NPV

Helical computed tomography20

77

89

96

52

73

91

20

99

Magnetic resonance imaging20

77

87

96

51

70

91

17

99

Transthoracic echocardiography20

68

89

96

43

70

88

18

99

Transesophageal echocardiography20

70

81

93

43

59

88

12

99

d-dimer erythrocyte agglutination (SimpliRed)20

89

59

89

60

46

93

7

99

Ventilation-perfusion scanning21

98

10

80

58

30

93

3

99


PE = pulmonary embolism; CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value.

*—The Wells clinical prediction rule for PE (see print Table 3) is used to stratify patients according to risk status. Then PPV and NPV can be calculated using the pretest probability as the prevalence for the population sharing a given risk status. The pink areas represent a probability of PE of at least 90 percent based on a combination of the Wells clinical decision rule and the tests in the left-hand column. The blue areas represent the combination of patient risk and test that reduces the risk of PE to less than 5 percent.

Information from references 19 through 21.

TABLE A   Risk-Stratified Performance of Tests in PE*

View Table

TABLE A

Risk-Stratified Performance of Tests in PE*

Pretest probability of PE by Wells’ clinical prediction rules19(%)
High risk: 78.4% (CI, 69.2% to 86%) Intermediate risk: 27.8% (CI, 23.4% to 32.2%) Low risk: 3.4% (CI, 2.2% to 5.0%)
Test Sensitivity (%) Specificity (%) PPV NPV PPV NPV PPV NPV

Helical computed tomography20

77

89

96

52

73

91

20

99

Magnetic resonance imaging20

77

87

96

51

70

91

17

99

Transthoracic echocardiography20

68

89

96

43

70

88

18

99

Transesophageal echocardiography20

70

81

93

43

59

88

12

99

d-dimer erythrocyte agglutination (SimpliRed)20

89

59

89

60

46

93

7

99

Ventilation-perfusion scanning21

98

10

80

58

30

93

3

99


PE = pulmonary embolism; CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value.

*—The Wells clinical prediction rule for PE (see print Table 3) is used to stratify patients according to risk status. Then PPV and NPV can be calculated using the pretest probability as the prevalence for the population sharing a given risk status. The pink areas represent a probability of PE of at least 90 percent based on a combination of the Wells clinical decision rule and the tests in the left-hand column. The blue areas represent the combination of patient risk and test that reduces the risk of PE to less than 5 percent.

Information from references 19 through 21.

TABLE B

Risk-Stratified Performance of Tests in DVT*

Pretest probability of DVT by Wells’ clinical prediction rules8(%)
High risk: 75% (CI, 63% to 81%) Intermediate risk: 17% (CI, 12% to 23%) Low risk: 3% (CI, 1.7% to 5.9%)
Test Sensitivity (%) Specificity (%) PPV NPV PPV NPV PPV NPV

Impedence plethysmography11

77 to 98

83 to 97

93 to 99

55 to 94

48 to 87

95 to 100

12 to 50

99 to 100

Duplex ultrasonography11

88 to 97

80 to 96

93 to 99

69 to 91

47 to 83

97 to 99

12 to 42

99 to 100

Helical computed tomography12

71

93

97

52

68

94

24

99

Magnetic resonance imaging (for calf DVT)13

56 to 100

88 to 100

93

40

49

91

13

99

d-dimer testing14

89

77

39

89

14

99


DVT = deep venous thrombosis; CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value.

*—The Wells clinical prediction rule for DVT (see print Table 2) is used to stratify patients according to risk status. Then PPV and NPV can be calculated using the pretest probability as the prevalence for the population sharing a given risk status. The pink areas represent a probability of DVT of at least 90 percent based on a combination of the Wells clinical decision rule and the tests in the left-hand column. The blue areas represent the combination of patient risk and test that reduces the risk of DVT to well below 5 percent.

Information from references 8 and 11 through 14.

TABLE B   Risk-Stratified Performance of Tests in DVT*

View Table

TABLE B

Risk-Stratified Performance of Tests in DVT*

Pretest probability of DVT by Wells’ clinical prediction rules8(%)
High risk: 75% (CI, 63% to 81%) Intermediate risk: 17% (CI, 12% to 23%) Low risk: 3% (CI, 1.7% to 5.9%)
Test Sensitivity (%) Specificity (%) PPV NPV PPV NPV PPV NPV

Impedence plethysmography11

77 to 98

83 to 97

93 to 99

55 to 94

48 to 87

95 to 100

12 to 50

99 to 100

Duplex ultrasonography11

88 to 97

80 to 96

93 to 99

69 to 91

47 to 83

97 to 99

12 to 42

99 to 100

Helical computed tomography12

71

93

97

52

68

94

24

99

Magnetic resonance imaging (for calf DVT)13

56 to 100

88 to 100

93

40

49

91

13

99

d-dimer testing14

89

77

39

89

14

99


DVT = deep venous thrombosis; CI = confidence interval; PPV = positive predictive value; NPV = negative predictive value.

*—The Wells clinical prediction rule for DVT (see print Table 2) is used to stratify patients according to risk status. Then PPV and NPV can be calculated using the pretest probability as the prevalence for the population sharing a given risk status. The pink areas represent a probability of DVT of at least 90 percent based on a combination of the Wells clinical decision rule and the tests in the left-hand column. The blue areas represent the combination of patient risk and test that reduces the risk of DVT to well below 5 percent.

Information from references 8 and 11 through 14.

CHEST RADIOGRAPH AND ECG

In PIOPED,21 the ECGs were abnormal in 70 percent of patients with PE and no preexisting cardiovascular disease, but none of the electrocardiographic findings were specific or sensitive. In addition, only 12 percent of patients with PE had a normal chest radiograph. Again, the radiographic abnormalities (atelectasis, pulmonary parenchymal abnormality, pleural effusion, cardiomegaly) were neither specific nor sensitive for PE.

The Authors

DINO W. RAMZI, M.D., C.M., is assistant professor in the Department of Family and Preventive Medicine at Emory University School of Medicine, Atlanta. Dr. Ramzi graduated from McGill University, Montreal, Quebec, and completed graduate training in family medicine at Montreal General Hospital.

KENNETH V. LEEPER, M.D., is section chief of pulmonary and critical care at Crawford W. Long Memorial Hospital, Atlanta, medical director of the Clinical Studies Center at the Atlanta Veterans Affairs Medical Center, and associate professor in the Department of Internal Medicine at Emory University School of Medicine. He is one of the clinical investigators of the multicenter Prospective Investigation of Pulmonary Embolism Diagnosis II trial.

Address correspondence to Dino W. Ramzi, M.D., C.M., Department of Family and Preventive Medicine, Emory University School of Medicine, 4575 N. Shallowford Rd., Atlanta, GA 30338 (e-mail: dramzi@sph.emory.edu) Reprints are not available from the authors.

The authors indicate that they do not have any conflicts of interest. Sources of funding: none reported.

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2. Moser KM, LeMoine JR. Is embolic risk conditioned by location of deep venous thrombosis?. Ann Intern Med. 1981;94(4 pt 1):439–44.

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4. Ramzi DW, Leeper KV. DVT and pulmonary embolism: Part II. Treatment and prevention. Am Fam Physician. 2004;69:2841–8.

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Members of various medical faculties develop articles for “Practical Therapeutics.” This article is one in a series coordinated by the Department of Family and Preventive Medicine at Emory University School of Medicine, Atlanta. Guest editor of the series is Timothy Clenney, M.D.



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