The D-dimer test is a commonly used laboratory study that helps clinicians evaluate the presence of abnormal clot formation and breakdown within the body. It plays a key role in the assessment of suspected thromboembolic conditions such as pulmonary embolism and deep vein thrombosis.

Because these conditions can present with nonspecific symptoms, the D-dimer test serves as a valuable screening tool in clinical decision-making.

Understanding how it works, what it measures, and how to interpret the results is essential for respiratory therapists and other healthcare professionals involved in patient care.

What Is the D-Dimer Test?

The D-dimer test measures the presence of D-dimer, a protein fragment produced during the breakdown of cross-linked fibrin. Fibrin is a structural protein that forms the framework of a blood clot. When the body activates the coagulation cascade, fibrin strands are created to stabilize the clot. As part of the natural healing process, the fibrinolytic system later breaks down this clot, releasing D-dimer into the bloodstream.

Because D-dimer is only produced when a clot has formed and is being degraded, its presence serves as an indirect marker of recent or ongoing clotting activity. This makes the test particularly useful in identifying conditions where abnormal clot formation is suspected.

Physiology of D-Dimer Formation

To understand the significance of the D-dimer test, it is important to review the underlying physiology of coagulation and fibrinolysis.

Coagulation Cascade

The coagulation cascade is a complex series of enzymatic reactions that leads to the formation of a blood clot. It involves two primary pathways, the intrinsic and extrinsic pathways, which converge into a common pathway. The final step in this process is the conversion of fibrinogen, a soluble plasma protein, into fibrin by the action of thrombin.

Fibrin strands then cross-link to form a stable clot that helps stop bleeding. This process is essential for maintaining hemostasis and preventing excessive blood loss.

Fibrinolysis

Once the clot has served its purpose, the body initiates fibrinolysis to break it down. Plasmin, an enzyme derived from plasminogen, degrades fibrin into smaller fragments. One of these fragments is D-dimer, which is released into the circulation.

Because D-dimer is formed only from cross-linked fibrin, it is considered a specific marker of clot breakdown rather than simple fibrinogen degradation.

Clinical Indications for the D-Dimer Test

The D-dimer test is most commonly used in the evaluation of thromboembolic disorders. It is not intended to confirm a diagnosis but rather to help rule out certain conditions when used appropriately.

Pulmonary Embolism

Pulmonary embolism occurs when a blood clot, typically originating in the deep veins of the lower extremities, travels to the pulmonary arteries and obstructs blood flow. This can lead to impaired gas exchange, hypoxemia, and increased strain on the right side of the heart.

Patients with pulmonary embolism may present with symptoms such as shortness of breath, chest pain, tachycardia, and hypoxemia. However, these symptoms are not specific, making diagnosis challenging.

The D-dimer test is valuable in this context because:

• A normal result can help exclude pulmonary embolism in low-risk patients
• An elevated result suggests the need for further diagnostic imaging

Deep Vein Thrombosis

Deep vein thrombosis involves the formation of a clot in the deep veins, most commonly in the legs. Symptoms may include swelling, pain, redness, and warmth in the affected limb.

As with pulmonary embolism, the D-dimer test is used as a screening tool:

• A negative result can help rule out DVT in patients with low clinical probability
• A positive result requires confirmation with imaging, such as ultrasound

Role as a Screening Tool

One of the most important characteristics of the D-dimer test is its high sensitivity. This means that it is very effective at detecting the presence of clot formation and breakdown when it is occurring.

High Sensitivity

In patients with conditions such as pulmonary embolism or deep vein thrombosis, D-dimer levels are typically elevated. Because of this, a normal D-dimer level makes these conditions unlikely.

This property gives the test a high negative predictive value, especially in patients with low pretest probability.

Low Specificity

Despite its high sensitivity, the D-dimer test has low specificity. Elevated levels are not unique to thromboembolic disease and can occur in many other conditions.

Examples include:

• Infection
• Inflammation
• Recent surgery
• Trauma
• Pregnancy
• Liver disease
• Malignancy
• Advanced age

Note: Because of this, a positive D-dimer result does not confirm the presence of a clot. Instead, it indicates that further evaluation is needed.

Pretest Probability and Clinical Decision-Making

The D-dimer test should never be used in isolation. Its interpretation depends heavily on the clinical context and the patient’s pretest probability of disease.

Assessing Pretest Probability

Before ordering a D-dimer test, clinicians typically assess the likelihood of pulmonary embolism or deep vein thrombosis using clinical judgment or scoring systems.

Factors that may increase suspicion include:

• Recent immobilization
• Surgery
• History of thromboembolism
• Cancer
• Signs of DVT
• Unexplained hypoxemia

Low Pretest Probability

In patients with low clinical suspicion:

• A negative D-dimer effectively rules out thromboembolic disease
• No further testing is usually required

Note: This approach helps avoid unnecessary imaging and reduces patient exposure to radiation and contrast agents.

Moderate to High Pretest Probability

In patients with moderate or high suspicion:

• Imaging studies are required regardless of the D-dimer result
• A negative D-dimer may not be sufficient to exclude disease

Note: This highlights the importance of integrating laboratory data with clinical assessment.

Diagnostic Follow-Up Testing

When a D-dimer test is elevated, additional diagnostic studies are necessary to confirm or exclude thromboembolic disease.

CT Pulmonary Angiography

CT pulmonary angiography is the preferred imaging study for diagnosing pulmonary embolism. It provides detailed visualization of the pulmonary arteries and can identify the presence of clots.

Ventilation-Perfusion Scan

A ventilation-perfusion scan evaluates the distribution of air and blood flow in the lungs. It is often used when CT angiography is contraindicated, such as in patients with renal impairment or contrast allergy.

Venous Ultrasound

For suspected deep vein thrombosis, venous ultrasound is the primary imaging modality. It allows visualization of blood flow and detection of clots in the veins.

Reference Values and Laboratory Variability

D-dimer levels are reported in different units depending on the assay used by the laboratory. Common reference ranges include:

• Less than 240 ng/mL
• Less than 400 ng/mL

These variations reflect differences in testing methods and sensitivity. Clinicians must interpret results based on the specific reference range provided by the laboratory.

Some institutions also use age-adjusted D-dimer thresholds, particularly in older adults, to improve specificity and reduce false-positive results.

Limitations of the D-Dimer Test

While the D-dimer test is a valuable tool, it has several important limitations that must be considered.

False Positives

Many conditions can elevate D-dimer levels, leading to false-positive results. This can result in unnecessary imaging and increased healthcare costs.

Reduced Utility in Hospitalized Patients

In hospitalized or critically ill patients, D-dimer levels are often elevated due to underlying illness, inflammation, or recent procedures. In these cases, the test becomes less useful for ruling out thromboembolic disease.

Lack of Specificity for Clot Location

The D-dimer test does not provide information about the location or size of a clot. It simply indicates that clot formation and breakdown have occurred.

Limited Role in Monitoring

D-dimer is not typically used to monitor treatment response or disease progression. Its primary role is in initial screening and evaluation.

D-Dimer in Other Clinical Conditions

Although most commonly associated with pulmonary embolism and deep vein thrombosis, the D-dimer test can also be elevated in other conditions involving abnormal coagulation.

Disseminated Intravascular Coagulation

Disseminated intravascular coagulation is a serious condition characterized by widespread activation of the coagulation cascade. This leads to the formation of multiple small clots throughout the body, followed by increased fibrinolysis.

Note: D-dimer levels are often markedly elevated in this condition, reflecting extensive clot breakdown.

Infection and Inflammation

Systemic infections and inflammatory conditions can activate the coagulation system, leading to increased D-dimer levels. This is commonly seen in severe illnesses and critical care settings.

Relevance to Respiratory Care

For respiratory therapists, the D-dimer test is particularly important because pulmonary embolism directly affects the cardiopulmonary system.

A pulmonary embolism can lead to:

• Ventilation-perfusion mismatch
• Increased dead space ventilation
• Hypoxemia
• Right ventricular strain

Recognizing the role of D-dimer in the diagnostic process helps respiratory therapists contribute to early identification and management of these conditions.

In clinical practice, therapists may:

• Review laboratory results
• Identify abnormal D-dimer levels
• Communicate findings to the healthcare team
• Support further diagnostic evaluation

Integration into Patient Assessment

The use of the D-dimer test reflects a broader principle in patient care. No single test should be used in isolation. Instead, clinicians must integrate multiple sources of information, including:

• Patient history
• Physical examination findings
• Laboratory results
• Imaging studies

Note: By combining these elements, healthcare providers can make more accurate and informed decisions.

Advanced Interpretation and Clinical Nuances

Age-Adjusted D-Dimer

One important refinement in the use of the D-dimer test is the concept of age-adjusted thresholds. As patients age, baseline D-dimer levels tend to increase even in the absence of thromboembolic disease. This reduces the specificity of the test and leads to a higher rate of false-positive results in older adults.

To address this, many institutions use an age-adjusted cutoff for patients over 50 years old. A commonly used formula is:

• Age × 10 ng/mL (for assays reported in fibrinogen equivalent units)

For example, a 70-year-old patient would have an adjusted cutoff of 700 ng/mL rather than the standard 500 ng/mL threshold. This approach improves specificity while maintaining sensitivity, reducing unnecessary imaging without increasing the risk of missed diagnoses.

Units and Assay Types

D-dimer results can be reported in different units depending on the assay used. The two most common are:

• D-dimer units (DDU)
• Fibrinogen equivalent units (FEU)

FEU values are approximately twice those of DDU for the same sample. For example:

• 500 ng/mL FEU ≈ 250 ng/mL DDU

Note: Understanding the reporting system used by a specific laboratory is essential for accurate interpretation. Misinterpretation of units can lead to incorrect clinical decisions.

Causes of Elevated D-Dimer

Because D-dimer reflects fibrin breakdown, any condition that activates the coagulation and fibrinolytic systems can lead to elevated levels. This is the primary reason for its low specificity.

Common causes include:

• Acute infection and sepsis
• Inflammatory disorders
• Recent surgery or trauma
• Pregnancy and the postpartum period
• Malignancy
• Liver disease
• Advanced age
• Hospitalization and critical illness

Note: In these settings, an elevated D-dimer should be interpreted with caution, as it may not indicate thromboembolic disease.

False-Negative Results

Although the D-dimer test is highly sensitive, false-negative results can occur in certain situations.

These include:

• Very early testing before significant clot breakdown has occurred
• Small or isolated clots
• Chronic thromboembolic disease
• Use of anticoagulant therapy prior to testing

Note: Because of this, a negative D-dimer should not override strong clinical suspicion in moderate or high-risk patients.

D-Dimer vs. Other Diagnostic Markers

Distinction from Cardiac Biomarkers

In clinical practice, it is important to differentiate between pulmonary embolism and myocardial infarction, as both conditions can present with chest pain and shortness of breath.

D-dimer is associated with thromboembolic disease, whereas myocardial infarction is diagnosed using cardiac biomarkers such as:

• Troponin I
• Creatine kinase-MB

Note: These markers reflect myocardial injury rather than clot breakdown. Using the correct test for the suspected condition is essential for accurate diagnosis.

Comparison with Other Coagulation Tests

D-dimer is one component of a broader set of coagulation studies. Other tests include:

• Prothrombin time (PT)
• Activated partial thromboplastin time (aPTT)
• Platelet count

Note: While these tests evaluate different aspects of the coagulation system, D-dimer specifically reflects fibrin degradation and is most useful for detecting active clot turnover.

Role in Clinical Scenarios and Exam Preparation

For respiratory therapy students and clinicians preparing for the board examination, the D-dimer test is a high-yield topic.

Information Gathering

In exam scenarios, selecting the D-dimer test when pulmonary embolism is suspected is considered an appropriate step in information gathering. It demonstrates an understanding of which diagnostic tools are relevant for specific conditions.

Decision Making

After reviewing results, the clinician must determine the next step:

• A normal D-dimer in a low-risk patient supports ruling out pulmonary embolism
• An elevated D-dimer requires further diagnostic imaging

Note: Choosing the correct next step is critical for scoring well in clinical simulation examinations.

D-Dimer and Pulmonary Embolism Pathophysiology

Pulmonary embolism has a direct impact on respiratory function, making it highly relevant in respiratory care.

Ventilation-Perfusion Mismatch

When a clot obstructs a pulmonary artery, blood flow to that region of the lung is reduced or absent. Ventilation may remain normal, leading to a mismatch between ventilation and perfusion.

This results in:

• Increased dead space ventilation
• Reduced oxygen uptake

Hypoxemia

The mismatch between ventilation and perfusion contributes to decreased arterial oxygen levels. Patients may present with hypoxemia that is not fully corrected by supplemental oxygen.

Cardiovascular Effects

Large or multiple emboli can increase pulmonary vascular resistance, leading to:

• Right ventricular strain
• Decreased cardiac output
• Potential hemodynamic instability

Note: The presence of elevated D-dimer in this context supports the suspicion of pulmonary embolism and guides further evaluation.

Clinical Workflow for Suspected Pulmonary Embolism

The D-dimer test is best understood within a structured clinical workflow.

Step 1: Assess Symptoms

Patients may present with:

• Sudden onset dyspnea
• Chest pain
• Tachycardia
• Hypoxemia

Step 2: Determine Risk Level

Clinical assessment is used to estimate the likelihood of pulmonary embolism.

Step 3: Order D-Dimer

If the patient is low risk:

• A D-dimer test is appropriate

Step 4: Interpret Results

• Negative result: pulmonary embolism is unlikely
• Positive result: further testing is required

Step 5: Perform Imaging

Confirmatory testing may include:

• CT pulmonary angiography
• Ventilation-perfusion scan

Note: This stepwise approach ensures efficient and accurate diagnosis while minimizing unnecessary procedures.

Special Populations

Pregnancy

D-dimer levels are naturally elevated during pregnancy due to increased coagulation activity. This limits the usefulness of the test in pregnant patients and often necessitates direct imaging when pulmonary embolism is suspected.

Elderly Patients

As previously discussed, D-dimer levels increase with age. Age-adjusted thresholds can improve diagnostic accuracy in this population.

Critically Ill Patients

In critically ill patients, D-dimer levels are frequently elevated due to systemic inflammation and other factors. This reduces its utility as a rule-out test in intensive care settings.

Cost-Effectiveness and Patient Safety

One of the primary advantages of the D-dimer test is its role in reducing unnecessary imaging.

Avoiding Unnecessary CT Scans

CT pulmonary angiography exposes patients to:

• Ionizing radiation
• Intravenous contrast agents

Note: By using D-dimer appropriately in low-risk patients, clinicians can avoid these risks when the test result is negative.

Reducing Healthcare Costs

Limiting unnecessary imaging also reduces healthcare costs and resource utilization. This aligns with the broader goal of providing efficient and evidence-based care.

Common Pitfalls in Interpretation

Despite its usefulness, the D-dimer test is often misinterpreted.

• Overreliance on Positive Results: A common mistake is assuming that an elevated D-dimer confirms pulmonary embolism. In reality, it only indicates the need for further testing.
• Ignoring Clinical Context: Interpreting D-dimer results without considering the patient’s clinical presentation can lead to incorrect conclusions.
• Inappropriate Use in High-Risk Patients: Ordering a D-dimer test in patients with high pretest probability may delay definitive imaging and appropriate treatment.

Key Takeaways for Clinical Practice

• D-dimer is a marker of fibrin degradation
• It is highly sensitive but not specific
• A normal result helps rule out thromboembolic disease in low-risk patients
• An elevated result requires further diagnostic evaluation
• It must always be interpreted in clinical context

D-Dimer Test Practice Questions

1. What does the D-dimer test measure?
D-dimer measures fibrin degradation products formed after clot breakdown.

2. What is the primary clinical use of the D-dimer test?
It is used as a screening tool to help rule out thromboembolic disease.

3. Which two conditions are most commonly evaluated using D-dimer?
Pulmonary embolism (PE) and deep vein thrombosis (DVT).

4. Why is D-dimer considered highly sensitive?
Because it is almost always elevated when clot formation and breakdown are present.

5. What does a normal D-dimer level suggest in a low-risk patient?
It helps rule out thromboembolic disease.

6. Why is D-dimer considered nonspecific?
Because it can be elevated in many conditions unrelated to thrombosis.

7. Name one non-thrombotic condition that can elevate D-dimer.
Infection

8. What protein is broken down to produce D-dimer?
Cross-linked fibrin

9. Which system is responsible for breaking down clots and producing D-dimer?
The fibrinolytic system.

10. What enzyme plays a key role in fibrin breakdown?
Plasmin

11. Does an elevated D-dimer confirm pulmonary embolism?
No, it only suggests the need for further testing.

12. What type of test is D-dimer considered in clinical practice?
A screening and rule-out test.

13. What imaging study is commonly used after a positive D-dimer for PE?
CT pulmonary angiography

14. What imaging test is used to confirm suspected DVT?
Venous ultrasound

15. What is the main limitation of the D-dimer test?
Low specificity

16. Why should D-dimer not be used alone in diagnosis?
Because it must be interpreted in clinical context.

17. What is pretest probability?
An estimate of the likelihood that a patient has a specific condition.

18. In which patients is D-dimer most useful?
Patients with low pretest probability of thromboembolism.

19. What happens if D-dimer is elevated in a low-risk patient?
Further diagnostic imaging is required.

20. Why is D-dimer less useful in hospitalized patients?
Because many factors can cause false-positive elevations.

21. What does fibrin formation indicate?
Activation of the coagulation cascade.

22. What does fibrin degradation indicate?
Clot breakdown

23. Can D-dimer indicate the size of a clot?
No, it does not correlate with clot size.

24. What condition involves widespread clotting and elevated D-dimer?
Disseminated intravascular coagulation (DIC).

25. What is one symptom common to both PE and MI?
Chest pain

26. What is the main purpose of using D-dimer in suspected PE cases?
To help rule out pulmonary embolism in low-risk patients.

27. What type of protein fragment is D-dimer classified as?
A fibrin degradation product.

28. What process converts fibrinogen into fibrin?
The coagulation cascade.

29. Which factor stabilizes a blood clot to allow D-dimer formation later?
Cross-linking of fibrin strands.

30. What is the role of thrombin in clot formation?
It converts fibrinogen into fibrin.

31. Why is D-dimer not useful for confirming myocardial infarction?
Because it reflects clot breakdown, not cardiac muscle injury.

32. Which lab markers are used instead for diagnosing myocardial infarction?
Troponin I and CK-MB.

33. What type of value does D-dimer have when negative?
High negative predictive value.

34. What is the significance of a positive D-dimer in clinical practice?
It indicates the need for further diagnostic evaluation.

35. What is one risk of unnecessary CT pulmonary angiography?
Exposure to ionizing radiation.

36. What is another risk of CT pulmonary angiography?
Exposure to intravenous contrast agents.

37. Why is minimizing unnecessary imaging important?
To reduce patient risk and healthcare costs.

38. What clinical setting makes D-dimer interpretation more difficult?
Critical care or hospitalized settings.

39. What underlying condition can cause elevated D-dimer in ICU patients?
Systemic inflammation

40. What does an elevated D-dimer indicate about fibrin activity?
Increased fibrin formation and breakdown.

41. Can chronic clots always produce elevated D-dimer levels?
No, they may not always result in high levels.

42. What happens to pulmonary blood flow during a pulmonary embolism?
It becomes obstructed.

43. What type of mismatch occurs in PE affecting gas exchange?
Ventilation-perfusion mismatch

44. What effect does PE have on dead space ventilation?
It increases dead space ventilation.

45. What is a common oxygenation issue seen in PE?
Hypoxemia

46. What cardiac complication can result from a large PE?
Right ventricular strain

47. Why is early identification of PE important?
To prevent serious complications and improve outcomes.

48. What step should be taken after identifying an abnormal D-dimer?
Recommend or perform imaging studies.

49. What does clinical judgment determine before ordering D-dimer?
Pretest probability of disease.

50. What is one example of a risk factor for thromboembolism?
Recent surgery

51. What does a D-dimer test indirectly reflect about the body?
Recent or ongoing activation of the coagulation and fibrinolytic systems.

52. Why is D-dimer not elevated in myocardial infarction alone?
Because MI involves tissue damage rather than systemic clot breakdown.

53. What is the origin of most pulmonary emboli?
Deep veins of the lower extremities.

54. What is the role of plasminogen in fibrinolysis?
It is converted into plasmin to break down fibrin.

55. What type of patients benefit most from a D-dimer test?
Ambulatory or emergency department patients with low clinical suspicion.

56. What does a low D-dimer level indicate about fibrin turnover?
Minimal or no recent clot formation and breakdown.

57. What clinical scenario reduces the reliability of D-dimer results?
Recent trauma or surgery.

58. What happens to D-dimer levels during pregnancy?
They increase due to enhanced coagulation activity.

59. What is one consequence of low specificity in D-dimer testing?
Higher rates of false-positive results.

60. What does D-dimer help clinicians decide in patient management?
Whether further diagnostic testing is necessary.

61. What is the relationship between D-dimer and fibrinogen?
D-dimer is produced after fibrinogen is converted to fibrin and then degraded.

62. Why is D-dimer not useful for determining clot location?
Because it only indicates clot presence, not where it is.

63. What clinical sign might increase suspicion for DVT?
Unilateral leg swelling.

64. What is one advantage of using D-dimer in evaluation?
It is a noninvasive blood test.

65. What does a high D-dimer suggest in terms of clot activity?
Active clot formation and breakdown.

66. What is the effect of liver disease on D-dimer levels?
It can cause elevated levels due to impaired metabolism.

67. What does the presence of D-dimer confirm about fibrin?
That it has been cross-linked and degraded.

68. What is one key limitation when using D-dimer in elderly patients?
Baseline levels are often elevated.

69. What role does D-dimer play in differential diagnosis?
It helps distinguish thromboembolic conditions from other causes.

70. What is a common presenting symptom of pulmonary embolism?
Shortness of breath

71. Why might D-dimer be elevated in cancer patients?
Due to increased coagulation activity.

72. What is one reason clinicians avoid overusing D-dimer testing?
It may lead to unnecessary follow-up procedures.

73. What does a normal D-dimer indicate about clot presence?
It makes significant thromboembolism unlikely in low-risk patients.

74. What is one physiological process that must occur before D-dimer is formed?
Cross-linking of fibrin.

75. Why is understanding D-dimer important for respiratory therapists?
It helps guide evaluation of suspected pulmonary embolism.

76. What stage of hemostasis must occur before D-dimer can be detected?
Formation and stabilization of a fibrin clot.

77. What does the presence of D-dimer indicate about fibrinolysis?
That fibrinolysis is actively breaking down a clot.

78. Why is D-dimer useful in emergency department settings?
It helps rapidly rule out PE in low-risk patients.

79. What type of clinical tool is often used before ordering D-dimer?
A clinical prediction rule or scoring system.

80. What is one consequence of elevated D-dimer in non-thrombotic conditions?
It can lead to unnecessary imaging studies.

81. What is the relationship between D-dimer and thrombus age?
Levels may be lower in older or chronic clots.

82. Why might early testing yield a normal D-dimer in PE?
Insufficient time has passed for fibrin breakdown.

83. What type of clot produces D-dimer when degraded?
A cross-linked fibrin clot.

84. What is one limitation of D-dimer in diagnosing isolated distal DVT?
It may not be significantly elevated.

85. What role does D-dimer play in clinical exclusion strategies?
It helps safely exclude thromboembolism in low-risk patients.

86. What is one factor that increases baseline D-dimer levels with age?
Age-related changes in coagulation activity.

87. What does an elevated D-dimer suggest about coagulation activity?
Increased activation of the clotting system.

88. What is one advantage of using D-dimer before imaging?
It can reduce unnecessary radiation exposure.

89. What type of patients may require imaging regardless of D-dimer results?
Patients with high clinical suspicion of PE.

90. What is one symptom that may prompt D-dimer testing?
Unexplained hypoxemia

91. What is one reason D-dimer is not used as a standalone diagnostic test?
It lacks specificity for thromboembolic disease.

92. What does D-dimer reflect in terms of fibrin structure?
Breakdown of cross-linked fibrin.

93. What is one reason D-dimer may be elevated after surgery?
Tissue injury activates the coagulation cascade.

94. What type of ventilation issue occurs in PE?
Increased physiologic dead space.

95. What is one benefit of a negative D-dimer in low-risk patients?
Avoidance of further invasive or costly tests.

96. What is the clinical significance of persistent D-dimer elevation?
Ongoing coagulation and fibrinolysis activity.

97. What is one reason D-dimer levels rise in systemic illness?
Inflammatory activation of clotting pathways.

98. What is one diagnostic step after a positive D-dimer for suspected DVT?
Perform a venous ultrasound.

99. What does D-dimer testing help reduce in healthcare systems?
Unnecessary imaging and associated costs.

100. What is the overall role of D-dimer in patient care?
To aid in ruling out thromboembolic disease when used appropriately.

Final Thoughts

The D-dimer test is an important component of the diagnostic process for thromboembolic disease, particularly pulmonary embolism and deep vein thrombosis. Its strength lies in its ability to help rule out these conditions when used in the appropriate clinical setting.

However, its limitations require careful interpretation and integration with patient assessment and imaging studies.

For respiratory therapists and healthcare professionals, understanding when and how to use the D-dimer test supports accurate diagnosis, improves patient safety, and enhances overall clinical decision-making in both practice and exam scenarios.