From the Guidelines
A D-dimer test in patients with pneumonia (PNA) and chronic obstructive pulmonary disease (COPD) has limited diagnostic value due to frequent false positives, and its primary value lies in its negative predictive value to rule out pulmonary embolism (PE) when the result is below the age-adjusted cutoff. D-dimer levels often become elevated in these conditions due to the inflammatory processes involved, even without thromboembolism. In patients with PNA and COPD who present with symptoms suggesting possible PE, a normal D-dimer can help rule out PE, but an elevated result cannot confirm it. The test's specificity decreases further during acute COPD exacerbations or severe pneumonia.
When evaluating these patients for possible thromboembolism, clinicians should consider using age-adjusted D-dimer cutoffs (age × 10 ng/mL for patients over 50) as recommended by the American College of Physicians 1. This approach is supported by best practice advice that suggests using validated clinical prediction rules to estimate pretest probability and obtaining a high-sensitivity d-dimer measurement as the initial diagnostic test in patients with intermediate pretest probability of PE or in patients with low pretest probability of PE who do not meet all Pulmonary Embolism Rule-Out Criteria.
Key points to consider include:
- Using age-adjusted d-dimer thresholds to determine the need for imaging studies 1
- Not obtaining any imaging studies in patients with a d-dimer level below the age-adjusted cutoff 1
- Obtaining imaging with CT pulmonary angiography (CTPA) in patients with high pretest probability of PE, reserving ventilation–perfusion scans for patients with contraindications to CTPA or when CTPA is not available 1
- The importance of clinical probability scores like the Wells score in evaluating patients for possible thromboembolism 1
By following these guidelines and considering the limitations and appropriate use of D-dimer testing in patients with PNA and COPD, clinicians can improve the diagnostic accuracy for PE and reduce unnecessary imaging studies, thereby optimizing patient outcomes in terms of morbidity, mortality, and quality of life.
From the Research
D-dimer and Pulmonary Embolism (PE) Diagnosis
- The D-dimer test has limited diagnostic value for PE in patients with chronic obstructive pulmonary disease (COPD) exacerbation, as it can be elevated in COPD patients without PE 2, 3.
- A study found that the combination of D-dimer level and Wells score had an acceptable diagnostic value for PE diagnosis in COPD patients, with a sensitivity of 47.37% and specificity of 88.17% 2.
- Another study suggested that the cut-off value for D-dimer in diagnosing PE in COPD patients should be reevaluated, as the current cut-off value may lead to false positives 3.
D-dimer and Pneumonia (PNA)
- D-dimer levels can be elevated in patients with community-acquired pneumonia, making it difficult to differentiate between pneumonia and PE using D-dimer alone 4.
- A study found that D-dimer levels were higher in patients with pneumonia than in healthy controls, but lower than in patients with high-probability PE 4.
D-dimer as a Prognostic Biomarker
- Elevated D-dimer levels have been associated with increased mortality in patients with acute exacerbation of COPD (AECOPD) 5.
- A study found that D-dimer levels >1.52 mg/L predicted in-hospital mortality with a sensitivity of 100% and specificity of 63.6% in AECOPD patients 5.
- D-dimer has been suggested as a reliable prognostic marker for both short-term and long-term survival in patients with AECOPD 5.
Thrombocytopenia and Outcomes in PNA, COPD, and Asthma
- Thrombocytopenia has been associated with increased in-hospital mortality, prolonged length of stay, higher resource utilization, and increased intubation rates in patients with PNA, COPD, and asthma 6.
- Patients with asthma and thrombocytopenia had a significantly increased in-hospital mortality rate compared to those without thrombocytopenia 6.