Normal D-dimer levels in patients with pulmonary embolism

Area of Science:

• Medical Diagnostics
• Cardiovascular Medicine
• Radiology

Background:

• Pulmonary embolism (PE) diagnosis is difficult in acute care settings.
• Ventilation-perfusion (V/Q) scans can be inconclusive.
• Pulmonary angiograms (PAGs) are invasive and often unavailable.

Purpose of the Study:

• To evaluate the relationship between PE, V/Q scans, and latex agglutination (LA) D-dimer levels.
• To assess the diagnostic utility of LA D-dimer assays in suspected PE cases.
• To compare LA D-dimer results with pulmonary angiogram (PAG) findings.

Main Methods:

• Ninety-eight patients with suspected PE underwent V/Q scanning and PAG.
• Blood samples were collected for LA D-dimer assays during PAG.
• Medical records were reviewed for patient demographics and clinical data.

Main Results:

• Eight patients (27%) with positive PAG results had LA D-dimer levels below 250 ng/mL.
• In patients with low-probability V/Q scans, a positive D-dimer (>250 ng/mL) showed 71.4% sensitivity and 87.5% NPV.
• Mean D-dimer levels were significantly higher in patients with abnormal angiograms (750 ng/mL) vs. normal angiograms (250 ng/mL).

Conclusions:

• A normal LA D-dimer level alone does not exclude PE.
• Existing diagnostic algorithms using enzyme-linked immunosorbent assay (ELISA) D-dimer cannot be applied to LA assays.
• LA D-dimer results, with or without V/Q scans, should not be used to definitively rule out PE treatment.