Purpose The diagnosis of pulmonary embolism (PE) remains elusive due to the non-specific presentation of patients with the disease. The D-dimer blood test has been proven effective in ruling-out PE in patients stratified into a low-risk category, yet no study has confirmed its effectiveness in those with a moderate or high pre-test probability (PTP). This study attempts to determine the clinical outcomes of patients categorized as moderate to high risk for PE who had negative D-dimer test results (≤500 ng/mL.)
Methods A prospective study was performed based on the current University of Colorado Hospital protocol for patients suspected of PE between 1/24/03 and 8/4/04. Patients were enrolled when a D-dimer test was ordered for suspected PE and a research assistant was available. Two physicians (attending and senior resident) ranked PTP on a validated point scale and on their clinical gestalt. Subsequent tests were reviewed and ≥3-month follow-up was performed on all patients with moderate or high PTP and negative D-dimer results.
Results Among the 259 patients enrolled in the study between 1/24/03 and 8/4/04, 44 had a non-low PTP according to Wells assessment by the attending physician. Seventeen of these patients had radiological imaging studies during their visit (15 CTPE, 2 V/Q). All of these studies were negative for acute PE. Twenty-four patients (73%), out of a possible 33 for whom a 3-month window had elapsed, were available for follow-up. None of these patients were diagnosed with PE in the interim.
Conclusions The results suggest that a negative D-dimer result safely rules out acute PE in non-low PTP patients.