Context: Pulmonary embolism (PE) is a potentially fatal and frequent complication of deep venous thrombosis, and the most reliable techniques for the diagnosis of PE are not universally available and have other limitations.
Objective: To determine the efficacy of 4 different fibrinolysis system parameters, namely, tissue plasminogen activator (tPA), tissue plasminogen activator inhibitor type 1 (PAI-1), plasmin-antiplasmin complexes (PAP), and D-dimer, in the diagnosis of acute PE.
Setting: A 350-bed university hospital serving an area with 280,000 inhabitants.
Patients: Sixty-six consecutive outpatients with clinically suspected PE. The diagnosis of PE was based on ventilation-perfusion (V/Q) lung scan in combination with clinical assessment, lower limb study, and (when required) pulmonary angiography.
Main outcome measures: At the moment of clinical suspicion, a sample of venous blood was obtained to measure levels of tPA, PAI-1, PAP, and D-dimer using an enzyme-linked immunosorbent assay method.
Results: Twenty-seven patients (41%) were classified as PE positive (high clinical probability and V/Q lung scan [n = 12], nondiagnostic V/Q lung scan and high clinical probability [n = 1], inconclusive V/Q lung scan and positive lower limb examination for deep venous thrombosis [n = 11], and positive pulmonary angiography [n = 3]), and 39 patients (59%) were classified PE negative. The sensitivity/negative predictive value for tPA, using a cutoff of 8.5 ng/mL, and PAI-1, using a cutoff of 15 ng/mL, were 100%/100% and 100%/100%, respectively. A tPA level lower than 8.5 ng/mL occurred in 13 (19.7%; all PE negative) of 66 patients with suspected PE, and PAI-1 levels were lower than 15 ng/mL in 9 (13.6%; all PE negative) of 66 patients with suspected PE. The D-dimer, using a cutoff of 500 ng/mL, showed a sensitivity and negative predictive value of 92.6% and 87.5%, respectively.
Conclusions: Our data indicate that tPA and PAI-1 levels are potentially useful in ruling out PE, although tPA seems to be the better parameter. The sensitivity levels and negative predictive values for the rapid enzyme-linked immunosorbent assay for D-dimer used in this investigation were low compared with previous studies using the same test.