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.