Can the tandem measurement of age adjusted D-dimer and tissue plasminagen activator improve the clinical utility of a conventional D-dimer in the pulmonary embolism diagnosis?

BACKGROUND: The aim of this study was to evaluate if a sequential measurement of age adjust D-dimer (ADD) and tissue plasminogen activator (tPA) could increase the clinical utility in patients with suspected pulmonary embolism (PE) compared to a conventional D-dimer. METHODS: We measured a conventional D-dimer (CDD), an ADD alone and a sequential combination ADD and tPA (ADD/tPA combination) in a prospective sample of 127 outpatients with PE suspected. Diagnosis of PE was based on a strict protocol. Plasma sample to measure levels of tPA and D-dimer was obtained at enrollment, and CDD, ADD and tPA were assessed at the end of study. For CDD the cut-off value was 500 ng/mL and for ADD the cut-off value was defined as (patient's age x10) ng/mL in patients aged >50. We compared the sensitivity, specificity and clinical utility obtained for CDD, ADD alone, and ADD/tPA combination. RESULTS: PE was confirmed in 41 patients (32%). The sensitivity, specificity and clinical utility for CDD were 95%, 36% and 28%, respectively. The ADD/tPA combination and ADD alone demonstrated an increased in specificity of +29% and +12% respectively, and increased in clinical utility of +20% and +8%, respectively, compared to CDD, and this was obtained without loss of sensitivity. CONCLUSION: The ADD/tPA combination substantially increased the clinical utility in the PE diagnosis compared with conventional D-dimer, without reducing the security. The ADD/tPA combination could decrease the need for pulmonary vascular imaging for the PE diagnosis in nearly the half. These promising results should be validated prospectively.