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Principal Investigator:  Sarah E. Fowler, Ph.D.

The Prospective Investigation of Pulmonary Embolism Diagnosis III (PIOPED III) will estimate the diagnostic accuracy of gadolinium-enhanced magnetic resonance angiography of the pulmonary arteries (Gd-MRA) and Gd-MRA combined with gadolinium-enhanced magnetic resonance venography (MRV) for the diagnosis of acute pulmonary embolism (PE). Diagnostic accuracy will be expressed as the sensitivity, specificity, likelihood ratio for a positive test and likelihood ratio for a negative test. The reference test consists of the most definitive from among combinations of tests comprising standard of care for diagnosing PE: spiral CT/CTV angiogram/venogram, ventilation/perfusion lung scan, pulmonary angiogram, and compression US, d-Dimer, and standardized clinical assessment.

The study will enroll 1256 patients to determine the extent to which Gd-MRA or Gd-MRA/MRV can serve as a diagnostic test in patients with clinically suspected PE, and thereby eliminate the need for iodinated contrast material or ionizing radiation in patients who have a relative contraindication to one of them. This is important because 24% of patients with suspected acute PE have a relative contraindication to diagnostic procedures that involve ionizing radiation or iodinated contrast material.

Possible results of PIOPED III are that Gd-MRA or the combination Gd-MRA/MRV, can be used as: 1) a definitive diagnostic test in patients with suspected acute PE; 2) a definitive test to diagnose (but not exclude) PE; 3) a test to exclude (but not diagnose) PE; and 4) a definitive diagnostic test to diagnose PE in central pulmonary arteries, requiring additional tests to exclude PE in segmental or subsegmental arteries.

The Biostatistics Center serves as the Data Coordinating Center (DCC) for the study. In addition to data collection, data management, and statistical analysis, the DCC coordinates distribution of scan images to readers throughout the clinical centers for final interpretation.

The study is funded by the NIH/NHLBI through the cooperative agreement mechanism. (5U01-HL077155-01A1, 2005-2009).)