The present invention comprises a method for identifying the presence or absence of a pulmonary embolism using a combination of tests and brightline thresholds. The first test is a blood based test measuring D-Dimer concentration and the second test is a respiratory analysis that determines a carboximetry ratio. If the measured D-Dimer value is at or above a threshold indicative of concern and the carboximetry value is equal to or less than a carboximetry ratio threshold, pulmonary embolism is present. If the measured D-Dimer value is at or above a threshold indicative of concern and the respiratory analysis yields a carboximetry ratio greater than the carboximetry ratio threshold, test results are inconclusive and additional testing is required to determine whether a pulmonary embolism is present.
