Pulmonary embolism diagnosis algorithm

Associate Editors-in-Chief: Ujjwal Rastogi, MBBS [mailto:urastogi@perfuse.org]

Overview
Signs and symptoms of pulmonary embolism are nonspecific; therefore, patients presenting with: —should undergo diagnostic tests until the diagnosis is confirmed or eliminated or an alternative diagnosis is made.
 * Unexplained dyspnea
 * Tachypnea
 * Chest pain
 * Risk factors for pulmonary embolism

CT equipped hospitals
In hospitals having experience in performing and interpreting CT Pulmonary angiography, following flowchart approach can be adopted.

CT Non-equipped hospitals
Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) Study proposed the following, for hospitals who do not have sufficient resources to perform or interpret CT Pulmonary angiography.

Wells criteria are used to assess the clinical probability of PE and its graded as Low, Intermediate or High. later a ventilation-perfusion scan (V/Q) is performed, and based on the result of the scan PE is diagnosed.

The following table summarizes the possible outcome of V/Q scan:

Low risk outpatient population
In populations with low PE prevalence, to avoid unnecessary and costly diagnostic interventions, the following factors were proposed, that formed the PE Rule-out Criteria(PERC):
 * Age less than 50 years
 * Heart rate less than 100 bpm
 * Oxyhemoglobin saturation ≥95 percent
 * No hemoptysis
 * No estrogen use
 * No prior DVT or PE
 * No unilateral leg swelling
 * No surgery or trauma requiring hospitalization within the past four weeks.

This approach was tested in a multicenter study involving 8138 outpatients with suspected PE. Another study stated that the PERC-approach has a high negative predictive value and sensitivity when combined with a low probability of PE using the Wells criteria, but a low positive predictive value and specificity. Therefore, it can be stated, when combined with a clinical assessment of low risk for PE, this approach can exclude PE without additional diagnostic testing. However, in clinical settings with a higher prevalence of PE (>20%), the PERC based approach has significantly poor predictive value.