PE: A Clinical Challenge. Common: 250,000 cases/yearMimics many other illnessesPotentially fatal (15%)Treatment potentially dangerousNo single reliable diagnostic testUnder- and over-diagnosed. Diagnostic Testing. No single noninvasive test is sufficiently sensitive or specific to diagnose or exclude PE in all patientsNo single test can reliably rule out PEYep, that includes CT Angio (right?).