RESUMEN
CONTEXT: A previous study suggested that the combination of a normal D-dimer assay and normal alveolar dead-space fraction is a highly sensitive screening test for pulmonary embolism (PE). OBJECTIVE: To determine if the combination of a normal alveolar dead-space fraction (volume of alveolar dead space/tidal volume =20%) and a normal whole-blood agglutination D-dimer assay can exclude PE in emergency department (ED) patients. DESIGN: Prospective, noninterventional study conducted in 1998-1999. Study data were obtained prior to standard testing for PE, consisting of radionuclide lung scanning or contrast-enhanced computed tomography and 6-month follow-up plus selective use of venous ultrasonography and pulmonary angiography. Imaging studies were interpreted by blinded observers. SETTING: Six urban teaching hospitals in the United States. PATIENTS: A total of 380 hemodynamically stable ED patients aged 18 years or older with suspected acute PE. MAIN OUTCOME MEASURES: Sensitivity and specificity for PE with a positive test defined as having either alveolar dead-space fraction or D-dimer assay results abnormal. Alveolar dead-space fraction was determined by subtracting airway dead space from physiological dead space (determined using the modified Bohr equation) and D-dimer assay, assayed at bedside using 20 microL of arterial blood. RESULTS: Pulmonary embolism was diagnosed in 64 patients (16.8%), of those 20 had an abnormal D-dimer assay result, 3 had an abnormal alveolar dead-space fraction, 40 had abnormal results in both, and 1 had normal results for both tests. The sensitivity for diagnosis of PE was 98.4% (95% confidence interval [CI], 91.6%-100.0%). Among the 316 patients without PE, both D-dimer and dead-space results were normal in 163, for a specificity of 51.6% (95% CI, 46.1%-57.1%). Posterior probability of PE with normal results on both tests was 0.75% (95% CI, 0%-3.4%). CONCLUSION: In this multicenter study of ED patients, a normal D-dimer assay result plus a normal alveolar dead-space fraction was associated with a low prevalence of PE.
Asunto(s)
Productos de Degradación de Fibrina-Fibrinógeno/análisis , Sistemas de Atención de Punto , Embolia Pulmonar/diagnóstico , Pruebas de Función Respiratoria , Volumen de Ventilación Pulmonar , Adulto , Anciano , Servicio de Urgencia en Hospital , Femenino , Humanos , Funciones de Verosimilitud , Masculino , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Estudios Prospectivos , Alveolos Pulmonares , Sensibilidad y EspecificidadRESUMEN
In 1990, the multicenter Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED), sponsored by the National Institutes of Health, compared the diagnostic value of the radioisotopic ventilation-perfusion lung scan (V/Q scan) with that of pulmonary angiography for the diagnosis of pulmonary embolism (PE). Despite the endurance of the radioisotopic V/Q scan as the most widely used test for evaluation of pulmonary embolism (PE), a better screening tool is clearly needed for use in the emergency department. During the past decade, several new modalities have emerged for evaluation of patients with suspected PE. We evaluate the diagnostic utility of the D-dimer test and the alveolar dead space determination as potential screening tests and of spiral computed tomography, magnetic resonance imaging, transthoracic echocardiography, and transesophageal echocardiography as potential confirmatory tests for PE. For comparison, recent data on the diagnostic utility of the alveolar-arterial oxygen gradient and the V/Q scan are included. The potential application of these new tests to a hypothetical ED population is described.