Diagnostic accuracy of a bedside D-dimer assay and alveolar dead-space measurement for rapid exclusion of pulmonary embolism: a multicenter study.
BACKGROUND
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.


METHODS
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.


METHODS
Six urban teaching hospitals in the United States.


METHODS
A total of 380 hemodynamically stable ED patients aged 18 years or older with suspected acute PE.


METHODS
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%).


CONCLUSIONS
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.
Kline
J A
JA
Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC 28232-2816, USA. jkline@carolinas.org
Israel
E G
EG
Michelson
E A
EA
O'Neil
B J
BJ
Plewa
M C
MC
Portelli
D C
DC
D000328:Adult; D000368:Aged; D004636:Emergency Service, Hospital; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011650:Pulmonary Alveoli; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D013990:Tidal Volume
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D