DIAGNOSTIC
ACCURACY OF A BEDSIDE D-DIMER ASSAY AND ALVEOLAR DEAD-SPACE MEASUREMENT FOR
RAPID EXCLUSION OF PULMONARY EMBOLISM: A MULTICENTER STUDY.
Kline
JA, et al. JAMA 2001 Feb 14;285(6):761-8.
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.