The Diagnostic Values of D-Dimer and Alveolar-Arterial Gradient Tests in Diagnosis and One-Month Status of Patients with Dyspnea

Some of studies have shown that measurement of some laboratory parameters such as D-dimer and arterial blood gases can be helpful in the diagnosis of pulmonary embolism. This study aimed to determine the diagnostic values of D-dimer and alveolar-arterial gradient (A–a gradient) for detection of pulmonary embolism in patients with shortness of breath.

In a descriptive-analytical study, 196 patients with symptoms of shortness of breath referred to the emergency departments of Alzahra and Ayatollah Kashani hospitals in Isfahan City, Iran, were studied, and their D-dimer and arterial blood gas levels and A-a gradient were measured. All patients underwent CT scan of the lungs, and the presence of pulmonary embolism was evaluated. The diagnostic value criteria of the two tests including sensitivity, specificity, and positive and negative predictive values were evaluated in comparison with CT scan.

Sensitivity, specificity, and positive and negative predictive value were obtained 70.41, 94.79, 93.20, and 75.80 percent for the D-dimer test, respectively, and 92.7, 17.24, 55.3, and 68.2 percent for the A–a gradient test, respectively. The area under the rock curve of receiver operating characteristic (ROC) was 0.85 (P < 0.001) for the D-dimer and 0.5 (P = 0.820) for the A-a gradient.

The D-dimer test has high diagnostic value criteria for diagnosis of pulmonary embolism in patients with symptoms of shortness of breath, while parameters related to arterial blood gases such as A-a gradient do not have high diagnostic values to diagnose this complication.