D-dimer screening sporadic for PE evaluation in ER

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D-dimer screening is not used according to established diagnostic algorithms to determine the need for multidetector CT (MDCT) in diagnosing acute pulmonary embolism (PE) in emergency departments, based on findings of a single-center study published in the May issue of the American Journal of Roentgenology. Michael T. Corwin, MD, and colleagues from the Warren Alpert Medical School of Brown University and Rhode Island Hospital in Providence, R.I., sought to investigate whether D-dimer screening is being used effectively to determine the need for MDCT in diagnosing acute PE in emergency department patients.

The researchers performed a retrospective review of all patients who underwent D-dimer testing or MDCT in the emergency department from Jan. 1, 2003, through Oct. 31, 2005. A D-dimer value of > 0.43 µg/mL was considered positive. Diagnosis of PE was made on the basis of the MDCT. Clinical algorithms for diagnosing PE mandate that patients with a low clinical suspicion for PE undergo D-dimer testing, then MDCT if positive. For patients with a high clinical suspicion for PE, MDCT should be performed without D-dimer testing.

They performed a retrospective review of all patients who underwent D-dimer testing or MDCT in the emergency department from Jan. 1, 2003, through Oct. 31, 2005. They wrote that the D-dimer value of more than 0.43 µg/mL was considered positive. Diagnosis of PE was made on the basis of the MDCT. Clinical algorithms for diagnosing PE mandate that patients with a low clinical suspicion for PE undergo D-dimer testing, then MDCT if positive. For patients with a high clinical suspicion for PE, MDCT should be performed without D-dimer testing, according to the authors.

Of the 3,716 D-dimer tests, 39 percent were positive and 61 percent were negative. MDCT was performed in 7 percent of patients with negative D-dimer results and in 58 percent of patients with positive D-dimer results. The prevalence of PE in patients with a high clinical suspicion and no D-dimer testing was 9 percent, which was higher than the rate of PE in the positive D-dimer group at 2 percent.

The authors noted that there was no significant difference in the prevalence of PE in the positive and negative D-dimer groups (2 vs. 0.6 percent, respectively). The sensitivity and negative predictive value of D-dimer for PE were 95 percent and 99 percent, respectively.

Although previous studies using "rigid protocols have shown that such algorithms are effective in diagnosing or excluding PE, this is the largest study that evaluates whether physicians are actually using the algorithms in a busy academic emergency department," the authors noted. They wrote that during the study period, D-dimer screening was not used effectively to determine the need for MDCT in diagnosing acute PE in emergency patients.

Corwin and colleagues also concluded that because 42 percent of patients with a positive D-dimer who should have undergone CT did not receive the exam and 7 percent of patients with a negative D-dimer who should not have undergone CT according to protocol, actually did undergo CT. According to current diagnostic algorithms, all patients with a low clinical suspicion for PE who have a positive D-dimer should undergo MDCT. Forty-two percent of patients with a positive D-dimer did not undergo MDCT. "If we assume the same 2 percent prevalence of PE that was seen in the positive D-dimer patients who did undergo CT, then the diagnosis of acute PE was missed in 12 patients," the authors wrote.