Results of ventilation-perfusion scans: Emergency department patients with and without risk factors

Abstract

We prospectively studied 141 of 143 consecutive patients over a 6-month period referred for a ventilation-perfusion ($\dot V/\dot Q$) scan from the emergency department of an 800-bed university-affiliated teaching hospital. Numerous clinical, laboratory, and radiographic data were analyzed. Our hypothesis was that performing a$\dot V/\dot Q$scan in a patient without a risk factor for pulmonary embolus (PE) is of little value.

Of the 141 patients, 81 (57%) had no known risk factors for PE, and 60 (43%) had one or more risk factors for PE. Of those patients without risk factors, none had a highprobability scan, one patient (1%) had an intermediate-probability scan, 49 (61%) had a low-probability scan, and 31 (38%) had a very-low probability or normal scan. Of those patients with risk factors, nine (15%) had a high-probability scan, seven (12%) had an intermediate-probability scan, 26 (43%) had a low-probability scan, 17 (28%) had a very-low-probability or normal scan, and one (2%) had evidence of unchanged chronic PE. Risk factors and$\dot V/\dot Q$ scan interpretations are significantly related.

Eleven (8%) of the 141 patients were discharged with a diagnosis of PE. All of these patients had at least one risk factor for PE. Risk factors were the only discriminating criteria for PE in our patient population. Although a small study such as ours cannot be used to make broad decisions on$\dot V/\dot Q$ scan ordering practices, our findings suggest that ordering a$\dot V/\dot Q$ scan in a patient without a risk factor for PE is of little value.