The shift from V/Q scintigraphy to CT angiography in the diagnosis of pulmonary embolism (PE) has been tied to an increase in incidence of PE, but not a decline in mortality, according to a study published in the June issue of American Journal of Roentgenology. The findings suggest the possibility of overdiagnosis.
More than one decade ago, pulmonary CTA, which provides improved visualization of pulmonary vasculature, emerged as an alternative to V/Q scintigraphy. Despite the advantage of improved visualization, previous studies have not determined that CTA reduces mortality.
Steven H. Sheh, MD, from the department of radiology at Montefiore Medical Center in New York City, and colleagues designed a two-part retrospective analysis to determine if CTA-diagnosed PE represents a milder disease spectrum than PE diagnosed by the earlier method. They also analyzed trends in incidence and mortality and correlated those with imaging modality trends.
The researchers analyzed data from 2,087 patients admitted to Montefiore with a diagnosis of PE from Jan. 1, 2000, to Dec. 31, 2007. The cohort included 1,361 women and 726 men (mean age, 61.8 years).
The rate of PE diagnosis increased significantly from 0.69 to 0.91 per 100 admissions during the study period, Sheh et al reported. Forty percent of patients were diagnosed with CTA, 23 percent with V/Q scintigraphy, 12 percent with both modalities and 26 percent with neither modality.
The use of scintigraphy declined over the study period, and the researchers observed a strong link between trends in PE incidence and CTA use. Neither seven- or 14-day mortality changed significantly during the study period, but the case-fatality rate dropped from 5.7 percent in 2000 to 3.3 percent in 2007.
“The results of the current study support the hypothesis that PE diagnosed with pulmonary CTA has a different, more benign natural history than PE diagnosed with V/Q scintigraphy and that overdiagnosis of clinically unimportant disease may be occurring,” wrote Sheh and colleagues.
The researchers noted that treatment for PE shifted to low-molecular weight heparin in the late 1990s, but studies have shown that low-molecular-weight heparin does not reduce mortality compared with standard heparin. Thus, reduced mortality should not be attributed to changes in patient treatment, according to Sheh and colleagues.
There were several limitations to the study, wrote Sheh et al, which included its retrospective design and lack of randomization of the comparison groups.
The authors concluded with a call for additional research. Specifically, they suggested outcome-based clinical trials with long-term follow-up, including an analysis of the effect of the diagnostic modality on treatment and complications.