May 10, 2011
Screening Tool Appears To Increase Pulmonary Embolism Diagnosis Rate; No Decrease In Related Deaths
The introduction of multidetector row computed tomographic pulmonary angiography (CTPA) was associated with an apparent increase in the diagnosis of pulmonary embolism (PE), but with only minimal changes in mortality (death), suggesting the possibility of overdiagnosis, according to a report in the May 9 issue of Archives of Internal Medicine, one of the JAMA/Archives journals. This article is part of the Less Is More series in the journal.
Pulmonary embolism usually occurs when a blood clot blocks a blood vessel in the lungs. If not treated, PE can be fatal. Therefore, the introduction of CTPA in 1998 was welcomed, the authors write: "Many assumed this highly sensitive test would improve outcomes of this deadly disease by detecting and allowing treatment of emboli that were previously missed." Since its introduction, the test has been rapidly adopted by clinicians as the first-line screen for PE.
"However, the increased sensitivity of CTPA may have a downside," explains Renda Soylemez Wiener, M.D., M.P.H., from Boston University School of Medicine and colleagues. The problem is "the detection of emboli that are so small as to be clinically insignificant" and unlikely to cause harm. The authors add, "treating such an embolism can cause harm (e.g., bleeding from anticoagulation, which can in the worst case be fatal)."
The researchers examined PE hospitalization rates from the Nationwide Inpatient Sample and Multiple Cause-of-Death files from the National Center for Health Statistics. They analyzed data for the incidence of PE and death from it, as well as in-hospital deaths among patients with the condition and complications from treating it. "If increasing use of CTPA was improving our ability to find and successfully treat clinically important pulmonary emboli, we would expect to see an increase in incidence "¦ and a reduction of mortality," the authors state.
An increase in incidence was observed, from about 62 cases per 100,000 U.S. adults before the introduction of CTPA in 1998 to about 112 cases per 100,000 U.S. adults afterward, an increase of 81 percent. Mortality rates from PE after 1998 have only decreased 3 percent (from 12.3 to 11.9 per 100,000 population), however. During this same period, case-fatality rates (the proportion of in-hospital deaths among patients with a PE diagnosis) decreased by 36 percent (from 12.1 percent to 7.8 percent) and in-hospital complications assumed to be from anticoagulant therapy increased by 71 percent (from 3.1 to 5.3 per 100,000 population).
"Rather than an epidemic of disease," the authors write, "we think the increased incidence of PE reflects an epidemic of diagnostic testing that has created overdiagnosis." That is, more emboli have been found through CTPA, but not all of those emboli would eventually cause harm to patients; and some may be false-positives. Even among the results that are true-positives, "overdiagnosis of these extra patients matters because treatment of PE can cause real harm," the authors caution. They conclude with a call for a randomized study of stable patients to evaluate the effects of observation versus anticoagulation in the treatment of small emboli, to determine if intervention is always needed.
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