PURPOSE: CT pulmonary angiography (CTPA) is the preferred diagnostic modality for pulmonary embolism (PE) in many institutions. With no additional contrast, CT venography (CTV) can be used to detect deep vein thombosis (DVT). We hypothesized that the transition from nuclear lung scans (V/Q scan) to contrast CT scans increases the capacity to diagnose PE that otherwise might remain undetected.
METHODS: We retrospectively examined the records of all patients who were evaluated with either CTPA/CTV or V/Q scans at a University teaching Hospital, accumulating data only for the month of January from 1998-2007. Demographic and radiographic data were analyzed. All V/Q scans with indeterminate readings were independently reviewed by one of us (DK).
RESULTS: Over the past 10 years, the number of CTPA studies increased from 15 to 138 per month whereas the number of V/Q studies fell from 74 to 7 per month. The total number of PE diagnosed by either test progressively increased and was twice as large in Jan 2007 (20/month) as in Jan 1998 (10/month). During this same interval the diagnostic yield of CTPA remained relatively constant (11%±1, mean±SEM; range 7-18%).
CONCLUSION: We observed a trend to increased testing for suspected PE, primarily as a consequence of increased requests for CTPA/CTV. In 2007, the number of positive studies for PE and DVT doubled when compared with ten years earlier. One possible explanation is that the true incidence of VTE has increased. More likely, a combination of increased clinical suspicion plus the ready availability and enhanced quality of CT multidetector scanners has resulted in improved clinical detection of VTE.
CLINICAL IMPLICATIONS: While it is widely recognized that as many as 70-80% of cases of PE are undetected, the increased accuracy of CTPA/CTV compared with V/Q scanning may significantly improve the clinical detection of this treatable but potentially fatal disease.
DISCLOSURE: Adam Hurewitz, None.