CT pulmonary angiography and overdiagnosis of PE

A new study published in Archives of Internal Medicine looked at changing trends in diagnosis and outcomes for pulmonary embolism since introduction of CT pulmonary angiography:

We compared age-adjusted incidence, mortality, and treatment complications (in-hospital gastrointestinal tract or intracranial hemorrhage or secondary thrombocytopenia) of PE among US adults before (1993-1998) and after (1998-2006) CTPA was introduced. 

Results Pulmonary embolism incidence was unchanged before CTPA (P = .64) but increased substantially after CTPA (81% increase, from 62.1 to 112.3 per 100 000; P less than .001). Pulmonary embolism mortality decreased during both periods: more so before CTPA (8% reduction, from 13.4 to 12.3 per 100 000; P less than .001) than after (3% reduction, from 12.3 to 11.9 per 100 000; P = .02). Case fatality improved slightly before (8% decrease, from 13.2% to 12.1%; P = .02) and substantially after CTPA (36% decrease, from 12.1% to 7.8%; P less than .001). Meanwhile, CTPA was associated with an increase in presumed complications of anticoagulation for PE: before CTPA, the complication rate was stable (P = .24), but after it increased by 71% (from 3.1 to 5.3 per 100 000; P less than .001).

The authors note that these findings suggest overdiagnosis attributable to CTPA due to detection of isolated inconsequential filling defects. As the data show, this has significant clinical consequences. In that sense CTPA may be considered by some to be more sensitive than V/Q scanning. However, when long term clinical outcomes are used as the standard V/Q scanning has demonstrated superior sensitivity so long as a normal perfusion scan (note that’s normal, not “low prob”) is used to rule out PE.