Despite popular opinion CT pulmonary angiography has not emerged as the diagnostic modality of choice for PE. Finally, 16 years after PIOPED was reported in JAMA and 9 months after I posted the PIOPED II findings here PIOPED II is reported in NEJM.
Detailed findings, discussed in my earlier post, will not be repeated here. Suffice it to say that although CT is a useful addition to the diagnostic armamentarium it does not emerge as a clear cut stand alone modality of choice. Just as with V/Q scanning, the predictive power of CT is poor when test results are discordant with pre-test probability. A Bayesian approach using an integrated clinical algorithm is still the best method. There is a 17% false negative rate with CT. Fortunately small peripheral emboli, of questionable clinical significance, account for the majority of these false negatives. This is inferior to nuclear scanning which, if normal (as distinguished from “low probability”), demonstrated 100% sensitivity in PIOPED. Put another way, no patient in PIOPED with a normal perfusion scan had PE. Editorial comment in the same NEJM issue is here.