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Abstract
The diagnosis of a Pulmonary Embolism (PE) is a challenging clinical problem, our approach to which has changed greatly since the introduction of Computed tomographic pulmonary angiography (CTPA). CTPA is now established as the imaging modality of choice for the diagnosis of PE, however there are concerns that CTPA causes the over-diagnosis of clinically irrelevant PE,1,2 and there is little data concerning the outcomes and further imaging following a CTPA at long follow-up times. Here we present long term follow-up of CTPAs over 5 years, looking at further imaging related to suspected thromboembolic disease after more than 2000 studies. After their initial CTPA, further studies were documented retrospectively using electronic patient records. Figure 1 demonstrates what further imaging for suspected venous thromboembolic event (VTE) patients had following their CTPAs scans over 5 years. In a one-year period, 24% of the negative studies, 38% of the positive, and 50% of the indeterminate studies had repeat testing for suspected thromboembolic disease. Indeterminate studies received repeat testing faster (p<0.001), and those with negative studies received fewer repeat tests (p<0. 001). Those with a positive initial result were more likely to have positive recurrent testing over the whole 5 year period, and these data also suggest a trend showing increased risk with positive PEs rather than other VTEs. Furthermore, although CTPAs had a very high calculated negative predictive value for excluding PE (over 99%), many patients went on to have repeat testing following a negative result. Understanding how test Results influence the predictive value of further testing is essential for effective risk stratification, and this work adds to the growing body of data examining the long-term implications of a CTPA result.
References
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