Re: When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found
The principles presented are entirely correct, except the assertion that CT pulmonary angiography "is too good" is inaccurate. The authors contend that the test is exquisitely sensitive and detects small pulmonary emboli that may not be clinically relevant. Whilst this is true, a major confounder is simply that the test is not as accurate as it purports to be. This is evident by studies of inter-reporter variability showing a kappa of only 0.47 for 3mm CTPA [1]. Such modest agreement is not compatible with an accuracy of over 90-95% - if you show the same study to five radiologists, you might surprised at the different answers you receive. Many factors contribute such as respiratory motion and contrast artefacts. In the real world, many radiologists fear missing a PE resulting in high sensitivity reporting. This is not "too accurate" but "over-calling". There was never "small" PE to start with. A key strength of functional imaging such as V/Q scintigraphy has always been its ability to visualise the physiologic significance of PE.
[1] Chartrand-Lefebvre C et al, AJR Am J Roentgenol 1999; 172:107-112
Rapid Response:
Re: When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found
The principles presented are entirely correct, except the assertion that CT pulmonary angiography "is too good" is inaccurate. The authors contend that the test is exquisitely sensitive and detects small pulmonary emboli that may not be clinically relevant. Whilst this is true, a major confounder is simply that the test is not as accurate as it purports to be. This is evident by studies of inter-reporter variability showing a kappa of only 0.47 for 3mm CTPA [1]. Such modest agreement is not compatible with an accuracy of over 90-95% - if you show the same study to five radiologists, you might surprised at the different answers you receive. Many factors contribute such as respiratory motion and contrast artefacts. In the real world, many radiologists fear missing a PE resulting in high sensitivity reporting. This is not "too accurate" but "over-calling". There was never "small" PE to start with. A key strength of functional imaging such as V/Q scintigraphy has always been its ability to visualise the physiologic significance of PE.
[1] Chartrand-Lefebvre C et al, AJR Am J Roentgenol 1999; 172:107-112
Competing interests: No competing interests