Medicine, like life, is full of uncertainty. Every action or inaction has costs and consequences, both anticipated and unintended. Permeating through medical culture for many reasons, with the proliferation of tests available, has been a decreased tolerance for this uncertainty and the rise of “zero-miss” medicine. However, there are some tests that carry with them enough cost and risk, the population harms of the test outweigh the harms of the missed diagnoses. CTPA for pulmonary embolism is one of those tests.
In this study, these authors attempt to reduce testing for pulmonary embolism by creating a shared decision-making framework to discuss the necessity of testing with patients. They prospectively enrolled 203 patients presenting to the Emergency Department with dyspnea and, independent of their actual medical evaluation, attempted to ascertain their hypothetical actions were they to be evaluated for PE. Specifically, they were interested in the “low clinical probability” population whose d-Dimer was elevated above the abnormal threshold – but still below twice-normal the threshold. For these “borderline” abnormal d-Dimers, the authors created a visual decision tool describing their estimate of the benefit and risk of undergoing CTPA given this specific clinical scenario.
After viewing the benefits and risks of CTPA, 36% of patients in this study stated they would hypothetically decline testing for PE. Most of the patients (85%) who planned to follow-through with the CTPA did so because they were concerned regarding a possible missed diagnosis of PE, while the remaining hoped the CT would at least also provide additional information regarding their actual diagnosis. The authors conclude, based on a base case of 2.6 million possible PE evaluations annually, this strategy might save 100,000 CTPAs.
I think the approach these authors promote is generally on the right track. The challenge, however, is the data used to discuss risks with patients. From their information graphics, the risks of CTPA – cancer, IV contrast reaction, kidney injury and false positives – are all fair to include, but can be argued greatly regarding their clinical relevance. Is a transient 25% increase in serum creatinine in a young, healthy person clinically significant? Is it the same as a cancer diagnosis? Is it enough to mention there are false-positives from the CTPA without mentioning the risk of having a severe bleeding event from anticoagulation? Then, in their risk of not having the CTPA information graphic, they devote the bulk of that risk to a 15% chance of the CT identifying a diagnosis that would have otherwise been missed. I think that significantly overstates the number of additional, clinically important findings requiring urgent treatment that might be identified. Finally, the risks presented are for the “average” patient – and may be entirely inaccurate across the heterogenous population presenting for dyspnea.
But, any quibbles over the information graphic, limitations, and magnitude of effect are outweighed by the importance of advancing this approach in our practice. Paternalism is dead, and new tools for communicating with patients will be critical to the future of medicine.
“Patient preferences for testing for pulmonary embolism in the ED using a shared decision-making model”
http://www.ncbi.nlm.nih.gov/pubmed/24370071