With a suspected stroke, speed matters. If this device described in the release, called a volumetric impedance phase shift spectroscopy (VIPS), could help emergency personnel determine where to take patients with suspected stroke for treatment (a comprehensive stroke center or a primary stroke center) then it might be very valuable. The release describes a published study on the VIPS diagnostic tool showing that it can accurately detect large-vessel occlusion (a blockage or closing of a blood vessel) in patients with suspected stroke yet it misses some of the key features you’d expect with a news release talking about a new diagnostic tool, especially its cost, and its accuracy measured against other methods, such as a mobile CT scan, to differentiate strokes.
If care could be improved by a speedier, easy to use device which helps decide whether endovascular therapy (a procedure used to treat problems affecting the blood vessels) is necessary this could well improve outcomes for stroke patients. Researchers at the Medical University of South Carolina (MUSC), Mount Sinai, the University of Tennessee Health Sciences Center and elsewhere published a study in the Journal of Neurointerventional Surgery suggesting that their device (a visor worn by emergency personnel) called a volumetric impedance phase shift spectroscopy (VIPS) was better at identifying patients with large-vessel occlusions than a standard physical examination.
This matters because if the device passes all the other tests we expect of diagnostic tools including showing it’s sufficiently sensitive and specific and an improvement over other methods, then it could more quickly route patients to stroke centers that have endovascular capabilities and have a large impact on the outcome of patients.
Even though the device is still in its testing phase, not discussing what the ultimate cost could be does a disservice to readers.
It is important when discussing medical diagnosis to relate the test sensitivity (the ability of a test to correctly identify those with the disease or the true positive rate), and the test specificity (the ability of the test to correctly identify those without the disease or the true negative rate). This news release only mentions the specificity of the test, even though the actual study it was summarizing reports that “the VIPS device was able to differentiate severe stroke from minor strokes with a sensitivity of 93% (95% CI 83 to 98), specificity of 92% (95% CI 75 to 99)… and differentiate severe stroke from all other subjects with a sensitivity of 93% (95% CI 83 to 98), specificity of 87% (95% CI 81 to 92), and an AUC of 0.95 (95% CI 0.89 to 0.96).”
However, we should remember that diagnostic tests need to demonstrate that they offer a benefit beyond the current standard of care and that using them would improve patient outcomes. The current study doesn’t measure that and so it is hard to know if it will be helpful in treating patients.
There are no harms mentioned in this news release. One big concern with both diagnostic and screening tests is the consequence of a false negative test result which could lead to a patient receiving the wrong, unnecessary or no treatment.
The study compares this device to a standard clinical diagnosis. However, the gold standard in stroke care is a CT scan which determines if a patient is a candidate for clot busting drugs like tissue plasminogen activator (tPA), which opens blocked vessels after a stroke, or endovascular therapy. The real comparison would be comparing this device to CT scans given that mobile CT scanners are increasingly being used in ambulances.
The release doesn’t engage in disease-mongering.
The release identifies the funding company, Cerebrotech Medical Systems, and notes that Cerebrotech “paid consultants to analyze the neuroimaging data independently.”
The study compares this device to a clinical diagnosis by neurologists and the release states that the device showed “92 percent specificity” which we are told is above the “standard physical examination tools used by emergency personnel that display specificity scores between 40 and 89 percent.”
But as noted above, the better comparison would be comparing this device to CT scans given that mobile CT scanners are increasingly being used in ambulances.
We learn that this is very preliminary research and that the researchers will do another study to “determine if the VIPS device can use complex machine learning algorithms to teach itself how to discriminate between minor and severe stroke without the help of neurologists.”
The device itself is new technology so it earns a Satisfactory for the novelty claim.
However, the idea of pre-hospital diagnosis is not novel. Putting CT scanners in ambulances has been tried and seems to be (at least preliminarily) successful. This may be a low-cost alternative to that, but that still needs to be proven.
There is no inappropriate language used here, but there is a simile that might be suspect:
“This could potentially be something like a defibrillator,” said Turner. “You can find out if a patient is having a stroke, just like you can put a defibrillator on a patient to see if they’re having a heart attack.”
That comparison is fairly flawed. Monitors diagnose arrhythmias. ECGs diagnose heart attacks. Defibrillators shock patients who are having an arrhythmia during their heart attack.