Friday, October 15, 2010

Brain Trauma Blood Test Shows Promise But Report of Findings Is Flawed

USA Today reports that US Army doctors have discovered a blood test that can reveal whether a trauma victim has had a concussion. The test measures the level of proteins released when brain cells are damaged. If these findings are confirmed in a larger study, it would be a major advance in the treatment of traumatic brain injury [TBI]. However, the article is mostly an uncritical look at the subject.

A major question not answered is how was the blood test validated? A quote from the report “Doctors can miss these injuries because the damage does not show up on imaging scans…” is correct, but how then did they verify that a patient with a positive blood test indeed had a concussion? In medicine, before a new diagnostic test can be accepted for general use, it must be compared to a so-called “gold standard.” If the new blood test was not measured against the results of head CT scanning, then what was the gold standard used?

Only 34 subjects were included in this apparent pilot study, which has not been subjected to the peer review process. I would like to call the new blood test by the name of the protein or proteins being investigated, but the article did not provide that information.

The article referred (without a link) to a Rand Corporation study that, according to the USA Today article, stated “About 300,000 troops in Iraq and Afghanistan have suffered concussions…” I accessed that study and found that what it actually said was

“A telephone study of 1,965 previously deployed individuals sampled from 24 geographic areas [found that] 19 percent reported a probable [emphasis added] TBI during deployment...”

The author of the USA Today piece apparently then assumed that 300,000 or 19% of the 1.64 million deployed troops had in fact experienced concussions, a rather large leap of faith on three levels. The following assumptions are invalid: one, a “probable” TBI is the same as an actual concussion; two, a telephone interview is an accurate way to acquire clinical information; three, the results of a telephone sample of 1,965 people, which is 0.1% of those deployed, can be extrapolated to represent the experience of the entire population of troops.

A larger study of the unnamed protein is planned. Let’s hope it does prove to be an effective test. As the article points out, a TBI blood test would be useful in many areas such as sports, child abuse and others.

No comments:

Post a Comment