False Positive
Jul 29th, 2009 by mark
The university here has been offering free hearing screenings this summer. I signed up and had one a month or so ago and the results confirmed what I had long suspected: I have a slight hearing loss in the higher frequencies. In addition to an audio test, the compliance of my ear drum was tested (measuring the pressure difference between my inner and outer ear), and a visual examination of my ear canal and ear drum was made. The visual inspection was done, in part, via a camera, so I got to see my ear on a small screen. Very cool.
The result of my test was “failed,” since I wasn’t able to hear the 4000 MHz range at normal speaking volume. The volume had to be increased from 25 decibels, to 35 before I could hear the highest pitched tones. The doctor recommended that I schedule a complete hearing test to determine what the underlying cause of this loss, and to establish a baseline for future hearing tests.
Since the screening was open to dependents and spouses, I signed Sibylle up for one too. She also has some hearing issues, primarily in her right ear. The result of her test was “passed.” Which wasn’t at all satisfying as she has real difficulty hearing with her right ear. On our way home from the exam we talked about the discrepancy between the test and her experience. In the end we figured out that the test was designed to measure only one axis of hearing. The truth is that Sibylle can hear the normal range of spoken frequencies at the normal volume of 25 decibels. However, the clarity of those sounds is muddy or muffled due to calcified fluid behind her ear drum.
The test produced a false positive, and a sense of frustration, since it only tested volume and range. Without a follow on test of clarity there is no way to draw a complete, or accurate, picture of her hearing. As an adult, who has lived with the hearing deficiency in her right year for most of her live, Sibylle has learned to compensate and adapt to her hearing perceptions. She can articulate what it is like, and could, I believe, successfully describe it to a doctor so that they could understand what she experiences.
But what if she were a child who was experiencing difficulty with the clarity of hearing? The screening as conducted would say to the child, and their parent or care-giver, that their hearing was perfectly normal when in fact it wasn’t. Imagine being that child, who knows that things sound funny, who can’t always understand what is said in a classroom, who complains that, “my ears feel like there’s cotton stuffed in them” – all to no avail because some 10 minute hearing screening showed that they could hear the normal frequencies at normal volumes.
I’m not saying that hearing screenings like the one that Sibylle and I participated in are without value, but I am saying that great care has to be taken in how they are framed. They should be described as a test of only hearing range, and not a test of clarity or comprehension. In a case like Sibylle’s, where the patient describes a long term situation that the test doesn’t provide corroboration for, additional tests or examinations should be undertaken. Looking at the results of a simple 5 minute test and saying that “your hearing is perfect” and discounting the patient’s described experience is a disservice.