Stenger Test and Patient response monitoring with KUDUwave
While the general population are unlikely to attempt to malinger or exaggerate their hearing loss, the prevalence of nonorganic hearing loss (NOHL) is much higher when secondary gains are expected. For example, much research has reported a higher prevalence of audiometry malingering in industrial workers and military personnel.
Non-organic hearing loss (NOHL), also known as functional hearing loss or pseudohypacusis, is a condition in which there is an apparent hearing loss with no evidence of a known disorder or insufficient audiological information to explain the loss.
In occupational healthcare or industrial healthcare, incidences where normal hearing workers consciously feign a hearing loss is relatively common.
It is often difficult for testers or practitioners without an audiology background and training to identify individuals who may be faking their hearing loss.
This is the reason I have decided to write this article, and share some of the KUDUwave features that can help testers to identify malingerers in their setting.
Determining the actual hearing threshold is crucial in industrial health / occupational health. However, amongst individuals who may be faking their hearing loss, diagnosing NOHL is time and energy-consuming
This diagnosis also requires good clinical skills that many who are not trained audiologists may not have. Inaccurate determination of hearing levels (thresholds) may result in incorrect compensation towards the employee.
Recently, I wrote about how to catch a malingering patient when patients undergo audiometry testing, the article covered some of the reasons a patient might malinger. This article will focus specifically on the utility of the KUDUwave audiometer features’ for the evaluation of nonorganic hearing loss. The KUDUwave has tests and features that will assist greatly in evaluating and diagnosing NOHL.
These are the Stenger test and patient response statistics.
Stenger test with the KUDUwave
The Stenger test has been utilized in the field of audiology for many years as it is one of the most powerful tests for evaluating and diagnosing NOHL. The Stenger test is based on the ‘Stenger principle’, which states that when two tones of the same frequency are introduced into both ears at the same time, only the louder of the two tones will be perceived by the subject.
This test should be used if a subject presents with unilateral hearing loss (hearing loss in one ear) and the tester suspects that they may be faking it. In addition, if there is a significant asymmetry between the ears of at least 20 dB, this test can also be used.
How do you use it with the KUDUwave
Ensure that a full pure tone audiometry test has been conducted before utilizing the Stenger Test. Get air conduction thresholds for both ears, as indicated in the example below.
It is important to ensure that the instructions to the patient do not differ from those you would give with normal audiometric testing – i.e. the patient should not be informed that the tone will be presented in both ears simultaneously.
Once you have acquired thresholds for both ears, press the ‘Stenger’ button on the right-side panel of your test screen to begin. The Stenger test is set to present tones in both ears at the same time when ‘Stenger’ is selected.
At the desired frequency (i.e. 1 kHz), the tone intensity in the better ear will be set at a level 10 dB above the threshold (note that this is default, but can be modified under settinga test macro) – the 10 dB above threshold is indicated by the block icon on the test screen.
In the poorer ear, set the intensity at a level 10 dB below the admitted threshold.
When ready, press the shift key on your keyboard to present the tone in both ears. Keep the intensities in both ears fixed. If the subject’s hearing loss in the worse ear is genuine, the subject will not be aware of the tone in the worse ear, and will respond to the tone in the better (or good ear) readily – because of the 10 dB above the threshold, it should be clearly audible. Such a response is called negative stenger, indicating that the poorer ear threshold is probably correct.
If the subject does not admit hearing in the worse ear and is unaware of the tone in the good ear, they will not respond. This is called positive Stenger. This proves that the threshold from the poorer ear is better than the admitted thresholds by the patient.
The test described above is a quick screening procedure that identifies the presence or absence of unilateral nonorganic hearing loss. A positive Stenger does not identify the true organic hearing threshold/s. To obtain threshold information, the Stenger test can also be performed by seeking the minimum contralateral interference levels (MCIL).
Present a 10 dB SL (10 dB above the threshold) tone in the good ear. There should be a response from the patient to indicate that this is audible.
A tone is then presented from 0 dB HL in the bad ear, simultaneously with the tone at 10 dB above the threshold in the good ear. If a response is obtained, the level is raised 5 dB above the bad ear, keeping the level in the good ear fixed. The level is continuously raised in 5 dB steps until the subject fails to respond.
Because the tone in the good ear is still 10 dB above the threshold, the lack of response must mean that the tone in the bad ear is loud enough (and that the subject hears it) and is experiencing the Stenger effect, and is no longer aware of the tone in the good ear.
Being unwilling to react to the tone heard in the bad ear, the subject simply stops responding.
As soon as the subject stops responding, that level is called MCIL and is the true threshold, which is within 20 dB of that level. This is often plotted 20 dB below the actual threshold.
Patient response monitoring with the KUDUwave
This is a simple way of evaluating whether your patient’s threshold or responses are accurate. The KUDUwave counts the amount of time the response button is clicked during a hearing test and automatically determines which of the clicks are false positive or true positive responses.
This is where a response button is of significant advantage compared to having your patient raise their hand during audiometry testing.
While the Stenger test on the KUDUwave works really well, patient response statistics is my favourite feature as the audiometer does all the work for you.
As the tester, your job will be analyzing the response data and making an informed decision on whether to accept the patient thresholds or to retest. This information is found at the bottom of the audiogram once testing is complete and results saved. Let’s look at what the data means below.
The test-retest reliability looks at the correlation between two responses/ hearing thresholds at 1000 Hz. During automated audiometry (this is recommended with manual audiometry too), 1000 Hz is tested both in the beginning and at the end of the test- the two thresholds obtained at that frequency should be within 10 dB of each other.
This indicates the reliability and response consistency from your patient.
Would it not be suspicious if a patient responds at 10 dB the first time then 50 dB the second time, at the same frequency?
Thus, the test-retest reliability score on the patient audiogram should not be more than 10 dB.
The false-positive response indicates the number of times a patient pressed the response button with no tone being presented. A patient should only press the button when they hear a tone. False-positive responses are shown as a percentage.
At times, this may indicate that the patient clearly did not understand the test instructions, as they would be responding at all time regardless of whether the tone is presented or not. A tester might need to re-explain what is required of the patient.
On the other hand, a high false-positive response percentage may suggest that the patient is malingering (or faking their hearing thresholds). In conclusion, the false-positive response should not be higher than 10%. However, as a tester, you may decide to accept these test results (even with higher false-positives) with a good clinical explanation.
The standard deviation, in this case, monitors the patient’s response time after every tone presented. That response time is averaged, and if the time to respond to a tone deviates more than 300 milliseconds, then this could indicate that the patient is potentially malingering.
Subjects are generally consistent with their response time throughout the testing period.
In the majority of cases, the detection and identification of NOHL is not a difficult task for a trained and alert clinician. It is more challenging when the tester does mass hearing tests, this often results in the use of automated audiometry in order to save time and get through every patient.
The challenge is further aggravated by the lack of objective test devices like otoacoustic emission (OAE) provided in occupational health services for audiometric screening to confirm subjective hearing thresholds or apparent thresholds.
The Stenger test and patient response statistics on the KUDUwave are quicker and easy to perform and interpret. Therefore, we encourage people to use these methods when suspecting anyone of faking a hearing test in their audiometric health assessments.
Here is how to do it in the KUDUwave Software
These methods come standard with all the KUDUwave devices, of different configurations – make use of them!
Lastly, as stated in the previous article, how to catch a malingering patient, great care must be taken when dealing with and writing reports about patients with suspected NOHL.
Bear in mind that once an individual has been diagnosed or labelled as “malingering”, their reputation may be damaged. Labelling a patient that way is a significantly grave matter as it implies deliberate falsification.
Remember, malingering can be caused by many factors, not just financial gain, to have a look at other factors that may result in a patient malingering and how to deal with such patients, please read how to catch a malingering patient.