How do we test for and diagnose Central Auditory Processing Disorder?
It is broadly recognised that the identification and management of CAPD is a multidisciplinary approach. Audiologists provide pivotal information for initial or differential diagnosis and assessment for auditory processing disorders. This may involve other health professionals such as speech pathologists, psychologists, and paediatricians if we are providing rehabilitation for children.
A comprehensive test battery is designed to minimise language and cognitive components so a more reliable picture of auditory processing skills can be obtained. Our CAP test battery follows the latest guidelines from Independent Audiologists Australia (IAA), in order to obtain a comprehensive assessment of different auditory processing skills and discern different types of CAPD.
Testing is conducted over 2 sessions within the same week, involving:
Comprehensive hearing assessment: the first session involves testing peripheral hearing function. We ascertain auditory function up to the level of the inner ear, through a series of tests:
- Tympanometry and acoustic reflex testing – these tests assess middle ear function, detecting the presence of issues such as ear infections or Eustachian tube dysfunction. They supplement further testing conducted to obtain hearing thresholds.
- Pure tone audiometry (PTA) – the key test to ascertain the hearing thresholds of an individual. It allows us to determine the degree, type, and configuration of a hearing loss.
- Speech audiometry – this test assesses the speech reception of an individual in ideal listening environments.
- Otoacoustic emissions (OAE’s) – this is an objective measure of auditory function up to the level of the inner ear. It consolidates information from other tests in the assessment, complementing behavioural tests such as PTA and speech audiometry.
CAP assessment: the second session involves a range of assessments targeting different auditory processing skills. Our CAP test battery includes:
- Quick Speech in Noise (QuickSIN) – an adaptive, virtual-reality test measuring how well you can understand speech in noisy environments (e.g. noisy classrooms, busy restaurants).
- Test of Auditory Processing Skills (TAPS3) – a series of tests assessing auditory memory skills, which are vital for listening, processing, storing, and recalling verbal information. These tests help to interpret results from further auditory processing tests in the battery, in order to distinguish between working memory issues or auditory processing issues.
- Low-pass Filtered Words – an auditory processing test that degrades and filters speech at 1000Hz. It assesses auditory closure skills – as it requires you to ‘fill in’ missing information to comprehend the whole word. It involves top-down processing and compensatory skills for missing acoustic details, such as in conversations in suboptimal listening environments.
- Dichotic Digits (DD) – involves presenting different information in both ears simultaneously, in order to assess binaural integration skills. It tests how well both ears work together to process and comprehend verbal information.
- Frequency Pattern (FP) – presents auditory sequences of sounds, assessing how effectively temporal patterns are processed. We assess the potential for language processing deficits as well, as interhemispheric transfer of information is required in a portion of the test.
- Listening in Spatialised Noise – Sentences (LiSN-S) – an adaptive test simulating a three-dimensional auditory environment, assessing how well you can process and distinguish speech from different directions. It involves a target speaker in the presence of competing noise from different directions, which evaluates spatial processing skills.
Why do we test across 2 sessions?
Difficulties hearing in background noise may be associated with the presence of a hearing loss, not necessary an auditory processing deficit. In order to accurately determine the presence of CAPD, we must first rule out the involvement of a peripheral hearing loss. Particularly in children, ear infections and other recurrent issues can lead to fluctuating hearing loss, which can adversely effect their listening skills in complex environments.
Therefore, the first session is a comprehensive hearing assessment to determine hearing thresholds and any issues with how well our ears can hear the sound. If our ears can’t hear the sound properly, our brain can’t receive the correct signals to process and interpret. This assessment takes up to 45 minutes to complete.
Once we affirm the absence of any peripheral hearing issues, we can proceed with testing auditory processing skills. Testing is conducted in the same week to eliminate any potential issues that may arise between the first and second session. This allows us to isolate the presence of a potential CAPD.
The second session of our full CAP battery is longer, taking up to 1.5 hours to complete. This can be quite demanding on children, although breaks can be taken throughout the session to ensure optimal attention and performance.
Why is there a minimum age for testing?
The minimum age for CAPD testing is 7 years, although it is advisable for the child to be 8 years or older. All the normative data (the information that we compare the child’s results against saying if this is normal or not) is based on age. There is no normative data for those under the age of 7 due to unreliability in testing.
Testing can be quite draining for children as it requires a significant amount of attention. Most children under 7 years are unable to maintain focus and/or unable to fully comprehend the tests accurately. Additionally, although 7 years is the minimum age for testing, every child develops differently and individual maturity levels may affect the interpretation and reliability of results.
Once results are obtained, a multi-disciplinary approach is taken to provide guidance for effective remediation strategies and rule out any other factors such as language impairment issues, cognitive problems, or attention difficulties.
Tips for testing:
- Ensure the child has not had any recent illnesses, such as a cold or ear infection. If an outer/middle ear issue or hearing loss is detected during the first session, the hearing assessment will need to be repeated at a later date before proceeding with CAP testing. This ensures that performance across the CAP test battery is an accurate representation of auditory processing skills, rather than issues with peripheral hearing that need to be addressed first.
- Rest well and have a big breakfast! Ensure you are well-prepared and your concentration will not affect performance on the various tests. We can take breaks as needed throughout the assessment, but set yourself up as optimally as possible.
- Get comfortable with wearing headphones – many children are not used to wearing headphones and doing different activities, but the assessment involves wearing headphones for an extended time. Ensuring you are comfortable helps with staying focused and reducing how demanding the testing can be for the child.
Next Steps: Booking in an assessment
If you, or your child’s teachers suspect a potential CAP issue, now is the time to book in an assessment.
Read more about the process for booking in an assessment.
Call 1300 252 748 or request a callback today.
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