APD Test Battery: Skill Driven

Question

Answer

While the client's complaints should be a consideration with respect to test selection, the nature of your test battery should be processing-skill driven, not complaint driven. For example, the client comes in complaining of difficulty hearing in noise. This non-specific complaint may be the result of any number of issues, including impaired auditory processing. If one selects several tests involving recognition in noise, all you really know when you're finished is what you knew before you started - that the client has trouble hearing in noise. However, you still don't know why. The complaints with which our clients come armed are only symptoms that something is wrong. As audiologists, our role is to evaluate auditory function in an effort to uncover the "why" behind those symptoms. Our clients don't need us to validate their listening complaints. They need us to help uncover the reasons for those listening difficulties, be they auditory-based or not.

Sometimes, ruling out a specific auditory processing deficit is just as useful as having ruled one in. So, how to accomplish that task? Make sure you probe all the possible skill sets that may be deficient. By "probe" I don't mean spend hours and hours on each set or run dozens of tests. Just make sure you've checked all aspects. As audiologists we do that regularly when it comes to peripheral hearing loss - never stopping at just puretone air conduction if those thresholds are off, but instead checking bone conduction, immittance, OAEs, etc. as needed to uncover the nature of the apparent hearing problem. The logic doesn't change just because we've crossed into the central auditory nervous system. Think "geographically" if you will - where along the pathway should I look and what skill or skills are subserved at that area? When looking at the system, one notes the need for a CAP evaluation battery to have tools to assess brainstem and cortical function, including interhemispheric connections.

The skills subserved by these regions include, as identified to date, binaural interaction (e.g., localization, binaural fusion, release from masking), binaural integration and separation (dichotic listening), temporal processing (temporal resolution, temporal patterning) and auditory discrimination and closure. Now, the sweet thing about CAP tests is that no one test taxes only one skill. Depending upon your choice of specific tests, you can "kill two birds with one stone" as it were. For example, temporal patterning tests (e.g., duration patterns, pitch patterns) will tax both temporal processing AND interhemispheric communication, especially if you ask the client to label the patterns. You also need to consider the age of your client base and have versions with age-appropriate vocabulary or you risk reducing reliability of your results.
Finally, the prudent move is to make sure you have some tasks with significantly less lingusitic load than others. For example, the SSW Test taxes dichotic listening but is fairly heavily loaded for language. Whereas, dichotic digits tests tax binaural integration (and separation, depending upon what you ask your client to do) with much less language load as numbers are inherently easier to process than random words.

The one thing you want to avoid is using a "cookbook" to assess. That is, falling into the trap of believing that there's some one ideal test battery out there that will meet all of your assessment needs. In a perfect world, maybe, but... For what it's worth, I have some three dozen CAP tests in my assessment arsenal- all makes and models at-the-ready to accommodate whomever may walk through the door, complaint-wise OR patient-variable-wise. The evaluation process should probe auditory function PANS through CANS, providing sufficient information a) to make an informed differential diagnosis, b) to discuss with the client the nature and impact of any identified auditory deficit, c) to develop a deficit-specific intervention plan, and d) to make referrals to other professionals as needed. Exactly which tests should one have on hand or use with which clients depends upon the audiologist's knowledge and training with respect to CAPD and the clients' needs. Professional working groups of both ASHA and AAA have taken up this question and many other issues related to CAPD assessment and management. Check out either organization's website for more information.

Jeanane M. Ferre, Ph.D., Audiologist, CCC-A.
Fellow of American Speech-Language-Hearing Association
Central Auditory Evaluation and Treatment
Oak Park, IL