4/3/2008

Neuropsychological Assessment: Flexible or Fixed?

Discover your best option for the most valid results

By Steven Carter, PsyD, LP

Evidence from neuropsychological assessments is commonly offered as proof of damage in insurance claims, yet many claims professionals have little or no understanding of neuropsychology and are left at a disadvantage when attempting to negotiate an equitable settlement. Here we’ll take a look at a basic overview of neuropsychology, review the shortcomings of the most commonly used neuropsychological assessment approach, and review new means of assessment that overcome most of those weaknesses.

 

What is neuropsychology assessment?
A neuropsychological assessment is the systematic administration of clearly defined procedures (i.e., “tests”) to a claimant suspected of functional impairments due to brain injury or disease. The specific tests are chosen because research has shown that a person’s performance on them is associated with a particular brain structure or pathway. Statistically comparing the claimant’s scores with those of healthy persons and those known to have specific brain injuries and diseases allows the neuropsychologist to determine the likelihood that the claimant is exhibiting signs of a specific brain injury or disease.

 

What do neuropsychological tests measure?
The most commonly assessed brain-behavior functions are attention, language, memory, spatial perceptual reasoning and executive functioning. The idea that these specific domains are dependant upon one another is known as the hierarchical model of neuropsychological functions. It recognizes attention as a basic function that underlies nearly all other domains of neuropsychological functioning.

 

Attention refers to the claimant’s attentional capacity, working memory, selective attention, divided attention and mental speed. If these fundamental abilities are impaired, then the claimant usually will have limited functional abilities at the higher levels in the model.

 

Language refers to receptive and expressive skills for oral and written information and word finding.

 

Spatial functioning refers to the skills necessary for a claimant to remain orientated geographically, judge angles and distances, attend to visual details, assemble pieces into a whole object and draw.

 

Memory refers to a claimant’s ability to remember things heard and seen both immediately after presentation and after a delay. A claimant with memory impairment can often perform attention, language, and spatial tasks well, but the converse is not true. In order to remember something, a claimant must first attend to it and then have adequate language skills to encode verbal information and adequate spatial skills for visual learning tasks.

 

Executive functioning refers to the skills of self-monitoring, self-correcting, planning, sequencing, prioritizing, judging, inhibiting and initiating one’s activities. These skills are necessary for success in a complex social environment.

 

Flexible approach, flexible results
In a clinical setting, a flexible battery of neuropsychological tests is often used. A flexible battery involves the selection and administration of an array of tests (i.e., the “battery”) that are based on the neuropsychologist’s perception of the patient’s presenting complaints. There is no one flexible battery shared by all neuropsychologists. The same neuropsychologist may use different combinations of tests with different patients, or even a different combination of tests with the same patient at different assessments when repeated assessments are performed. These neuropsychologists are essentially inventing their own idiosyncratic test batteries with each administration, and are hoping that the fact that each of the individual tests, which are valid to some degree, will somehow make the entire set of tests sensitive to brain damage and specific for the kind of brain damage that is allegedly present.

 

Problems with a flexible battery in forensic context
  1. Different assessment procedures for nearly every patient.
  2. Different assessment procedures across different examiners.
  3. Nearly impossible to scientifically validate for sensitivity and specificity.
  4. Extremely limited scientific evidence for its use.
  5. Open to examiner bias in method selection rather than demonstrated accuracy.
  6. Test selection is made based on subjective complaints that may arise from reasons other than brain injury.
  7. The value of the neuropsychological examination depends on the validity of the patient complaints.
  8. The meaning of differences and patterns of differences between tests cannot be known because the combination of tests administered is changed with each administration.
  9. The breadth of the examination is limited to suspicions about problem areas rather than a comprehensive assessment of the patient’s brain-behavior abilities.
  10. Scores between tests are not directly comparable because norms were taken from a wide variety of samples, situations and dates. Differences found may simply represent differences in the normative samples.
  11. No overall impairment index or rating is available for the battery tests used.
  12. The range of scores seen for normal or intact patients is unknown for the battery of tests used.

 

There is little data available to guide the clinician’s choice of tests when assembling a flexible battery. Personal preference, economic factors, availability of certain tests in the clinic, marketing by the testing companies and other unscientific sources of examiner bias often dictate test selection. The combination of tests selected may overemphasize areas of impairment and underemphasize areas of strength, leading to an unbalanced representation of the claimant’s actual abilities.

 

A Comprehensive Approach
Extensive research has shown that in a forensic setting, like an insurance claim, a comprehensive and fixed set of tests, all of which were standardized on the same group of people, is the most valid approach. This approach is called a fixed comprehensive standardized test battery. The most commonly used test following this approach is called the Halstead-Reitan Neuropsychological Test Battery.

 

The individual tests comprising the battery are selected for their accuracy in measuring the functional domain they address and the extent to which each test contributed to the accuracy of the entire battery in diagnosing individual patients. The neuropsychologist employing a fixed battery does not need to employ guesswork to select tests. The same tests are given to every patient regardless of the presenting complaints or the reason for referral. This ensures that all areas are adequately assessed.

 

One major disadvantage of this approach is time. Since every claimant gets every item, healthy claimants waste hours of expensive time completing tests that assess functional domains in which they obviously have no impairments. The lengthy administration time makes it impractical to re-assess the claimant for improvement and parallel forms of the tests, which are necessary to eliminate practice effects, are not available.

 

There is also one seldom discussed “secret” about neuropsychological tests that is as much of a problem for this comprehensive approach as it is for the flexible approach. There is little or no evidence linking performance on most neuropsychological tests to real world functional behaviors (e.g., typing, driving, shopping, taking medications as prescribed, etc.). This is known as a lack of ecological validity.

 

A new solution
The Neuropsychological Assessment Battery (NAB) published by PAR (parinc.com) is a new fixed comprehensive standardized neuropsychological test battery that addresses the problems noted above. The NAB was created and developed over a 7-year period and was funded, in part, through grants from the National Institute of Mental Health. Decisions pertaining to the content and format of the NAB were guided by the results of the publisher’s national survey of neuropsychological assessment practices and needs, as well as by the feedback and guidance of members of the NAB Advisory Council (a group of experts recognized nationally in the field of clinical neuropsychology) and numerous other consultants and contributors.

 

The NAB can be administered to adults ages 18-97 years old who have known or suspected disorders of the central nervous system. The individual tests are grouped into six modules: Attention, Language, Memory, Spatial, Executive Functions, and Screening, and correspond to the hierarchical model discussed above. Each module includes a Daily Living Test that relates skills in that domain to real-world tasks of everyday living, overcoming the lack of ecological validity common to other approaches.

 

Innovative Features of the NAB
  • Screening for both normal and impaired performance
  • Comprehensive coverage of functional domains
  • Combined strengths of the flexible and fixed battery approaches
  • Avoidance of floor and ceiling effects
  • Reduced administration time
  • Entire battery normed on a single standardization group
  • Provision of an equivalent parallel form
  • Focus on ecological validity

 

The screening module allows the neuropsychologist to provide a comprehensive assessment, and saves time and money by thoroughly assessing only those domains the screening has identified as likely aberrant. This allows administration of the NAB in as little as 4 hours compared to 12 hours for the Halstead-Reitan.

 

The NAB allows for seven different combinations of screening tests, module administration and specific test administration. That allows neuropsychologists accustomed to the flexible approach to benefit from using a comprehensive standardized battery while still exercising their professional preference for a flexible assessment approach in which they choose specific tests. Two equivalent forms facilitate reevaluation without any concerns about practice effects.

 

Extensive validation evidence for the NAB exists from clinical studies of patients with dementia, aphasia, traumatic brain injury, attention-deficit/hyperactivity disorder, multiple sclerosis and HIV/AIDS. Other validity studies focused on function independence in an inpatient rehabilitation hospital and a group of simulated malingerers. Studies of these patients has resulted in a large range of test item difficulty so that the results for an individual claimant are not limited by a lack of easy enough items for impaired claimants (aka “floor effect”) or a lack of difficult items for intact claimants (aka “ceiling effect).

 

The NAB was released in 2001 and revised in 2003, but it still is not commonly seen in independent neuropsychological examinations done for insurance claims. That is a shame. Claims adjusters are well advised to request it by name because it offers the most modern and valid approach to neuropsychological assessment in a forensic context.
 


Steven Carter, PsyD, LP, is CEO of Clarius Health, which provides medical evidence analysis, independent examinations and testimony nationwide. He has been a CLM Fellow since 2011 and can be reached at steven@clariushealth.com or (218) 305-4588, www.clariushealth.com.

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