All responses by L.N. Matheson, PhD
I have published a lot of research on this question. The basic strategy is to use an evaluation that is sensitive to consistency across trials and between different tests. In my clinic, I use a combination of the Spinal Function Sort and EPIC Lift Capacity for people with back injuries and the Hand Function Sort and Jamar Hand Dynamometer and B&L Pinch Gauge or LIDO WorkSET for people with upper extremity injuries. I also look at consistency within each set of tests with tests that are repeatable, like the Jamar, and for force curve variability on the FOCUS hand or pinch strength tests from BTE Technologies.
The EPIC Lift Capacity is extremely sensitive to “less than full effort” when used by a trained and certified person. I frequently get comments that evelautors are amazed at its ability to detect less than full effort. A useful reference is: Matheson, L., Bohr, P., & Hart, D. (1998) [abstract available]. Use of maximum voluntary effort grip strength testing to identify symptom magnification syndrome in persons with low back pain. Journal of Back and Musculoskeletal Rehabilitation, 10, 125–135.
Start with the definition for malingering found in the American Psychiatric Association’s Diagnostic and Statistical Manual for Mental Disorders (DSM–IV). I use a combination of an intake interview and performance testing such as I described above. Both are necessary. If the evaluee does not meet the DSM–IV criteria as established in the intake interview, inconsistent performance test results are often due to problems with depression, fear of re-injury, or mistrust of the evaluator.
I have been addressing the problem of malingering for more than three decades and have not found a single test that provides adequate sensitivity and specificity for its identification.
I would like to recommend that you take a look at the issue of symptom magnification syndrome as an alternative to malingering. Malingering is a differential diagnosis within symptom magnification syndrome, and sometimes useful but often not. The problem is that people have differential responses to disability and pain that need to be sorted out. It usually is not simply whether or not the person is a malingerer.
The judge trying the case qualifies you, based on your education, training, and experience. You must have expertise based on these three factors that is greater than available to the general public or to another professional who is not trained in the area under question.
The attorneys involved in the case will attempt to qualify or disqualify you before the case gets to court by asking to look at your curriculum vitae. They will pay special attention to the specific training you have had in the area in question and the scientific papers and references you can identify as authoritative. For example, just because you are an occupational therapist, physical therapist, or physician, does not qualify you to offer testimony on FCE; you must also have expertise in FCE. This comes in the form of training, seminars, workshops and readings from established experts.
The highest value is placed on peer-reviewed scientific work, found in your education, training, and experience. If your background involves non-scientific work, even if it came in a professional training workshop, it will not be acceptable in court. Thus, your testimony will not be acceptable, nor will your test results, report or written opinion.
The reliability score is only one component of interpreting the Spinal Function Sort in terms of less than full effort. An interpretation of less than full effort performance is based on everything that you see before you. First, the internal consistency check, using the reliability score. Next, the pattern of responses and whether or not it makes sense. Next, the total score and how it compares to the Physical Demand Characteristics chart. Next, the percentile ranking and how it compares to the person’s performance in general, relative to gender and disability group. Finally, I pick a few low items and inquire of the client. If the client is able to provide me with a plausible explanation of the low score for each of the items, I am more likely to accept that his or her responses were reliable. Given this, I provide the following information about the utility of the Spinal Function Sort to identify less than full effort.
The Spinal Function Sort has an internal consistency check. (Explain this process). In addition, we also consider the pattern of responses and whether or not it makes sense, using our professional judgment. In addition, the total score is used to compared to the Physical Demand Characteristics Chart (show chart) which can be tied both to the evaluee’s performance in the functional capacity evaluation and to the history that the person provided me in terms of reported functional tolerances before we began the functional capacity evaluation. In addition, the score can be used to give us a percentile ranking, comparing the person to other persons with disability as well as to healthy persons of the same gender. Finally, I selected a few items that the evaluee scored himself low on and ask the evaluee to explain why the score was low. The evaluee’s explanation provided additional information that I was able to used to determine whether or not this person gave full effort.
If you want to reference the 1996 Cal-FCP paper, that can also be helpful. Also, be sure to review the Spinal Function Sort examiner’s manual that describes the development of the Spinal Function Sort, which can provide you additional useful information. For example, the selection of the items for inclusion in the Spinal Function Sort was based on items that clients at a rehabilitation center reported that they were able to provide an estimate of ability; items that came up “don’t know” were excluded. Therefore, if another client years later in a rehabilitation center gives us numerous “don’t know” responses, we can begin to understand that this recent client is someone who is different from earlier clients. We begin to entertain the hypothesis that the recent client’s responses are aberrant, and perhaps influenced by other factors.
One of the most useful comparisons to determine full effort is between the Spinal Function Sort score and performance in the functional capacity evaluation. Be aware that the Spinal Function Sort floor (the lowest possible score) is intentionally set very low to be sensitive to less than full effort. Also keep in mind that achieving the Sedentary PDC level in the functional capacity evaluation is extremely easy. For example, if the person is able to complete EPIC Lift Capacity subtest 1 through subtest 3 and achieve 10 pounds as a maximum acceptable weight for test 3, a rating of Sedentary is appropriate. If the person’s score on the Spinal Function Sort is substantially below 100, this tells us that the perception of the person’s ability is much less than the person’s tested ability. Upon inquiry, this person should be able to provide us with a plausible explanation of the discrepancy. Often, the explanation will include information that helps us to understand that the ! person is over limiting, perhaps to avoid painful benign symptoms. This is excellent information that can be used to constructively confront the client so that this self-limiting behavior does not continue.
The lifting and lowering normal values are closely tied to a particular test. The structure of the test is intimately tied to the subject’s performance. It’s analogous to IQ in that only 1 test is the standard test of IQ, though there are crosswalks from other similar tests, with the inferred IQ always couched within a confidence interval of +/- 8 IQ points or more.
Also, there are several studies in the ergonomics literature that have looked at predictors of lift capacity and each has found that there are many contributing factors. You might take a look at “Contribution of Aerobic Fitness and Back Strength to Lift Capacity”.
The only large-scale data collection effort that I know of is our own. We have two published studies cited and continue to collect data and have approx 3200 healthy normal subjects. We are working on a paper to present additional gender and age-based norms on this dataset; it should be out by year’s end.