Determining Overall Mental and Behavioural Impairment

1. Determining Overall Mental and Behavioural Impairment A Clinical and Scientific Perspective

2. There are two questions being hotly debated • Can we combine bodily with mental and behavioural impairments? • How do we determine an overall impairment?

3. My focus is on the second question: How do we determine an overall impairment?

4. Determining what catastrophic impairment means is a legal issue this issue is not mentioned anywhere in the AMA Guides.

5. Determining whether someone has an overall marked impairment according the AMA Guides is a clinical and scientific issue.

6. Alternative Perspective I am not a lawyer, so I am not bringing you a legal perspective.

7. Psychologists are trained as clinicians and scientists. These are the alternative perspectives I am bringing to today’s discussion.

8. So, what is an overall?

9. To understand what constitutes an overall impairment rating, we must look at two sources… • The AMA Guides • Scientific Measurement Principles

10. What is the AMA Guides?

11. The first edition of the AMA Guides to the Evaluation of Permanent Impairment was published 40 years ago, in 1971, as a set of separate guides to evaluate different kinds of impairment, all brought under one cover.

12. The “guides” were originally published as separate papers between 1958 and 1970 in the Journal of the American Medical Association (JAMA).

13. There are 6 editions of the Guides. The SABS instruct us to use the 4th edition, 1993.

14. The chapter in the 4th edition relevant to our discussion is chapter 14: Mental and Behavioral Disorders

15. Chapter 14 lays out a basic framework for assessing and rating mental and behavioural impairment.

16. It describes 4 functional classes: • Activities of Daily Living • Social Functioning • Concentration, Persistence and Pace • Deterioration or Decompensation in Work or Work-like Settings

17. Each class looks at human functioning through a different lens.

18. While they are described as different classes, they overlap significantly.

19. A basic example of overlap: Shopping can be considered in the ratings for each class.

20. There are 5 impairment levels used to rate impairments in chapter 14: • Nil • Mild • Moderate • Marked • Extreme

21. The ratings are defined qualitatively, and some examples are given to help assessors to apply them correctly.

22. Assessors do a psychological assessment in order to gather enough clinical information to rate impairment levels in each of the four classes.

23. This brings us back to the question: What is an overall?

24. First – what is it not?

25. An overall is not an average An average tells you nothing about what is happening overall.

26. If we looked at average impairment, we would underestimate a person’s overall impairments, as well as treatment and care needs.

27. To understand the idea of an overall impairment better, we have to look at: • what exactly is being measured • what kind of measure or scale is being used

28. Reminder: Chapter 14 asks assessors to rate overlapping categories that each get at human functioning from a unique perspective.

29. We’ve already reviewed what is being measured in the chapter that covers mental and behavioural impairments.

30. The question remaining is… what kind of measure does the Guides instruct us to use?

31. This leads us to the most exciting topic possible…

32. STATISTICS! (woo hoo!)

33. What is about to follow are basic statistical principles, not my opinion…

34. What we can do with various measurement or scale ratings depends on the kind of scale we use.

35.  Stanley Smith Stevens, a psychologist from Harvard, wrote about this in a classic 1946 article, “On the theory of scales of measurement”

36. There are only four different types of measurement scales that are used in science: • Nominal • Ordinal • Interval • Ratio

37. The basic idea is that the type of scale we use will determine what we can do with it statistically when offering opinions that are scientifically sound.

38. The measurement scale used to rate the classes in chapter 14 is an ordinal scale.

39. What is an ordinal scale?

40. Just like it sounds, an ordinal scale offers measuresments that are in a simple order.

41. They can be numbered in rank order, such as 1st, 2nd, 3rd, 4th

42. Or the scale rankings can have names assigned to them, such as nil, mild, moderate, marked, and extreme.

43. Sound familiar?

44. The important point is that this scale can only describe order

45. It is not possible for ordinal rankings to tell us anything about relative size or the difference between rankings.

46. Because of this, when we use an ordinal scale, a basic statistical principle that we are stuck with is that there is no way to average things measured on this scale.

47. So that means that when people try to average the class ratings, they are not using a scientifically valid approach.

48. An average of the ratings given for the four classes in chapter 14 is not meaningful from a scientific or clinical perspective.

49. Making matters worse, the classes being measured are overlapping categories - An average of an overlapping ordinal is even more meaningless.

50. “It’s a moo point. It’s like a cow’s opinion. It doesn’t matter. It’s Moo.” --Joey from the television show, ‘Friends’