Today I had the opportunity to use AMA 6. It took me between 15-20 minutes to do the impairment assessment using chapter 4. There are three measures. The Brief Psychiatric Rating Scale, the GAF and the PIRS. The BPRS, as you know is used mainly in inpatient facilities for people with serious mental illness to assess the response to treatment. In this case it is used as a one-off measure and many of the 26 items such as suspiciousness, hallucinations, unusual thought content, bizarre behaviour, self-neglect, disorientation, conceptual disorganisation, excitement, distractibility, mannerisms and posturing are not relevant to the type of disorders that we see. One is expected to score each of these 26 items between 1 to 7 and then add up all the numbers. Arbitrarily the summed score is related to an impairment score e.g. 41-45 equals 15%. The GAF as you know divides groups of symptoms into decades and again arbitrarily a percentage score has been attached to each decade, for example 31-40 equals 20%. Above 70 the impairment score is 0%. You then use the descriptors in the PIRS to get numbers for each function and add the two middle numbers. This sum is then used to determine the PIRS impairment score. So a sum of 5 equals 15%, a sum of 6 equals 20%, a sum of 8 equals 40% (this is different to the combining method used in the PIRS in Australia).
You are then expected to get the middle of these three scores. This is the final impairment rating. It is time consuming, without any validity and with no pretence at equity. I was so annoyed I sent an email to one of the Australian contributors to AMA 6 who assured me that because of its time-consuming assessment process it would never be used here more generally, although it is used in the Northern Territory motor accident system where the legislation requires use of the current edition of the AMA Guides.