To the Editor:I refer to the paper by Ryu, Hong, Jung, Hwang, Jung, Jeong, Rah and Suh (2009) (1).The assessment of psychiatric disability is difficult and fraught with methodological problems and the review by Ryu and colleagues tends to perpetuate the use of methods of assessment which have no firm evidence base as well as ignoring some significant problems with the use of the American Medical Association Guides as well as the Psychiatric Impairment Rating Scale (PIRS).To be fair there is little in the way of objective evaluation of assessment scales in the literature. However data were published providing some validation of the use of the PIRS in 2008 (2, 3). This endeavoured to provide some empiric evaluation and a basis for further research.A problem arising in the review is the omission of a comment that the PIRS is not designed to assess disability for work, being specifically mandated for the assessment of non-economic loss. Because of this it cannot be directly compared to the AMA 6th Guidelines in regard to whole person impairment. Also the Brief Psychiatric Rating Scale (BPRS) was specifically designed for the assessment of psychosis (4) and most patients presenting for evaluation in the context of compensation present primarily with anxiety and depressive disorders.Current research is focussed in two areas. The assessment of fitness for work, in which there are three main components, availability to work, the ability to interact with others and performance of work place duties, and the assessment of non work related disability. Early studies in this second domain indicate four major areas of disability to be assessed, one reflecting the effects of stigmatisation, one relating to self care and relationships with family, one relating to cognitive function such as memory and decision making and one related to interactions with the wider community.There are a number of other wider issues concerning the validity of the use of a percentage scale when the data are of an ordinal rather than interval nature which also deserve consideration by the authors.Yours sincerely,Thank you very much for your correspondence to our article.The purposes of our article were to compare recently developed Korean Academy Medical Sciences (KAMS) guidelines for rating impairments and the AMA 6th Guidelines which has been used most widely and to consider the applicability of this guidelines in Korean situation.As you pointed out, PIRS, GAF and BPRS have their limitations in rating the impairment. In the AMA 6th Guidelines, to make up for the weak points in each scale, they used the median scores of the three scales.In Korea, we have not used these scales because of these limitations. However we agree that estimation of the impairment should be objective as the AMA 6th Guidelines recommend. We have no scales or methods to objectify the impairment yet, but the objectifying study is in progress at present. Since the present Korean rating system was developed on basis of impairment not of disability, we never considered fitness for work.I agree with your opinion which mentions lack of firm evidence in our guideline. However AMA also made their first guideline on scoring the impairment in mental and behavioral disorders in the 6th Guidelines, therefore we thought that our effort was not out of date. The percentage of impairments in each disease can be diverse in each country due to national situation and attitude toward the disease. The percentage system in our article is based on the Korean law and it has been widely used in our country. This law was made on a political logic not on medical, and lack of medical evidence is the limitation. The KAMS is carrying out a study on validating it. When this validating study is finished, our KAMS guidelines will have more medical evidence.In Korea, there were little studies on psychiatric impairments, and rather subjective and empirical evaluation and rating have been performed. We look forward to beginning more objective and fair rating the psychiatric impairments and increasing the systemic study on these issues in Korea through our new guidelines. Thank you very much for your pointing out limitations of our article.