The role of rating scales in psychiatry.

The first application of rating scales in psychiatry goes back to soon after the First World War, but the real development did not occur until after the Second World War. Their use has increased so much that it is scarcely possible to look through any copy of a general psychiatric journal without finding at least one paper which involves the use of a scale of some sort. Such papers are always concerned with research; up till now the only attempt to use rating scales in clinical practice has been related to the efforts made to store case records on computers. The term 'rating scale' was originally used to define a series of items which quantified or placed in rank order, the manifestations of a single variable, e.g. aggressiveness. Another form of rating scale was applied to individuals to quantify the extent to which they possessed a given attribute, e.g. persons could be rated on their aggressiveness. For most purposes, especially clinical, the term is often used to describe a set of scales which have some intrinsic relationship to each other. The individual scales are then referred to as items of the total scale. There are many kinds of scales in current use and they can be classified in different ways. The most obvious is in terms of the user: self-rating scales and those used by an observer, who can be skilled, e.g. psychiatrist or psychologist, or semi-skilled such as a nursing aid, or unskilled, e.g. the relative of a patient. The data of the first type can be obtained from structured, semi-structured or free interviews. Classification can be according to the form of the items: graded items record degrees of severity or relevance; in checklists the items are scored as present or absent; and there are forced-choice items in which the rater has to choose which of two alternatives is most applicable. Scales can also be considered in relation to their content, e.g. symptoms, behaviour in the ward, social adjustment, family relations, functional capacity in an occupational therapy or an industrial therapy setting. Finally, and most important, scales can be classified according to their function. There are four of these: (1) intensity scales which measure severity of illness and also response to treatment; (2) prognostic scales, including prediction of response to treatment; (3) scales for selection of treatment by means of differential indicators; and, finally, (4) scales for diagnosis and classification. A number of misconceptions about rating scales must first be considered. A rating scale is only a particular device for recording information about a patient. The data provided by it are therefore no better than their basis. Inadequate, misleading or incorrect information is not improved by recording it on a rating scale. For clinical purposes, the best way of describing a patient is by a free and full psychiatric case history. When this is reduced to a rating scale, much information is lost. For some purposes the loss may be serious, but in appropriate circumstances it may be of no account. In a sense, rating a patient is fitting him into a Procrustean bed; anything which does not conform to the requirement of the scale has to be ignored, i.e. deleted. For example, the rating of a schizophrenic patient on a scale for depression would certainly produce a set of scores and it is conceivable that they might have some sort of meaning, but they do not give an adequate description of the patient's condition. The reverse also occurs. The presence of a large number of irrelevant items in a scale encourages raters to attempt to fill in at least some. Although the information provided by a rating scale is limited, it is valuable because it is uniform for all patients and all occasions, and it is standard in its significance because the items, their grades and manner of use have been previously defined. Rating scales therefore permit comparison between different patients and between different occasions for the same patients. They do this with adequate reliability and validity, which is more than can be said for 'free' case histories and diagnostic labels.