The Newcastle Rating Scales

Abstract

Rating scales have three main applications in clinical and scientific work in psychiatry. They may be employed to measure the severity of illness and thereby response to different forms of treatment. Secondly they can be applied to predict the course of illness or the outcome of treatment, and thirdly they can be used to assist differential diagnosis. These three types of scale have to be differentiated from each other. For when the multivariate techniques from which they have been derived are examined it is apparent that their mathematical derivation differs. Severity rating scales are derived from the main general component, extracted by principal component analysis, when this method is applied to investigate the clustering of features within homogenous or closely related disorders. The weights accorded to the different items are derived from their loadings on the main general factor extracted. The second type of scale, that intended to provide an instrument for the prediction of outcome is derived from a stepwise multiple regression analysis of the items that characterise a uniform group of patients whose progress has been systematically recorded over a period. In the case of discriminating scales such as the anxiety/depression scale the scores of the different items are derived from a bipolar factor on which features characteristic of each of the pair of overlapping disorders under investigation, show scores of opposite sign.