A scale for assessing the severity of diseases and adverse drug reactions. Application to drug benefit and risk.

Physicians were interviewed to assess their willingness to risk adverse drug reactions among patients. These untoward reactions were ranked according to severity and weighted against the primary illness being treated. A specially designed questionnaire in the form of a matrix was used. Severity was divided into seven classes denoted by progressively increasing numerical scores, W1 to W7, whose values could be calculated from analysis of the completed questionnaires. The questionnaires presented several cases, in each of which an illness of specified severity was to be treated with a drug whose untoward reactions differ in severity from that of the primary illness. Each case involved a different permutation of the severities. Analysis of the completed questionnaires yielded the mean values of the scores which were found to range from W1 = 1.00 (the mildest case) to W7 = 817 (the most serious case). It is our opinion that this type of scale is preferable to nonnumerical descriptions of severity such as "mild" or "serious," since, when combined with data on frequency of occurrence, a numerical scale permits a determination of expectation of both benefit and risk.