Assessing physicians' accuracy in diagnosing paediatric patients with acute abdominal pain: measuring accuracy for multiple diseases

In evaluating the accuracy of diagnostic tests there are many situations wh ere the true disease status can be one of multiple disorders. For example, when paediatric patients suffer acute abdominal pain, the underlying diagno sis could be appendicitis, intestinal obstruction, gastroenteritis, urinary tract infection, etc. In this paper we describe a format for collecting da ta for the case of multiple truth states. This new format allows one to mak e pairwise comparisons of the diagnostic accuracy between all of the differ ent truth states. We propose a summary measure of accuracy which is a weigh ted average of the pairwise estimates of accuracy. Estimators are derived f or the variance and covariance of the estimated summary accuracy. The small sample properties of the estimators are evaluated in a Monte Carlo simulat ion study. The now data collection format and summary measure were used in a paediatric acute abdominal pain study; data from this study are used to i llustrate the methods. Copyright (C) 2001 John Wiley & Sons, Ltd.