MEASUREMENT OF RELIABILITY AND VALIDITY O F CLINICAL INSTRUMENTS

In biomedical measurement, comparisons between two instruments or betw een a new instrument and the gold standard is commonly needed to evalu ate the reliability and validity of the instruments. Such studies are frequently analyzed using statistics that are inappropriate for studyi ng concordance. This article reviews the appropriate statistical techn iques and provides a current methodological guide for the evaluation o f reliability and validity of instruments used in the measurement of b iomedical variables. The techniques are illustrated using real data fr om a pilot study comparing four instruments for measuring cholesterol.