Observer variation in clinical practice. A review

: Observer variation denotes the discrepancy between two consecutive observations of the same indicant. Principles and results of observer variation studies are outlined. Observer variation seems to be present wherever it is searched for, in history taking as well as in physical examination. It has been found unanimously to be smaller for intra- than for inter- observer variation while it is still controversial whether clinical experience lessens observer variation. Even fundamental clinical observations and particularly evaluations of borderline cases between normal and abnormal exhibit observer variation. The possibilities of reducing observer variation, and the importance of observer variation to clinicians and patients, and also the influence on research and society are referred to briefly. The future role of observer variation studies is discussed. Observer variation often is evaluated by the Kappa statistics whose statistical advantages and clinical disadvantages are outlined.