Variation in diagnoses: influence of specialists' training on selecting and ranking relevant information in geriatric case vignettes.

Variation in aspects of medical practice such as diagnosis, has been studied at different levels of aggregation. At the inter-practitioner aggregation level, attention is increasingly being paid to factors explaining medical variation which are attributed to 'professional uncertainty'. The concept of 'professional uncertainty' refers to variability that is considered to be inherent to the nature and structure of medical knowledge which depend on the epistemological characteristics of medical science. In this study the relationship between specialty training and variation in diagnostic practice was examined at the inter-practitioner aggregation level. Determination of a direct relationship would support the thesis that specialization is a structuring factor in the inherent variability of medical practice. Three groups of medical specialists participated in the study: geriatricians, geriatric-psychiatrists and internists. Four case scenarios were submitted to the specialists. The cases used involved elderly patients presenting with problems in domains common to all the participating specialists. For each case the specialists were requested to select those facts they considered important for reaching diagnoses and to rank these facts in order of perceived salience. Subsequently they were asked to provide (tentative) diagnoses, ranked in order of perceived significance. The occurrence of variability in diagnostic practice due to 'professional uncertainty' and the influence of specialist specific factors and shared knowledge, respectively, are demonstrated. The results clearly show that these three groups of specialists focused on different elements of information, and formulated different diagnoses in the same case, but expressed similar ranking patterns.