When is rational to order a diagnostic test, or prescribe treatment: the threshold model as an explanation of practice variation
Physicians are often forced to act (e.g. order a diagnostic test or prescribe treatment) in face of diagnostic uncertainty. Theories of decision-making indicate that physicians should act when the benefit of such an action outweighs its harms (for a given probability of disease). According to the threshold model when faced with uncertainty about whether to treat, order a test, or simply observe the patient, there may exist some probability of disease at which a physician is indifferent between administering versus not administering treatment and ordering versus not ordering a diagnostic test . These are known as the treatment threshold, the test-treatment threshold and testing threshold, respectively.
If physicians estimate treatment benefits, treatment harms, and test performance similarly, and integrate those into a threshold which they heed, this would result in more uniform medical practice. However, a vast body of empirical research has demonstrated significant variation in medical practice: seemingly similar patients are treated differently by diferent physicians.
Why is this so?. The authors explain in the
article the differences between normative thresholds and descriptive ones and what to do about it: change the perspective - ‘target decision making, not geography"-. (?). A must read.
We demonstrate here that the threshold concept ultimately relates to the question of rational decision-making. Surprisingly, however, little empirical work has been published on the threshold models, or using the threshold concept as a theoretical platform to investigate clinical decision-making. This calls for the renewed interest in comparing ‘derived [or descriptive] thresholds with prescriptive thresholds obtained by decision analysis’, the call which was issued almost 30 years ago but left unheeded probably because of the lack of theoretical developments. However, the last 30–40 years have seen remarkable theoretical developments in the fields of cognitive sciences and decision-making such as dual-processing theories that have emerged as the important contenders for redefinition of rational choice. Understanding which theory underpins physicians’ and patients’ decision-making must be a key policy and research priority.
