The immediate objective of the diagnostic process is to arrive at a correct diagnosis, and the ultimate goal is to institute appropriate treatments. However, because of the uncertainty that pervades the diagnostic process, there is always the risk that the process ends up in diagnostic failure. Indeed, so pervasive and significant is the problem of diagnostic error that John Scarpello, in his article titled Diagnostic error: the Achilles’ heel of patient safety?, described it as the hidden elephant of patient safety. And this is because getting the diagnosis wrong sets off a chain of events that eventually culminates in patient harm.
Pat Croskerry and G Nimmo portrayed the huge scale of medical diagnostic failure in their paper titled Better clinical decision making and reducing diagnostic error. Stressing that diagnostic failure is ‘frequent and under-appreciated‘, they pointed out that its estimated prevalence of 10-15% makes it ‘the second leading cause of adverse events‘. Similarly, Laura Zwaan and colleagues, in their paper titled Patient record review of the incidence, consequences, and causes of diagnostic adverse events, depicted the dangers of diagnostic failure when they noted that it is present in 0.4% of hospital admissions, 96% of which result in predominantly preventable harm.
To further appreciate the grave consequences of diagnostic failure, Tejal Gandhi and colleagues investigated about 300 closed malpractice claims in which the diagnosis was either missed or delayed. Their findings, published in a paper titled Missed and delayed diagnoses in the ambulatory setting: a study of closed malpractice claims, showed that 60% of these cases resulted in patient harm, with two-thirds being serious, and a third resulting in death.
There are various causes of diagnostic failure and these were discussed by Pat Croskerry in the book Advances in Patient Safety: From Research to Implementation (Volume 2: Concepts and Methodology). He classified diagnostic errors into three on account of their causative mechanisms. The first are the systemic diagnostic errors which arise from such system factors as inadequate staff and a slow turnaround time for investigations. These factors impose a trade-off between speed and accuracy, a forced choice that results in diagnostic failure. The second are the no-fault diagnostic errors which arise when diseases manifest silently or in unusual forms, or when diseases mimic more familiar or more common disorders.
The third class, cognitive diagnostic errors, account for the bulk of diagnostic failures, and these are the most amenable to correction. We will therefore explore these in more depth in the next post.