Error in Radiology

Introduction

Errors are innate in every field of medicine and persist despite the best efforts of medical professionals to be (or become) flawless. In fact, the prevalence of errors by radiologists (i.e., the radiology error rate) has been remarkably constant in repeated studies dating to the 1930s. For radiologists, there are multiple contributing factors for this, including knowledge gaps and perceptual errors; flaws inherent in emerging technologies for image acquisition and reliance on the input of other professionals, especially technologists for image acquisition; and referring clinicians, who are relied upon for requesting the most suitable study and providing appropriate historical guidance. The underlying cause(s) of the most common radiologist error—simply failing to perceive a finding that sometime later seems obvious in retrospect—remains unknown. In the face of this harsh reality, it is crucial to create systems to attempt to reduce and prevent error but also to rapidly detect errors when they inevitably occur so that the appropriate remediation and prevention of harm can be accomplished. In approaching the subject of radiologist error, a classification of errors is needed.

Epidemiology of Error

Leo Henry Garland was a radiologist in the mid-20th century. He was the pioneer in studying radiologic error and published an important article on diagnostic error in the American Journal of Roentgenology in 1939. Garland discovered a 30% miss rate when experienced radiologists interpreted positive chest radiographs and found that 2% of negative chest radiographs were overinterpreted. He also found that 20% of radiologists disagreed with themselves on a second reading! His work was not warmly embraced by his colleagues at the time, who were at best hesitant to acknowledge the significance of his results. Since Garland’s time, more recent research on radiologist’s error rates have repeatedly yielded results consistent with Dr. Garland’s initial reporting of error frequency, without any appreciable improvement despite advances in radiologic technology and clinical knowledge. This suggests that the problem is a very basic one, not readily amenable to technological or educational intervention.

In multiple peer-reviewed publications (see Siegle et al.) the most realistic estimates for radiologist error rates are obtained when radiologist’s performance is measured using case samples typical of actual practice, where the mix of studies interpreted includes a blend of normal and abnormal cases with a representative disease prevalence. Studies of this type have generally revealed an error rate of 3.5% to 4%. If the case mix is enriched to include essentially 100% positive studies—a very artificial situation—the error rate rises to approximately 30%. Because most radiologists interpret a mix of studies with a low overall prevalence of positive findings, and because most radiologists interpret well in excess of 100 studies in a typical day, this translates to approximately three or four errors per day per radiologist, on average. Fortunately, only a small fraction of these errors result in patient harm, but it is worrisome that most go undetected; in most cases, radiologists are never made aware of the majority of their errors and receive useful, prompt feedback on an extremely small fraction of their actual errors.

In September of 2015, the Institute of Medicine (IOM) released a new report on the prevalence and range of diagnostic error, entitled Improving Diagnosis in Healthcare . This new IOM monograph, which is part of a series including Crossing the Quality Chasm , which was published in 2001, and To Err Is Human: Building a Safer Health System , published in 2000, once again called attention to the alarming magnitude of the problem, namely, the very large number of diagnostic errors in medicine. The report defined diagnostic error as “the failure to (a) establish an accurate and timely explanation of the patient’s health problem(s) or (b) communicate that explanation to the patient.” Based on that definition, the committee concluded that diagnostic error is so common that most people will experience at least one diagnostic error in their lifetime, sometimes with devastating consequences, and called for urgent change to address this challenge. Postmortem studies spanning many decades estimated that diagnostic errors contributed to approximately 10% of patient deaths, and review of malpractice claims data has shown that diagnostic errors are the most common cause of successful malpractice lawsuits.

Of course, radiologists’ errors account for only a fraction of overall diagnostic error because imaging is only one of many factors that contribute to the diagnostic process. Other contributing factors include faulty information gathering by clinicians, insufficient consideration given to differential possibilities, inadequate performance of a physical examination or misinterpretation of physical exam findings and laboratory tests, lab and pathology errors, failure to act appropriately on the results of monitoring or testing once the results are reported, inadequate communication between caregivers, and so on. But because the specialty of diagnostic radiology exists primarily to reduce the uncertainty in establishing a diagnosis, the report carries significant implications for radiologists.

Types of Errors

Various authors have attempted to provide classification systems for radiologist’s diagnostic errors. The very comprehensive system proposed by Kim and Mansfield (discussed later in this chapter) includes 12 categories of error, although some error types were shown in their study to be much more prevalent than others. In this chapter we limit our discussion to diagnostic errors and do not consider the related issues of treatment, procedural, or medication errors, which are also common causes of patient harm. Often overlooked are errors related to overdiagnosis , in which radiologists contribute to placing a pathologic disease diagnosis on a normal, healthy patient, leading physicians to provide inappropriate (i.e., not indicated) care, such as when a normal appendix is removed because a radiologist misinterprets a normal structure for an inflamed appendix or laparoscopy is done for a presumed ectopic pregnancy due to misinterpretation of an ultrasound artifact. Other types of errors germane to radiologic practice (but not limited to radiology) include communication failures, equipment malfunction, or other system failures.

It is important to realize that, contrary to the prevailing culture within the medical profession, the vast majority of medical errors are not simply due to individuals being reckless, ignorant, incompetent, sloppy, or negligent. To the contrary, research has repeatedly demonstrated that nearly all medical errors are instead due to preventable failures in the systems, processes, and conditions in which caring, competent professionals practice.