Missed and Delayed Diagnoses in the Ambulatory Setting: A Study of Closed Malpractice Claims

Context Efforts to reduce medical errors and improve patient safety have not generally addressed errors in diagnosis. As with treatment, diagnosis involves complex, fragmented processes within health care systems that are vulnerable to failures and breakdowns. Contributions The authors reviewed malpractice claims alleging injury from a missed or delayed diagnosis. In 181 cases in which there was a high likelihood that error led to the missed diagnosis, the authors analyzed where the diagnostic process broke down and why. The most common missed diagnosis was cancer, and the most common breakdowns were failure to order appropriate tests and inadequate follow-up of test results. A median of 3 process breakdowns occurred per error, and 2 or more clinicians were involved in 43% of cases. Cautions The study relied on malpractice claims, which are not representative of all diagnostic errors that occur. There was only moderate agreement among the authors in their subjective judgments about errors and their causes. Implications Like other medical errors, diagnostic errors are multifactorial. They arise from multiple process breakdowns, usually involving multiple providers. The results highlight the challenge of finding effective ways to reduce diagnostic errors as a component of improving health care quality. The Editors Missed and delayed diagnoses in the ambulatory setting are an important patient safety problem. The current diagnostic process in health care is complex, chaotic, and vulnerable to failures and breakdowns. For example, one third of women with abnormal results on mammography or Papanicolaou smears do not receive follow-up care that is consistent with well-established guidelines (1, 2), and primary care providers often report delays in reviewing test results (3). Recognition of systemic problems in this area has prompted urgent calls for improvements (4). However, this type of error remains largely unstudied (4). At least part of the reason is technical: Because omissions characterize missed diagnoses, they are difficult to identify; there is no standard reporting mechanism; and when they are identified, documentation in medical records is usually insufficiently detailed to support detailed causal analyses. The result is a relatively thin evidence base from which to launch efforts to combat diagnostic errors. Moreover, conceptions of the problem tend to remain rooted in the notion of physicians failing to be vigilant or up-to-date. This is a less nuanced view of error causation than careful analysis of other major patient safety problems, such as medication errors (5, 6), has revealed. Several considerations highlight malpractice claims as a potentially rich source of information about missed and delayed diagnoses. First, misdiagnosis is a common allegation. Over the past decade, lawsuits alleging negligent misdiagnoses have become the most prevalent type of claim in the United States (7, 8). Second, diagnostic breakdowns that lead to claims tend to be associated with especially severe outcomes. Third, relatively thorough documentation on what happened is available in malpractice insurers' claim files. In addition to the medical record, these files include depositions, expert opinions, and sometimes the results of internal investigations. Previous attempts to use data from malpractice claims to study patient safety have had various methodologic constraints, including small sample size (9, 10), a focus on single insurers (11) or verdicts (9, 10) (which constitute <10% of claims), limited information on the claims (811), reliance on internal case review by insurers rather than by independent experts (8, 11), and a general absence of robust frameworks for classifying types and causes of failures. To address these issues, we analyzed data from closed malpractice claims at 4 liability insurance companies. Our goals were to develop a framework for investigating missed and delayed diagnoses, advance understanding of their causes, and identify opportunities for prevention. Methods Study Sites Four malpractice insurance companies based in 3 regions (northeastern, southwestern, and western United States) participated in the study. Collectively, the participating companies insured approximately 21000 physicians, 46 acute care hospitals (20 academic and 26 nonacademic), and 390 outpatient facilities, including a wide variety of primary care and outpatient specialty practices. The ethics review boards at the investigators' institutions and at each review site approved the study. Claims Sample Data were extracted from random samples of closed claim files from each insurer. A claim is classified as closed when it has been dropped, dismissed, paid by settlement, or resolved by verdict. The claim file is the repository of information accumulated by the insurer during the life of a claim. It captures a wide variety of data, including the statement of claim, depositions, interrogatories, and other litigation documents; reports of internal investigations, such as risk management evaluations and sometimes root-cause analyses; expert opinions from both sides; medical reports detailing the plaintiff's preevent and postevent condition; and, while the claim is open, medical records pertaining to the episode of care at issue. We reacquired the relevant medical records for sampled claims. Following previous studies, we defined a claim as a written demand for compensation for medical injury (12, 13). Claims involving missed or delayed diagnoses were defined as those alleging an error in diagnosis or testing that caused a delay in appropriate treatment or a failure to act or follow up on results of diagnostic tests. We excluded allegations related to pregnancy and those pertaining to care rendered solely in the inpatient setting. We reviewed 429 diagnostic claims alleging injury due to missed or delayed diagnoses. Insurers contributed to the study sample in proportion to their annual claims volume (Appendix). The claims were divided into 2 main categories based on the primary setting of the outpatient care involved in the allegation: the emergency department (122 claims) and all other locations (for example, physician's office, ambulatory surgery, pathology laboratory, or radiology suites) (307 claims). The latter group, which we call ambulatory claims, is the focus of this analysis. Study Instruments and Claim File Review Physicians who were board-certified attendings, fellows, or third-year residents in internal medicine reviewed sampled claim files at the insurers' offices or insured facilities. Physician-investigators trained the reviewers in the content of claim files, use of the study instruments, and confidentiality procedures in 1-day sessions at each site. The reviewers also used a detailed manual. Reviews took on average 1.4 hours per file. To test review reliability, a second reviewer reviewed a random selection of 10% (42 of 429) of the files. Thirty-three of the 307 ambulatory claims that are the focus of this analysis were included in the random blinded re-review. A sequence of 4 instruments guided the review. For all claims, insurance staff recorded administrative details of the case (Appendix Figure 1), and clinical reviewers recorded details of the adverse outcome the patient experienced, if any (Appendix Figure 2). Reviewers scored adverse outcomes on a 9-point severity scale ranging from emotional injury only to death. This scale was developed by the National Association of Insurance Commissioners (14) and has been used in previous research (15). If the patient had multiple adverse outcomes, reviewers scored the most severe outcome. To simplify presentation of our results, we grouped scores on this scale into 5 categories (emotional, minor, significant, major, and death). Appendix Figure 1. Administrative screening data form Appendix Figure 2. Outcome assessment data form Next, reviewers considered the potential role of a series of contributing factors (Appendix Figure 3) in causing the adverse outcome. The factors covered cognitive-, system-, and patient-related causes that were related to the episode of care as a whole, not to particular steps in the diagnostic process. The factors were selected on the basis of a review of the patient safety literature performed in 2001 by 5 of the authors in consultation with physician-collaborators from surgery and obstetrics and gynecology. Appendix Figure 3. Human factors analysis data form Reviewers then judged, in light of available information and their decisions about contributing factors, whether the adverse outcome was due to diagnostic error. We used the Institute of Medicine's definition of error, namely, the failure of a planned action to be completed as intended (i.e. error of execution) or the use of a wrong plan to achieve an aim (i.e. error of planning) (16). Reviewers recorded their judgment on a 6-point confidence scale ranging from 1. Little or no evidence that adverse outcome resulted from error/errors to 6. Virtually certain evidence that adverse outcome resulted from error/errors. Claims that scored 4 (More likely than not that adverse outcome resulted from error/errors; more than 50-50 but a close call) or higher were classified as having an error. The confidence scale and cutoff point were adapted from instruments used in previous studies of medical injury (15, 17). Reviewers were not blinded to the litigation outcomes but were instructed to ignore them and rely on their own clinical judgment in making decisions about errors. Training sessions stressed that the study definition of error is not synonymous with the legal definition of negligence and that a mix of factors extrinsic to merit influence whether claims are paid during litigation. Finally, for the subset of claims judged to involve errors, reviewers completed an additional form (Appendix Figure 4) that collected additional clinical information about the missed diagnosis. Specifically, reviewers