The High Price of Diagnostic Error

I have made it my mission to help increase awareness of “patient safety” in laboratory medicine, and in particular demonstrate the link between laboratory-associated and diagnostic errors. The latter are the leading cause of paid malpractice claims in the USA – twice as many claims than any other type of medical error (1)! Recent data show, among malpractice claims, diagnostic errors are the most common source, most costly and most dangerous of medical mistakes for both inpatients and outpatients (1,2). Diagnostic errors, therefore, are common, produce avoidable disability and death, and yet, worryingly, they remain a relatively understudied and unmeasured area of patient safety (3).

Why this limited recognition? In part it’s because they are difficult to define and measure. The best definition for diagnostic errors is, I believe, “errors in which diagnosis was unintentionally delayed (while sufficient information was available earlier), wrong (another diagnosis made before the correct one), or missed (no diagnosis made) as judged from the eventual appreciation of more definitive information (for example, autopsy studies)” (4). The etiologies of such errors are numerous and the sources categorized as “cognitive”, “system-related” or “no-fault” factors (4) – and laboratory errors play a fundamental role in this context.

The evidence for the importance and direct link between diagnostic errors and errors in laboratory medicine derives from a series of studies that have a clinical starting point. In particular, studies performed on the pre-preanalytical phase confirm that failure to request appropriate diagnostic tests (laboratory tests included) makes up 55 percent of missed and delayed diagnoses in the ambulatory setting (5) and 58 percent of errors in emergency departments (6). In the final stages of the test loop, incorrect interpretation of diagnostic or laboratory tests cause a large percentage of errors in the ambulatory setting and in emergency departments (7). For example, failure to inform patients of clinically significant abnormal test results or to record the delivery of relevant information is relatively common, and has been found to occur in one out of every 14 tests. The overall rate of failure to inform the patient or to record communication of information is 7.1 percent, and in different practices, it ranges from zero to 26 percent (8).

And the evidence continues to mount… The literature shows failure to follow-up test results markedly compromises patient safety, yet the rate of abnormal laboratory results without follow-up (for INR [international normalized ration] and PSA [prostate specific antigen]) ranges from 6.8 to 62 percent! (7). Further evidence of erroneous reactions to laboratory information is provided in a study evaluating the prescription of potassium in cases of hyperkalemia (9). And, findings in another study (10) showed that over 2 percent (2.6 percent in 2000, 2.1 percent in 2007) of patients with thyrotropin (TSH) levels exceeding 20 mU/mL were not followed up. Yet another study revealed that of 1,095 discharged patients, almost half had pending laboratory and radiology test results, 9 percent of which were potentially actionable (11).

Overall, data reported demonstrate that the initial and final steps of the total testing process, above all test requesting and reaction to laboratory results, are not only more error-prone than all the other steps, but are also the most important causes of potential adverse outcomes for patients. The data also confirm that a relevant number of failures occur in the interface between clinicians’ clinics and laboratories, which emphasizes the need for closer cooperation and interaction at the clinical-laboratory interface (12).

The current nature of laboratory testing-associated errors – in particular the link between appropriateness in test ordering and result interpretation/utilization – and their potential in addressing diagnostic errors, should herald a change in the old paradigm which focused only on errors detected within the laboratory walls (13–15). Translating the concept of “patient-centered care” from theory to practice is essential for investigating, and improving, not only all procedures and processes performed under the direct control of the clinical laboratory, but also the initial and final steps of the testing cycle that are usually managed by other healthcare operators. In my experience, a fundamental tool for allowing the identification and minimization of errors in the total testing process is the development of a harmonized model of quality indicators, such as that proposed by a Working Group of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) (15,16).

Mario Plebani is a full professor of Clinical Biochemistry and Clinical Molecular Biology at the School of Medicine, University of Padova, Italy. He is also chief of the Department of Laboratory Medicine at the University-Hospital of Padova, chief of the Center of Biomedical Research (Veneto Region). As well as his academic, medical and management duties in Padova, he is an honorary professor at the University of Buenos Aires (Argentina). His main areas of research are quality in laboratory medicine, diagnostic and laboratory errors, biomarkers in cancer and cardiovascular diseases, and in vitro allergy diagnostics.