The Institute of Medicine report To Err Is Human: Building a Safer Health System (1) and other reports (2-5) have increased concern over the negative impact of medical errors on public health and patient care. Although the Institute of Medicine report presented few data on errors in laboratory medicine, it had wide-reaching implications for all disciplines. Because data from clinical laboratories are directly involved in the vast majority of all medical diagnoses and treatments (6), there is an increasing awareness of the importance of errors in laboratory practice and their possible negative impact on patient outcomes. Many strategies are used to reduce laboratory errors, including internal quality control procedures, external quality assessment programs, certification of education programs, licensing of laboratory professionals, accreditation of clinical laboratories, and the regulation of laboratory services. In the past, laboratory professionals focused their attention on analytical errors and mistakes resulting in adverse events but overlooked errors in the preanalytical and postanalytical steps. In 1996, we demonstrated that pre- and postanalytical processes in our laboratory were more vulnerable to errors than the analytical steps (7). The results of our study and others (7-9) have led to wide agreement that the total testing process is the best framework for evaluating and reducing error rates in laboratory medicine and wide acceptance of the proposed definition for laboratory error as a defect occurring at any part of the laboratory cycle, from ordering tests to reporting, interpreting, and reacting to results (8, 9), a definition that has been incorporated in the ISO Technical Report 22367 (10). The aim of the present study was to compare our 1996 data on errors with data collected 10 years later in the same clinical context, using the same study design for both investigations.
