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1 Università Vita-Salute San Raffaele, Cattedra di Biochimica Clinica, Via Olgettina 58, 20132 Milan, Italy.
2 Istituto Scientifico H. S. Raffaele, Servizio Integrato di Medicina di Laboratorio, Via Olgettina 60, 20132 Milan, Italy.
3 Servizio di Medicina di Laboratorio, Azienda Ospedaliera di Padova, Via Giustiniani 2, 35100 Padova, Italy.
aAuthor for correspondence. Fax 39-02-2643-2640; e-mail bonini.pierangelo{at}hsr.it.
Abstract
Background: The problem of medical errors has recently received a great deal of attention, which will probably increase. In this minireview, we focus on this issue in the fields of laboratory medicine and blood transfusion.
Methods: We conducted several MEDLINE queries and searched the literature by hand. Searches were limited to the last 8 years to identify results that were not biased by obsolete technology. In addition, data on the frequency and type of preanalytical errors in our institution were collected.
Results: Our search revealed large heterogeneity in study designs and quality on this topic as well as relatively few available data and the lack of a shared definition of "laboratory error" (also referred to as "blunder", "mistake", "problem", or "defect"). Despite these limitations, there was considerable concordance on the distribution of errors throughout the laboratory working process: most occurred in the pre- or postanalytical phases, whereas a minority (1332% according to the studies) occurred in the analytical portion. The reported frequency of errors was related to how they were identified: when a careful process analysis was performed, substantially more errors were discovered than when studies relied on complaints or report of near accidents.
Conclusions: The large heterogeneity of literature on laboratory errors together with the prevalence of evidence that most errors occur in the preanalytical phase suggest the implementation of a more rigorous methodology for error detection and classification and the adoption of proper technologies for error reduction. Clinical audits should be used as a tool to detect errors caused by organizational problems outside the laboratory.
Measuring and improving laboratory-related patient outcomes require methods that relate the total quality of laboratory information to more effective patient management, including diagnosis, treatment of disease, clinical monitoring, and disease prevention. The improvement in analytical quality, documented through proficiency testing, should guarantee that the actual performances of clinical laboratories are suitable for improving a patients health. Furthermore, increased attention to patients needs is demonstrated by efforts to improve the quality of the entire service provided, e.g., reduction of the turnaround time (TAT). However, improvement of laboratory performance does not automatically indicate a reduction in the number of errors, both analytical and organizational. Even certification or accreditation processes focus attention more on the general performance of the laboratory than on events such as errors that, by their very nature, are considered exceptional. Moreover, the lack of a universally accepted definition of error and above all of "allowable error rate", reduces the possibility of evaluating the impact of laboratory error on patient outcomes.
Although there is abundant scientific literature dealing with increased laboratory quality (mainly analytical), the literature on errors in laboratory medicine is scarce. One reason for this, in addition to the insufficient attention paid to the problem, is the practical difficulty in reporting and measuring the number of errors.
In fact, there are several limitations in the study designs of reports dealing with the frequency and types of mistakes in the clinical laboratory.
The first limitation is that most of the studies focus simply on analytical errors, which represent only a percentage of the errors in the total testing process, which includes all pre-, intra-, and postanalytical phases. Other studies are based on methodologies, such as the split-specimen design, that are insensitive to total testing process problems that can occur before specimens are collected and after results are obtained by the analytical process (1)(2).
The second limitation is that it is possible, even probable, that the most frequent preanalytical errors are represented by an inappropriate choice of laboratory tests or panel of tests and that most postanalytical errors derive from inappropriate interpretation and utilization of laboratory results. Although large differences in laboratory test requests and utilization between hospitals, even within the same country, have been described recently (3), a systematic review of laboratory clinical audits has demonstrated that many studies identifying inappropriate laboratory use are based on implicit or explicit criteria not meeting methodologic standards (4).
Regarding the postanalytical phase, only a few studies are available that demonstrate the inappropriate utilization of or response to laboratory results. It has recently been demonstrated that the introduction of new technologic facilities (online connection between laboratory and wards) without proper organization can worsen, rather than improve the communications between laboratories and clinicians (5). The lack of immediate notification and/or clinical utilization of a critical value can have an effect on outcome as negative as a wrong result. As pointed out by Lundberg in an outstanding editorial in JAMA (6), proper interpretation and action must be accomplished before the laboratory test loops are actually completed.
The third limitation is that, apart from a reluctance in reporting their own errors, it is extremely difficult for laboratories to identify all errors because many errors will neither produce detectable abnormal results nor raise questions for the user. Although their observations were not based on actual data, Goldschmidt and Lent (7) estimated that up to 75% of errors produce results still within the reference intervals, that
12.5% produce wrong results that are so absurd that they are not considered clinically, and that the remaining 12.5% of laboratory errors may have an effect on patient health.
The fourth limitation is that new pathophysiologic insights and the development of highly specific and sensitive laboratory tests have changed the relationship between laboratory information and the gold standards. This is the case for myocardial damage in acute coronary syndromes, in which the measurement of cardiac troponins is the method of choice for detecting small myocardial injuries. The same is true for molecular analyses to evaluate disease susceptibility. In this and other clinical situations where it is difficult or impossible to compare laboratory results to gold standards, possible errors should be identified by evaluating the relationship between laboratory information and medical outcomes.
In contrast to the above-described situation, which was derived essentially from the scientific literature, "errors in medicine", including laboratory mistakes and problems at blood banks, are frequently cited by the mass media even if the attention is especially driven by errors in other healthcare sectors (e.g., drugs or surgery). In many of these reports, it is suggested that the reported errors are only the tip of the iceberg and that the consequences on patient outcome are likely to be worse than described. For this reason, we reviewed the scientific literature on errors in laboratory medicine and blood banks.
For laboratory medicine, we searched the MEDLINE database from January 1994 to June 2001 by crossing several headings: "laboratories, diagnostic services"; "chemistry, clinical"; "diagnostic errors"; and "medical errors". All articles with the words "blunders OR problems OR errors OR mistakes AND laboratory" in the title were also selected. Additional hand searching was performed, starting with the references of the selected papers. Finally, only articles reporting information on the total testing process (including the preanalytical, analytical, and postanalytical phases, not just one of them) in which data were obtained by direct collection (not just by questionnaires) were chosen and are compared in Table 1
.
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For blood banks, we searched the MEDLINE database from January 1992 to June 2001 by crossing several headings: blood transfusion/st (standards); blood group, incompatibility/co (complications); blood transfusion/ae (adverse effects); quality of health care; quality control quality assurance; health care/sn (statistics & numerical data); quality assurance, health care/og (organization & administration); quality assurance, health care/st (standards); safety; medication errors; and patient identification systems/st (standards). Starting from these results, we performed additional hand searching and selection. The results are presented in Table 2
and represent only those studies including more than three hospitals or a data collection period longer than 1 year. Only the most recent literature was analyzed because advances in laboratory informatics, automation, and analytical quality would make comparison to older studies nearly impossible (see also Table 3
).
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The most relevant features of the studies involving laboratory errors are summarized in Table 1
: (a) data collection period; (b) number of tests considered; (c) number of patients involved; (d) total number of errors and their relative frequencies; (e) distribution of errors in the preanalytical, analytical, and postanalytical phases; (f) errors caused by patient misidentification; and (g) effect of errors on patient outcome. The findings confirm that there is a very limited number of studies on this topic and that those that exist are very heterogeneous. These studies used different data collection approaches [process analysis (8), audit and questionnaires (9), and collection of complaints (7)], the time span for data collection ranged from 3 months to 10 years, and the laboratory sectors examined were very different. Another obstacle to comparing these studies or reaching general conclusions is that in some reports, the errors are indexed to patients, whereas in others they are indexed to tests performed. Data have been partially re-elaborated to calculate frequencies, to divide them into the phases of the working process, and to harmonize the categories of relevance of the effect on patient outcome. It is evident from the data shown that the collection method has a very strong influence on both the prevalence and the error types. For example, when data collection was based on complaints (7) or on more or less fortuitous finding of blunders (10), the errors reported were mainly attributable to misidentification, and their number was very low: 133 errors in 6 years (7) or 0.05% (10). On the other hand, when a careful review of the whole working process was performed (8), the number of errors increased substantially (189 in 3 months, 0.47% of the test results). In this last report (8), misidentification errors represented only 2.6% of all errors, but their absolute frequency was more than double that reported by Lapworth and Teal (10). The heterogeneity of the literature is even more obvious in Table 3
, where only the frequencies of errors from these and older studies are reported.
One common finding in this review of data on laboratory errors is that even when different study designs, patient numbers, and discovery techniques were used, the distribution of errors across the different phases of the entire testing process was very similar. This comes through despite the large differences in actual error frequencies. In particular, all available studies demonstrated that a large percentage of laboratory errors occur in the pre- and postanalytical phases, with fewer mistakes occurring during the analytical step. Indirect evidence of the importance of the preanalytical phase stems from the results of several recent studies. In the College of American Pathologists Q-Probe study (11) performed in 660 institutions, a total of 5514 of 114 934 outpatients requisitions (4.8%) were associated with at least one type of order entry error. In 1658 (1.4%) of the requisitions, one or more tests on the requisition were not ordered in the laboratory computer, whereas in 1221 cases (1.1%) at least one test was ordered in the computer that had not appeared on the requisition. A total of 2130 requisitions (1.9%) contained one or more physician name discrepancies between the requisition and the laboratory computer entry, Finally, in 943 requisitions (0.8%), an incorrect test priority was entered for at least one of the requested tests. In an Australian survey on transcription and analytical errors, the transcription error rate was up to 39%, the most frequent types of errors being associated with misidentification of the requested tests, the requesting doctor, and/or the patient. The laboratory with the worst performance had errors in 46% of requests, but even the three best-performing laboratories achieved an error-free reporting of only
85%, with only one achieving 95% (12). Another indirect indicator of the importance of preanalytical processes stems from studies that have demonstrated that the evaluation of specimen adequacy is a critical preanalytical factor affecting test result accuracy and usefulness (13).
Shown in Table 4
are the errors, relative only to the preanalytical phase, detected in the San Raffaele Hospital Laboratory in 1 year. All the preanalytical problems that prevented us from reporting a result were automatically collected and divided by in- and outpatients. The data indicate the number of missing test results attributable to a specific type of preanalytical problem, not the number of problematic samples (e.g., a single hemolyzed tube could have caused the absence of 20 or more results). The difference between in- and outpatients is noteworthy: there were a total of 15 503 errors in 2 583 850 test results (0.60%) for inpatients vs 792 errors in 2 032 133 tests results (0.039%) for outpatients. There are multiple reasons for this difference: (a) direct control of sample drawing for the outpatients vs blood drawing performed by ward personnel, who have a high degree of turnover and lower skill, and (b) the higher complexity of the examinations performed and multiple blood drawings for the inpatients.
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Guidelines for collecting samples and for evaluating submitted specimens are therefore essential because acceptance of improper specimens for analysis may lead to erroneous information that could affect patient care, but only by monitoring on a regular basis the rejected specimens and identifying factors associated with the rejection can we avoid errors and promote continuous quality improvement of laboratory service (14). Moreover, an increasing body of evidence demonstrates the importance of the postanalytical phase for monitoring and improving the TAT (15), for improving the appropriateness of reference intervals (16), and for allowing more objective validation and interpretation of data by use of expert systems (17)(18). Recently, there has been growing interest in implementing and disseminating guidelines for the provision of interpretative comments on laboratory reports (19). To avoid possible errors, this critical activity requires that the laboratory personnel receive adequate training; moreover, there is the need for quality assurance in providing interpretative comments and for auditing this activity (20).
We also paid attention to the area of blood banking. This field is strictly related to laboratory medicine and has very similar working methodologies, which are always being subjected to a very high degree of control because of the high degree of related risk. A report from the College of American Pathologists in collaboration with the CDC Outcomes Working Group (21) describes error stratification in the working process for clinical laboratories similar to the one reported in Table 1
. Of >88 000 defects, 41% were observed in the preanalytical phase of testing, 55% in the postanalytical phase, and only 4% in the analytical phase (21).
Table 2
summarizes a selection of the published reports on errors in transfusion medicine, taking into consideration the effect of the error on the patient. In this case, the essential elements have been extracted: duration of data collection; frequency of misidentification errors; and effect of the error on the patients health. Once again the heterogeneity of the results of the different studies is noteworthy; particularly evident is the very high number of risks of error (4.7% of the transfusions) reported by Baele et al. (22). Point 3 below presents a tentative explanation for this fact.
The heterogeneity of the reported data, in addition to underlining the total lack of a benchmark, the lack of a definition of "maximum allowable error rate", and the lack of a classification of errors, puts in evidence some aspects of critical relevance:
1 error for every 600012 000. This enormous error risk is attributable to the methodology of process analysis adopted by the authors, who reviewed all the transfusions in three University Hospitals in the Brussels area. To our knowledge, this is the only case of systematic analysis of the transfusion process at the bedside, and it shows the very high risk for strictly controlled events such as blood transfusions. The enormous difference in sensitivity of an error detection method based on complaints or fortuitous detection (very low sensitivity) and one based on systematic analysis of all the steps needed to complete the medical act (very high sensitivity) thus is extremely evident. Introducing process analysis in laboratories to identify the error risk related to different procedures is quite advisable (e.g., risk of sample mismatching during blood drawing or during the analytical process).
References
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