Interpretative reports and critical values

Identification methods as a factor affecting the performance of clinical microbiology laboratories participating in an external quality assessment program: a cross-sectional, retrospective analysis

Introduction. Laboratory participation in external quality assessment (EQA) programmes including proficiency testing (PT) is a requirement of clinical laboratory conformance to ISO 15189:2022 Medical laboratories - Requirements for quality and competence. PT is one EQA method whereby laboratories are sent blinded samples for characterization by routine laboratory diagnostic methods. Importantly, PT enables a laboratory's performance to be evaluated in comparison to the standard reference methods and to the performance of other peer laboratories using similar diagnostic methods.Gap statement. The desired outcome of participating in PT is to help laboratories identify possible sources of error in each step of the total testing process and particularly in their test methods during the analytical phase.Aim. This cross-sectional study investigated the impact of using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) compared to conventional phenotypic biochemical testing on laboratory performance in a clinical bacteriology PT scheme.Methodology. During a 6-year period from 2017-2022, the Canadian Microbiology Proficiency Testing implemented 112 PT challenges comprising 22 different sample types and included 61 different bacterial species. This was translated into 5883 graded test events for analysis. Multiple logistic regression techniques were employed to explore the association between the test method employed and laboratory performance. The sample type and aerobic classification of challenge organisms were included as confounding variables.Results. Laboratories using MALDI-TOF MS performed significantly better in characterizing microorganisms than laboratories using phenotypic biochemical testing alone [odds ratio OR = 5.68, confidence interval (CI): 3.92, 8.22] regardless of the sample type and aerobic classification. Notably, our analysis identified a significant association between anaerobic organisms and laboratory performance (OR: 0.24, CI: 0.17-0.35), suggesting that culturing and identifying fastidious organisms remains a significant obstacle for many clinical microbiology laboratories.Conclusions. Although no method is infallible and its performance will depend on the validation and quality assurance procedures, this finding may help the management in the decision for implementing MALDI-TOF MS in the microbiology laboratory. This study highlights the important role PT providers play in the objective assessment of laboratory performance and how it can provide evidence for quality improvement.

Potentials and pitfalls of ChatGPT and natural-language artificial intelligence models for the understanding of laboratory medicine test results. An assessment by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group on Artificial Intelligence (WG-AI)

OBJECTIVES

ChatGPT, a tool based on natural language processing (NLP), is on everyone's mind, and several potential applications in healthcare have been already proposed. However, since the ability of this tool to interpret laboratory test results has not yet been tested, the EFLM Working group on Artificial Intelligence (WG-AI) has set itself the task of closing this gap with a systematic approach.

METHODS

WG-AI members generated 10 simulated laboratory reports of common parameters, which were then passed to ChatGPT for interpretation, according to reference intervals (RI) and units, using an optimized prompt. The results were subsequently evaluated independently by all WG-AI members with respect to relevance, correctness, helpfulness and safety.

RESULTS

ChatGPT recognized all laboratory tests, it could detect if they deviated from the RI and gave a test-by-test as well as an overall interpretation. The interpretations were rather superficial, not always correct, and, only in some cases, judged coherently. The magnitude of the deviation from the RI seldom plays a role in the interpretation of laboratory tests, and artificial intelligence (AI) did not make any meaningful suggestion regarding follow-up diagnostics or further procedures in general.

CONCLUSIONS

ChatGPT in its current form, being not specifically trained on medical data or laboratory data in particular, may only be considered a tool capable of interpreting a laboratory report on a test-by-test basis at best, but not on the interpretation of an overall diagnostic picture. Future generations of similar AIs with medical ground truth training data might surely revolutionize current processes in healthcare, despite this implementation is not ready yet.

Gestión del proceso posanalítico en los laboratorios clínicos según los requisitos de la norma ISO 15189:2012. Consideraciones sobre la revisión, notificación y comunicación de los resultados

El objeto de este trabajo es establecer unas consideraciones para facilitar la gestión del proceso posanalítico respecto a la revisión, notificación y comunicación de los resultados, de acuerdo con los requisitos de la Norma UNE-EN ISO 15189:2013. El ámbito de aplicación incluye las actividades del proceso posanalítico del laboratorio clínico, así como el personal implicado en él (dirección y personal del laboratorio). Se indican los criterios y la información necesaria para realizar la revisión y validación de los resultados de las pruebas analíticas y así enviar a los destinatarios informes claros, asegurando siempre una transcripción fidedigna de los resultados e incluyendo toda la información necesaria para su correcta interpretación. Asimismo, se describen los requisitos para una correcta comunicación de los resultados del laboratorio, haciendo especial hincapié en la comunicación de aquellos resultados alarmantes o críticos. En algunos países de Europa es obligatoria la acreditación, total o parcial, de los laboratorios clínicos, siguiendo la Norma ISO 15189 y esta parece ser la hoja de ruta marcada en otros muchos países. Por ello, es indispensable la comprensión de sus requisitos para realizar una implementación progresiva y más fácil.

Management of postanalytical processes in the clinical laboratory according to ISO 15189:2012 Standard requirements: considerations on the review, reporting and release of results

The objective of this paper is to share some considerations about the management of postanalytical processes in relation to the review, reporting and release of test results in accordance with UNE-EN ISO 15189:2013 Standard requirements. The scope of this paper includes postanalytical activities and the personnel involved (laboratory management and staff). We describe the criteria and information required to review and validate analytical results and ensure that clear reports are sent to requesters. These criteria also guarantee that results are transcribed in a reliable way and that all necessary information is provided for the correct interpretation of results. Likewise, the requirements for the correct release of laboratory results are described, with special emphasis on the release of alarming or critical results. In some European countries, clinical laboratories are required to hold partial or full ISO 15189 accreditation, which is a global trend. Therefore, understanding ISO 15189 requirements is imperative for a progressive and more effective implementation of the Standard.

Predictive accuracy of serum total calcium for both critically high and critically low ionized calcium in critical illness

BACKGROUND

The accuracy of total calcium and its corrected value for predicting critically high and critically low ionized calcium in critical illness is controversial. The aim of this study was to investigate whether the concentration of total serum calcium, either corrected for albumin or not, could predict critically high or low values in critical illness.

METHODS

This report describes a retrospective study using the Medical Information Mart for Intensive Care (MIMIC) III database. Test panels that contained serum albumin, total calcium, and ionized calcium (named ATI panels) with order time intervals of less than one hour were extracted. The predictive accuracy of total calcium, either corrected for albumin or not, was assessed using receiver operating characteristic (ROC) curve analysis.

RESULTS

A total of 12 118 ATIs with 103 critically low and 92 critically high ionized calcium results were extracted. The areas under ROC curves (AUCs) of corrected and uncorrected total calcium for predicting critically low ionized calcium were 0.69 (95% CI: 0.61-0.76) and 0.70 (95% CI: 0.63-0.78), respectively. For predicting critically high ionized calcium, the AUCs were 0.98 (95% CI: 0.97-1.00) and 0.97 (95% CI: 0.95-1.00), respectively. With positive predictive values (PPVs) of 0.05 and 0.10, the sensitivities (both corrected and uncorrected) were approximately 0.50 for predicting critically low ionized calcium and 0.95 for predicting critically high ionized calcium.

CONCLUSIONS

Total calcium, either corrected for albumin or not, is not a reliable test to predict critically low ionized calcium in critical illness. Total calcium's predictive accuracy for critically high ionized calcium is high.

Effect of Harm Anchors in Visual Displays of Test Results on Patient Perceptions of Urgency About Near-Normal Values: Experimental Study

Background

Patient-facing displays of laboratory test results typically provide patients with one reference point (the “standard range”).

Objective

To test the effect of including an additional harm anchor reference point in visual displays of laboratory test results, which indicates how far outside of the standard range values would need to be in order to suggest substantial patient risk.

Methods

Using a demographically diverse, online sample, we compared the reactions of 1618 adults in the United States who viewed visual line displays that included both standard range and harm anchor reference points (“Many doctors are not concerned until here”) to displays that included either (1) only a standard range, (2) standard range plus evaluative categories (eg, “borderline high”), or (3) a color gradient showing degree of deviation from the standard range.

Results

Providing the harm anchor reference point significantly reduced perceived urgency of close-to-normal alanine aminotransferase and creatinine results (P values <.001) but not generally for platelet count results. Notably, display type did not significantly alter perceptions of more extreme results in potentially harmful ranges. Harm anchors also substantially reduced the number of participants who wanted to contact their doctor urgently or go to the hospital about these test results.

Conclusions

Presenting patients with evaluative cues regarding when test results become clinically concerning can reduce the perceived urgency of out-of-range results that do not require immediate clinical action.

Prevalence and Clinical Utility of "Incidental" Critical Values Resulting From Critical Care Laboratory Testing

OBJECTIVE

Panels of clinical laboratory testing may generate "incidental" critical values from unordered parameters. Existing regulations do not clearly delineate guidelines for handling incidental critical values. The objective of this study was to examine the patterns and clinical utility of incidental critical values at 2 critical care laboratories within an academic medical center.

METHODS

In this retrospective study, the electronic health record and laboratory information system were reviewed for incidental critical results obtained from blood gas analyzer analysis of whole blood specimens between November 2010 and August 2014.

RESULTS

Within the retrospective time period, 9,092 incidental critical results were documented, of which only 11.8% were added to the "parent" order following clinical notification. Incidental critical results frequently occurred in patients who had recent critical values for the same parameter.

CONCLUSION

In this study, at an academic medical center, incidental critical values associated with blood gas analyzers were added on at a low rate and often provided redundant information. Relative to the manual effort involved in care providers' notification and documentation of results, incidental critical values appear to have low clinical utility.

Assuring the quality of interpretative comments in clinical chemistry

The provision of interpretative advice on laboratory results is a post-analytic activity and an integral part of clinical laboratory services. It is valued by healthcare workers and has the potential to prevent or reduce errors and improve patient outcomes. It is important to ensure that interpretative comments provided by laboratory personnel are of high quality: comments should be patient-focused and answer the implicit or explicit question raised by the requesting clinician. Comment providers need to be adequately trained and qualified and be able to demonstrate their proficiency to provide advice on laboratory reports. External quality assessment (EQA) schemes can play a part in assessing and demonstrating the competence of such laboratory staff and have an important role in their education and continuing professional development. A standard structure is proposed for EQA schemes for interpretative comments in clinical chemistry, which addresses the scope and method of assessment including nomenclature and marking scales. There is a need for evidence that participation in an EQA program for interpretative commenting facilitates improved quality of comments. It is proposed that standardizing goals and methods of assessment as well as nomenclature and marking scales may help accumulate evidence to demonstrate the impact of participation in EQA for interpretative commenting on patient outcome.

What Alert Thresholds Should Be Used to Identify Critical Risk Results: A Systematic Review of the Evidence

BACKGROUND

Pathology laboratories are required to immediately report results which indicate a patient is at critical risk, but there is little consensus about what values are deemed critical. The aim of this review was to systematically review the literature on alert thresholds for common chemistry and hematology tests in adults and to provide an explicit and ranked source of this evidence.

METHODS

The literature search covered the period of 1995–2014. Evidence sources were critically appraised and ranked using the 1999 Stockholm hierarchy for analytical performance specifications in laboratory medicine modified for establishing decision limits.

RESULTS

The 30 most frequently reported laboratory tests with alert thresholds are presented with evidence rankings. Similar thresholds were reported in North America, Europe and Asia. Seventy percent of papers reported thresholds set by individual institutions, while 18% contained thresholds from surveys of laboratories or clinicians. Forty-six percent of the papers referred to 1 or both of the 2 American laboratory surveys from the early 1990s. “Starter sets” of alert thresholds were recommended by 6 professional bodies, 3 of which were collaborations between pathologists and clinicians. None of the 9 outcome studies identified dealt with confounding factors.

CONCLUSIONS

Recommendations by professional bodies based on outdated surveys of the former state of the art or consensus are currently the best sources of evidence for laboratories to build their alert list. Well-designed outcome studies and greater collaboration between clinicians and the laboratory are needed to identify the most appropriate alert thresholds that signify actionable, critical or significant risk to patient well-being.

R.A.P.I.D. (Root Aggregated Prioritized Information Display): A single screen display for efficient digital triaging of medical reports

OBJECTIVE

The timely acknowledgement of critical patient clinical reports is vital for the delivery of safe patient care. With current EHR systems, critical reports reside on different screens. This leads to treatment delays and inefficient work flows. As a remedy, the R.A.P.I.D. (Root Aggregated Prioritized Information Display) system represents all data on a single screen, and its simple and intuitive "button" array structure allows triaged sign-off/sign-out of critical and non-critical reports.

MATERIALS AND METHODS

With 100 hematology and chemistry reports from each of two EHR systems Meditech (Westwood, MA) and Orchard Labs, Inc. (Carmel, IN), we generated files of the reports in their individual standard display formats (enhanced Meditech-EM and enhanced Orchard-EO). We also displayed the same 200 reports in the R.A.P.I.D.

FORMAT

We then conducted a randomized trial to compare the time and accuracy of acknowledgement of critical and non-critical results.

RESULTS

The sign-off times for reviewing the results for physician and non-physician providers, respectively, in seconds (with 95% confidence intervals) were for EM 1.78 (1.40-2.26) and 1.99 (1.72-2.30), for EO 2.69 (2.12-3.42) and 2.78 (2.40-3.21), and for R.A.P.I.D. 0.83 (0.70-0.98) and 1.58 (1.43-1.76). Non-physician providers reassigned system-defined non-critical results as critical with a frequency of 15.2% for EM, 18.4% for EO, and 7.83% for R.A.P.I.D., and critical results as non-critical with a frequency of 14.7%, 5.6%, and 5.8% respectively.

DISCUSSION

The new display system was superior to two standard EHR systems that were significantly enhanced by first collecting the reports from their usual distributed locations and then by creating for each of the two standard EHRs a single file of reports for acknowledgement.

CONCLUSIONS

From a single screen display of all reports, the new display system enables timely acknowledgement of critical reports for patient safety and non-critical report triage for improved provider work flows.

Croatian survey on critical results reporting

INTRODUCTION

Poor harmonization of critical results management is present in various laboratories and countries, including Croatia. We aimed to investigate procedures used in critical results reporting in Croatian medical biochemistry laboratories (MBLs).

MATERIALS AND METHODS

An anonymous questionnaire, consisting of 24 questions/statements, related to critical results reporting procedures, was send to managers of MBLs in Croatia. Participants were asked to declare the frequency of performing procedures and degree of agreement with statements about critical values reporting using a Likert scale. Total score and mean scores for corresponding separate statements divided according to health care setting were calculated and compared.

RESULTS

Responses from 111 Croatian laboratories (48%) were analyzed. General practice laboratories (GPLs) more often re-analyzed the sample before reporting the critical result in comparison with the hospital laboratories (HLs) (score: 4.86 (4.75-4.96) vs. 4.49 (4.25-4.72); P=0.001) and more often reported the critical value exclusively to the responsible physician compared to HLs (4.46 (4.29-4.64) vs. 3.76 (3.48-4.03), P<0.001). High total score (4.69 (4.56-4.82)) was observed for selection of the critical results list issued by the Croatian Chamber of Medical Biochemistry (CCMB) indicating a high harmonization level for this aspect of critical result management. Low total scores were observed for the statements regarding data recording and documentation of critical result notification.

CONCLUSIONS

Differences in practices about critical results reporting between HLs and GPLs were found. The homogeneity of least favorable responses detected for data recording and documentation of critical results notification reflects the lack of specific national recommendations.

Establishing an evidence base for critical laboratory value thresholds

OBJECTIVES

Critical values denote laboratory test results indicating a life-threatening situation. The outcomes of this premise have not been rigorously evaluated.

METHODS

Five years of inpatient admissions were examined for critical or "near-critical" results (total admissions = 165,066; total test results = 872,503). In-hospital mortality was examined as a function of time and degree of test result abnormality.

RESULTS

Some critical value thresholds appropriately identified patients at risk for death (eg, elevated potassium). Other thresholds were too conservative (elevated hematocrit, hemoglobin) or not conservative enough (elevated lactate). Mortality risk for most critical values was time dependent, but some critical values showed no temporal effect on mortality (elevated activated partial thromboplastin time [APTT], international normalized ratio [INR], and glucose). Following an initial critical result, further worsening was associated with increased mortality. Prior hospital admission within 30 days was a predictor of lower mortality for some (elevated APTT, INR, potassium, and sodium; low glucose, hematocrit, hemoglobin, and potassium) but not other critical values (elevated lactate, glucose, hematocrit, and hemoglobin; low sodium).

CONCLUSIONS

Only a subset of laboratory critical value thresholds was optimally chosen for increased risk of in-hospital mortality, with a time urgency for most but not all critical values. For many tests, a prior hospital admission imparted a decreased risk of in-hospital death.

Study of variables affecting critical value notification in a laboratory catering to tertiary care hospital

During post-analytical phase, critical value notification to responsible caregiver in a timely manner has potential to improve patient safety which requires cooperative efforts between laboratory personnel and caregivers. It is widely accepted by hospital accreditors that ineffective notification can lead to diagnostic errors that potentially harm patients and are preventable. The objective of the study was to assess the variables affecting critical value notification, their role in affecting it's quality and approaches to improve it. In the present study 1,187 critical values were analysed in the Clinical Chemistry Laboratory catering to tertiary care hospital for neuropsychiatric diseases. During 25 months of study period, we evaluated critical value notification with respect to clinical care area, caregiver to whom it was notified and timeliness of notification. During the study period (25 months), the laboratory obtained 1,279 critical values in clinical chemistry. The analytes most commonly notified were sodium and potassium (20.97 & 20.8 % of total critical results). Analysis of critical value notification versus area of care showed that critical value notification was high in ICU and emergency area followed by inpatients and 64.61 % critical values were notified between 30 and 120 min after receiving the samples. It was found that failure to notify the responsible caregiver in timely manner represent an important patient safety issue and may lead to diagnostic errors. The major area of concern are notification of critical value for outpatient samples, incompleteness of test requisition forms regarding illegible writing, lack of information of treating physician and location of test ordering and difficulty in contacting the responsible caregiver.

Patient safety & post-analytical error

Post-analytical laboratory processes have been considered to be less prone to error than preanalytical processes because of the widespread adoption of laboratory automation and interfaced laboratory reporting. Quality monitors and controls for the post-analytical process have focused on critical result notification, meeting established turnaround time goals, and review of changed reports. The rapid increase in the adoption of electronic health records has created a new role for laboratory professionals in the management of patient test results. Laboratory professionals must interface with the clinical side of the health care team in establishing quality control for post-analytical processes, particularly in high-risk transitions of care.

Alert value reporting: a new strategy for patient safety

OBJECTIVES

The objectives of this study are to introduce the "alert value reporting" concept in primary care setting, to propose a list of chemistry and hematology alert limit tests that can be chosen for that strategy, to show how this notification procedure can be designed and established, and finally to evaluate the effectiveness and physicians' satisfaction regarding the proposed approach. In contrast to critical value reporting, alert value reporting would not allude to a result that may imply a life-threatening situation, but would indicate that an early diagnostic/therapeutic action would improve the patient's management and quality of life.

DESIGN AND METHODS

A list of chemistry and hematology alert limit tests to be used for the strategy was agreed upon between laboratory professionals and general practitioners. Next, a retrospective 12-month study involving more than 1 million laboratory tests was made to check how many of these alert values would have been communicated if these theoretical alert values had been applied. A prospective analysis of every reported alert value during 6 months was carried out to assess the intervention effectiveness and the requesting physician's satisfaction with the new strategy.

RESULTS

The alert value reporting was successfully executed. 20% of the reported alert values motivated the decision to reschedule the next patient's appointment. 90% of physicians considered alert value reporting as an interesting strategy to be continued.

CONCLUSIONS

Alert value reporting strategy motivated changes in patient's management. Further studies are needed to test if this approach can contribute to enhance patient safety and decision-making.

Heterogeneity of publicly accessible online critical values for therapeutic drugs

Introduction:

Critical values are reported to clinicians when laboratory values are life threatening and require immediate attention. To date no definitive critical value limit recommendations have been produced regarding therapeutic drug monitoring. Some laboratories choose to publish critical value lists online. These publicly available values may be accessed and potentially utilized by laboratory staff, patient care providers, and patients.

Materials and Methods:

A web-based search of laboratories associated with the Accreditation Council for Graduate Medical Education pathology residency programs was initiated to determine which therapeutic drugs had critical values and to examine the degree of variation in published critical values for these institutions.

Results:

Of the 107 institutions with university-based pathology training programs, 36 had published critical values online for review. Thirteen therapeutic drugs were investigated and the number of institutions reporting critical value limits for the drug, as well as the median, range, standard deviation, and the coefficient of variation of critical value concentration limits for each drug were determined. A number of the online critical value limits were deemed to be erroneous, most likely due to incorrectly listed units of measurement.

Conclusions:

There was a large degree of heterogeneity with regard to the chosen critical value limits for therapeutic drugs. This wide variance in critical values appears to be greater than that observed in interassay proficiency testing. Institutions should reexamine the rationale for their current critical value parameters and ensure that critical value limits and associated units are accurately published online.

Direct-to-consumer testing: more risks than opportunities

As a result of incessant genetic discoveries and remarkable technological advancements, the availability and the consequent consumer's request for genetic testing are growing exponentially, leading to the development of a 'parallel' market, i.e. the direct-to-consumer (DTC) testing, also known as 'direct access testing' (DAT). Analogous to the traditional laboratory diagnostics, drawbacks of DTC testing might arise from any step characterising the total testing process, and include poor control of both appropriateness and preanalytical requirements, potential operation outside national or international regulation for in vitro diagnostic testing, little evidence of quality as well as the risk of transfer of genetic materials from the companies to other entities. Another important issue is the test panels offered to consumers, which are often based on preliminary, speculative or unsupported scientific information. Finally, the potential of this type of testing to generate anxiety or false reassurance should also be carefully considered. Although DTC testing carries some theoretical advantages (e.g. greater consumer autonomy and empowerment), solid clinical studies and costs vs. benefit analyses are needed to definitely establish whether DTC testing might be effective for decreasing the burden of diseases, delay their onset or modify their progression and therefore the clinical outcome.

Quality in Surgical Pathology Communication and Reporting

Context.—Communication in surgical pathology is complex and includes multiple facets.

Objective.—To discuss different aspects of pathology practice that represent quality communication in surgical pathology.

Data Sources.—Literature review.

Conclusions.—Achieving quality communication in surgical pathology is dependent on pathologists addressing multiple situations including managing physicians' expectations for turnaround time and ancillary testing, understanding what information is needed to manage the patient at intraoperative consultation and in the final report, assuring adequate report content with the use of synoptic checklist reports, and using report formatting suggestions that aid report comprehension. Finally, the pathologists' availability to answer questions and discuss cases is an important factor in effective communication, including their willingness to verbally report urgent and significant unexpected diagnoses to ensure that important diagnoses are not overlooked.

Effect of pre-analytical errors on quality of laboratory medicine at a neuropsychiatry institute in north India

Advances in instrument technology and automation have simplified tasks in laboratory diagnostics reducing errors during analysis thereby improving the quality of test results. However studies show that most laboratory errors occur in the pre-analytical phase. In view of the paucity of studies examining pre-analytical errors, we examined a total of 1513 request forms received at our laboratory during a 3 month period. The forms were scrutinized for the presence of specific parameters to assess the pre-analytical errors affecting the laboratory results. No diagnosis was provided on 61.20% of forms. Type of specimen was not mentioned in 61.60% of the forms and 89.25% of all forms were illegible. Critical results were encountered in 17.30% of patients, and of these 76.60% were not communicated due to incomplete forms. Thus, by following standard operating procedures vigorously from patient preparation to sample processing the laboratory results can be significantly improved without any extra cost.

The detection and prevention of errors in laboratory medicine

The last few decades have seen a significant decrease in the rates of analytical errors in clinical laboratories. Evidence demonstrates that pre- and post-analytical steps of the total testing process (TTP) are more error-prone than the analytical phase. Most errors are identified in pre-pre-analytic and post-post-analytic steps outside of the laboratory. In a patient-centred approach to the delivery of health-care services, there is the need to investigate, in the TTP, any possible defect that may have a negative impact on the patient. In the interests of patients, any direct or indirect negative consequence related to a laboratory test must be considered, irrespective of which step is involved and whether the error depends on a laboratory professional (e.g. calibration/testing error) or non-laboratory operator (e.g. inappropriate test request, error in patient identification and/or blood collection). Patient misidentification and problems communicating results, which affect the delivery of diagnostic services, are recognized as the main goals for quality improvement. International initiatives aim at improving these aspects. Grading laboratory errors on the basis of their seriousness should help identify priorities for quality improvement and encourage a focus on corrective/preventive actions. It is important to consider not only the actual patient harm sustained but also the potential worst-case outcome if such an error were to reoccur. The most important lessons we have learned are that system theory also applies to laboratory testing and that errors and injuries can be prevented by redesigning systems that render it difficult for all health-care professionals to make mistakes.