Is it Necessary to Repeat Critical Values in the Laboratory?

An appraisal of the practice of duplicate testing for the detection of irregular analytical errors

OBJECTIVES

Our study aimed to determine the usefulness of duplicate testing in identifying irregular analytical errors and subsequent prevention of patient mismanagement.

METHODS

In our laboratory, all requests for Na+, Ca2+, alkaline phosphatase (ALP), and high-sensitivity cardiac-troponin-I (hs-cTnI) are run in duplicate. Data from four separate weeks for Na+ (n=21,649), Ca2+ (n=14,803) and ALP (n=19,698); and a full year for hs-cTnI (n=17,036) were gathered. For each test, pre-defined limits for differences between duplicates were used to identify erroneous results (Fliers). We further characterised a subset of such fliers as "critical errors", where duplicates fell on opposing sides of a reference/decision making threshold. The costs/benefits of running these tests in duplicate were then considered in light of increased number of tests analysed by this approach.

RESULTS

For Na+, 0.03 % of duplicates met our flier defining criteria, and 0.01 % of specimens were considered critical errors. For Ca2+ requests, 4.58 % of results met our flier defining criteria and 0.84 % were critical errors. For ALP, 0.22 % of results were fliers, and 0.01 % were critical errors. For hs-cTnI, 1.58 % of results were classified as fliers, whilst 0.14 % were classified as a critical error. Depending on the test in question, running all analyses in duplicate increased annual costs by as little as €1,100 (for sodium), and as much as €48,000 (for hs-cTnI).

CONCLUSIONS

Duplicate testing is effective at identifying and mitigating irregular laboratory errors, and is best suited for assays predisposed to such error, where costs are minimal, and clinical significance of an incorrect result can justify the practice.

Hiding in Plain Sight: The Issue of Hidden Variables

Here we discuss "hidden variables", which are typically introduced during an experiment as a consequence of the application of two independent variables together to create a stimulus. With increased sophistication in modern chemical biology tools and related precision interrogation techniques, hidden variables have become integral to many chemical biologists' routine experiments. For instance, they can appear in the use of light-activatable chemical probes (e.g., μMap, T-REX), or stimulus-induced enzyme activation (e.g., APEX). Unfortunately, control experiments assess only how independent variables affect measured outcomes and not the multiple differences between the two independent variables and the twain. We outline ways to account for potential hidden variables in experimental design and data interpretation as a means to aid developers of new methods, particularly those involving light-driven techniques, chemical activation, or biorthogonal chemistries, to better incorporate well-controlled procedures.

Termination of Repeat Testing in Chemical Laboratories Based on Practice Guidelines: Examining the Effect of Rule-Based Repeat Testing in a Transplantation Center

BACKGROUND

Although the automation of instruments has reduced the variability of results and errors of analysis, in some laboratories, repeating a test to confirm its accuracy is still performed for critical and noncritical results. However, the importance of repeat testing is not well established yet, and there are no clear criteria for repeating a test.

MATERIALS AND METHODS

In this cross-sectional study, all repeated tests for 26 biochemical analytes (i.e., albumin, alkaline phosphatase (ALP), alanine aminotransferase (ALT), amylase, aspartate aminotransferase (AST), bilirubin total (BT), bilirubin direct (BD), blood urea nitrogen (BUN), calcium, chloride (Cl), cholesterol total (CholT), creatine kinase (CK), creatinine (Cr), glucose, gamma-glutamyl transferase (GGT), high-density lipoprotein-cholesterol (HDL-c), iron, lactate dehydrogenase (LDH), LDL-c, lipase, magnesium (Mg), phosphorus (Ph), protein total (ProtT), total iron binding capacity (TIBC), triglyceride (TG), and uric acid) were assessed in both critical and noncritical ranges over two consecutive months (routine subjective test repeats in the first month and rule-based repeats in the second month). To determine the usefulness of test repeats, differences between the initial and verified results were compared with the allowable bias, and repeat testing was considered necessary if it exceeded the allowable bias range. All causes of repeat testing, including linearity flags, delta checks, clinically significant values, and critical values, were also documented. All data, including the cause of repeats, initial and verified results, time, and costs in the two consecutive months, were transferred to Microsoft Excel for analysis. For comparison of data between the months, Student's t-test was used.

RESULTS

A total of 7714 repeat tests were performed over two consecutive months. Although a significant decline (38%) was found in repeated tests in the second month (P < 0.001), there was no significant change in the percentage of unnecessary repeats (77% in the first month and 74% in the second month). In both consecutive months, AST and ALT were the most commonly repeated tests, and delta check was the most common cause of repeat testing. Mg, ALP, AST, and lipase showed the highest rates of necessary repeats, respectively (the least stable tests), while albumin, LDL, and CholT tests showed the highest rates of unnecessary repeats, respectively (the most stable tests). The total cost and delay in turnaround time (TAT) due to repeated testing decreased by 32% and 36%, respectively.

CONCLUSION

Although repeat testing has been shown to be unnecessary in most cases, having a strict policy for repeat testing appears to be more valuable than avoiding it completely. Each laboratory is advised to establish its own protocol for repeat testing based on its own practice.

Critical Value Reporting at Egyptian Laboratories

OBJECTIVES

To examine critical value reporting policies and practices and to identify critical value ranges for selected common laboratory assays at inpatient division of laboratories of Alexandria hospitals.

METHODS

A cross-sectional descriptive study design was used. Subjects were from inpatient division of all laboratories of Alexandria hospitals (40 laboratories). Data were collected using a questionnaire composed of 4 sections. The first section explored hospital and laboratory characteristics. The second section assessed policies and procedures of critical value reporting. The third section explored the reporting process. The fourth section explored critical value ranges for selected common laboratory assays.

RESULTS

Written procedure for reporting of critical values was present in 77.5% of laboratories and a comprehensive list of critical values in 72.55%. For laboratories having a critical value list, the number of tests in the list ranged from 7 to 40. Three-fifths of laboratories had a policy for assessing the timeliness of reporting and 3 quarters stated that the laboratory policy requires feedback (60.0% and 75.0%, respectively). The hospital laboratory physician was responsible for critical value reporting followed by the laboratory technician (75.0% and 50.0%, respectively). The call is received mainly by nurses and physicians ordering the test (67.5% and 55.0%, respectively) and the channel of reporting is mainly the telephone or through sending test report to the ward (67.5% and 50.0%, respectively). Wireless technologies are used in reporting in only 10.0% of hospitals. The cutoff limits for reporting different assays showed considerable interlaboratory variation.

CONCLUSIONS

Critical value policies and practices showed interinstitutional variation with deficiencies in some reporting practices. Selection of critical assays for notification and setting the limits of notification exhibited wide variation as well.

Post-analytical laboratory work: national recommendations from the Working Group for Post-analytics on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine

The post-analytical phase is the final phase of the total testing process and involves evaluation of laboratory test results; release of test results in a timely manner to appropriate individuals, particularly critical results; and modification, annotation or revocation of results as necessary to support clinical decision-making. Here we present a series of recommendations for post-analytical best practices, tailored to medical biochemistry laboratories in Croatia, which are intended to ensure alignment with national and international norms and guidelines. Implementation of the national recommendations is illustrated through several examples.

Errors in the Extra-Analytical Phases of Clinical Chemistry Laboratory Testing

The total testing process consists of various phases from the pre-preanalytical to the post-postanalytical phase, the so-called brain-to-brain loop. With improvements in analytical techniques and efficient quality control programmes, most laboratory errors now occur in the extra-analytical phases. There has been recent interest in these errors with numerous publications highlighting their effect on service delivery, patient care and cost. This interest has led to the formation of various working groups whose mission is to develop standardized quality indicators which can be used to measure the performance of service of these phases. This will eventually lead to the development of external quality assessment schemes to monitor these phases in agreement with ISO15189:2012 recommendations. This review focuses on potential errors in the extra-analytical phases of clinical chemistry laboratory testing, some of the studies performed to assess the severity and impact of these errors and processes that are in place to address these errors. The aim of this review is to highlight the importance of these errors for the requesting clinician.

Repeating Critical Hematology and Coagulation Values Wastes Resources, Lengthens Turnaround Time, and Delays Clinical Action

OBJECTIVES

To determine the need and impact of repeating critical values in hematology and coagulation.

METHODS

We prospectively evaluated the need for repeating critical values. The cost of this practice was estimated using a workflow analysis. Retrospective chart review before and after removal of this process was performed to assess the clinical impact of removing this practice.

RESULTS

Over 95% of the repeated values remained critical and all but one of the repeats were within the expected analytical precision of the assays. The practice of repeating critical values delayed turnaround time for these results and wasted resources, most notably manpower. The delay associated with repeating hematology critical values resulted in delayed administration of blood product (RBC units).

CONCLUSIONS

Repeating critical hematology and coagulation results was found to be an unnecessary process that wasted laboratory resources and lengthened turnaround time, delaying clinical intervention.

Standardization of haematology critical results management in adults: an International Council for Standardization in Haematology, ICSH, survey and recommendations

INTRODUCTION

These recommendations are intended to develop a consensus in the previously published papers as to which parameters and what values should be considered critical. A practical guide on the standardization of critical results management in haematology laboratories would be beneficial as part of good laboratory and clinical practice and for use by laboratory-accrediting agencies.

METHODS

A working group with members from Europe, America, Australasia and Asia was formed by International Council for Standardization in Haematology. A pattern of practice survey of 21 questions was distributed in 2014, and the data were collected electronically by Survey Monkey. The mode, or most commonly occurring value, was selected as the threshold for the upper and lower alert limits for critical results reporting.

RESULTS

A total of 666 laboratories submitted data to this study and, of these, 499 submitted complete responses. Full blood count critical results alert thresholds, morphology findings that trigger critical result notification, critical results alert list, notification process and maintenance of critical results management protocol are described. This international survey provided a snapshot of the current practice worldwide and has identified the existence of considerable heterogeneity of critical results management.

CONCLUSION

The recommendations in this study represent a consensus of good laboratory practice. They are intended to encourage the implementation of a standardized critical results management protocol in the laboratory.

The impact of repeat-testing of common chemistry analytes at critical concentrations

BACKGROUND

Early notification of critical values by the clinical laboratory to the treating physician is a requirement for accreditation and is essential for effective patient management. Many laboratories automatically repeat a critical value before reporting it to prevent possible misdiagnosis. Given today's advanced instrumentation and quality assurance practices, we questioned the validity of this approach. We performed an audit of repeat-testing in our laboratory to assess for significant differences between initial and repeated test results, estimate the delay caused by repeat-testing and to quantify the cost of repeating these assays.

METHODS

A retrospective audit of repeat-tests for sodium, potassium, calcium and magnesium in the first quarter of 2013 at Tygerberg Academic Laboratory was conducted. Data on the initial and repeat-test values and the time that they were performed was extracted from our laboratory information system. The Clinical Laboratory Improvement Amendment criteria for allowable error were employed to assess for significant difference between results.

RESULTS

A total of 2308 repeated tests were studied. There was no significant difference in 2291 (99.3%) of the samples. The average delay ranged from 35 min for magnesium to 42 min for sodium and calcium. At least 2.9% of laboratory running costs for the analytes was spent on repeating them.

CONCLUSIONS

The practice of repeating a critical test result appears unnecessary as it yields similar results, delays notification to the treating clinician and increases laboratory running costs.

Utility of repeat testing of critical values: a Q-probes analysis of 86 clinical laboratories

CONTEXT

A common laboratory practice is to repeat critical values before reporting the test results to the clinical care provider. This may be an unnecessary step that delays the reporting of critical test results without adding value to the accuracy of the test result.

OBJECTIVES

To determine the proportions of repeated chemistry and hematology critical values that differ significantly from the original value as defined by the participating laboratory, to determine the threshold differences defined by the laboratory as clinically significant, and to determine the additional time required to analyze the repeat test.

DESIGN

Participants prospectively reviewed critical test results for 4 laboratory tests: glucose, potassium, white blood cell count, and platelet count. Participants reported the following information: initial and repeated test result; time initial and repeat results were first known to laboratory staff; critical result notification time; if the repeat result was still a critical result; if the repeat result was significantly different from the initial result, as judged by the laboratory professional or policy; significant difference threshold, as defined by the laboratory; the make and model of the instrument used for primary and repeat testing.

RESULTS

Routine, repeat analysis of critical values is a common practice. Most laboratories did not formally define a significant difference between repeat results. Repeated results were rarely considered significantly different. Median repeated times were at least 17 to 21 minutes for 10% of laboratories. Twenty percent of laboratories reported at least 1 incident in the last calendar year of delayed result reporting that clinicians indicated had adversely affected patient care.

CONCLUSION

Routine repeat analysis of automated chemistry and hematology critical values is unlikely to be clinically useful and may adversely affect patient care.

Critical values in hematology

INTRODUCTION

Critical values are life-threatening results that require immediate notification to the patient's healthcare provider. Accreditation bodies require laboratories to establish critical values. A survey of Ontario laboratories was conducted to determine current practice for critical values in hematology.

METHODS

The survey was sent to 182 participants questioning sources for establishing critical values, levels, review frequency, delta checks, and reporting. The survey was completed by laboratory managers, supervisors, technical specialists, senior technologists, and bench technologists working in hematology.

RESULTS

The majority of participating laboratories have established critical values limits for hemoglobin, leukocyte counts, and platelet counts. Most laboratories also include the presence of malaria parasites and blast cells. Some laboratories reported the presence of plasma cells, sickle cells, schistocytes, and spherocytes as critical values. Multiple sources are used for establishing a critical value policy. There was variability for the frequency of critical values review. Rules may differ for a first-time patient sample vs. a repeat patient sample. Delta checks are seldom used to determine whether a result should be called a critical value. Most participants require the individual taking the critical result(s) to read back and confirm that they are directly involved with the patient's care.

CONCLUSION

There is a lack of consensus for critical values reporting in hematology. As critical value reporting is crucial for patient safety, standardization of this practice would be beneficial.

Utility and necessity of repeat testing of critical values in the clinical chemistry laboratory

CONTEXT

Routine repeat testing of critical values is a long-standing practice in many clinical laboratories; however, its usefulness and necessity remain to be empirically established and no regulatory requirements yet exist for verification of the critical value results obtained by repeat analysis.

OBJECTIVE

To determine whether repeat testing of critical values is useful and necessary in a clinical chemistry laboratory.

METHODS

A total of 601 chemistry critical values (potassium, n = 255; sodium, n = 132; calcium, n = 108; glucose, n = 106) obtained from 72,259 routine clinical chemistry specimens were repeat tested. The absolute value and the percentage of difference between the two testing runs were calculated for each of the four critical values and then compared with the allowable error limit put forth in the College of American Pathologists (CAP).

RESULTS

Among the repeat data for the 601 critical values, a total of 24 showed large differences between the initial result and the repeated result which exceeded the CAP limits for allowable error. The number and rates (%) of large differences for within and outside the analytical measurement range (AMR) were 12 (2.1%) and 12 (41.4%), respectively. For the 572 critical values within the AMR for each test category, the mean absolute difference (mmol/L) and difference(%) between the two testing runs were: potassium, 0.1 mmol/L (2.7%); sodium, 2.1 mmol/L (1.7%); calcium, 0.05 mmol/L (3.0%); glucose, 0.18 mmol/L (2.6%).

CONCLUSIONS

When the initial chemistry critical values are within the AMR, repeated testing does not improve accuracy and is therefore unnecessary. When the initial chemistry critical values are outside the AMR, however, the benefit of repeated testing justifies its performance and makes it necessary. Performing repeat clinical testing on a case-by-case, rather than routine, basis can improve patient care by delivering critical values more rapidly while providing savings on reagent costs associated with unnecessary repeat testing.

An examination of the usefulness of repeat testing practices in a large hospital clinical chemistry laboratory

A long-standing practice in clinical laboratories has been to automatically repeat laboratory tests when values trigger automated "repeat rules" in the laboratory information system such as a critical test result. We examined 25,553 repeated laboratory values for 30 common chemistry tests from December 1, 2010, to February 28, 2011, to determine whether this practice is necessary and whether it may be possible to reduce repeat testing to improve efficiency and turnaround time for reporting critical values. An "error" was defined to occur when the difference between the initial and verified values exceeded the College of American Pathologists/Clinical Laboratory Improvement Amendments allowable error limit. The initial values from 2.6% of all repeated tests (668) were errors. Of these 668 errors, only 102 occurred for values within the analytic measurement range. Median delays in reporting critical values owing to repeated testing ranged from 5 (blood gases) to 17 (glucose) minutes.

Does routine repeat testing of critical values offer any advantage over single testing?

CONTEXT

Before being communicated to the caregiver, critical laboratory values are verified by repeat testing to ensure their accuracy and to avoid reporting false or erroneous results.

OBJECTIVE

To determine whether 2 testing runs offered any advantage over a single testing run in ensuring accuracy or in avoiding the reporting of false or erroneous results.

DESIGN

Within the hematology laboratory, 5 tests were selected: hemoglobin level, white blood cell count, platelet count, prothrombin time, and activated partial thromboplastin time. A minimum of 500 consecutive critical laboratory test values were collected retrospectively for each test category. The absolute value and the percentage of change between the 2 testing runs for each critical value were calculated and averaged for each test category and then compared with our laboratory's preset, acceptable tolerance limits for reruns.

RESULTS

The mean results obtained for the absolute value and the percentage of change between the testing runs were 0.08 g/dL (1.4%) for hemoglobin levels, 50 cells/µL (10.2%) for white blood cell counts, 1500 cells/µL (9.9%) for platelet counts, 0.7 seconds (1.4%) for prothrombin time, and 5.1 seconds (4.4%) for activated partial thromboplastin time (all within our laboratory's acceptable tolerance limits for reruns). The percentage of specimens with an absolute value or a mean percentage of change outside our laboratory's acceptable tolerance limits for reruns ranged between 0% and 2.2% among the test categories. No false or erroneous results were identified between the 2 testing runs in any category.

CONCLUSIONS

Routine, repeat testing of critical hemoglobin level, platelet count, white blood cell count, prothrombin time, and activated partial thromboplastin time results did not offer any advantage over a single run.