Interference with serum indices measurement, but not chemical analysis, on the Roche Modular by Patent Blue V

Autoverification-Based Algorithms to Detect Preanalytical Errors: Two Examples

The preanalytical phase of testing accounts for the majority of the errors. Software-based quality rules, such as autoverification, can assist in preanalytical error detection; therefore, preventing erroneous results from being reported. Two autoverification rules, turbidity/lipemia, and pseudohypoglycemia/pseudohyperkalemia alarms, are highlighted. Increased sample turbidity may arise from several causes outside of lipemia. Typically, this can be resolved by clarifying the sample with standard centrifugation. Truly lipemic specimens typically require higher centrifugation speeds and greater centrifugation time. At our facility, 96% of direct bilirubin (DBIL), 95% of aspartate transaminase (AST), and 98% of alanine transaminase (ALT) turbidity/lipemia alarms were found to be from sample turbidity versus lipemia. Secondly, a pseudohypoglycemia/pseudohyperkalemia rule was employed for specimens with delayed separation from cellular material. Of the total potassium results >6.0 mmol/L or glucose results <40 mg/dL (2.2 mmol/L), 30% and 50% respectively were noted to have delayed sample separation.

Frequency of icteric interference in clinical chemistry laboratory tests and causes of severe icterus

Objectives

The aims of this study were to identify the causes of severe icterus in an academic medical center patient population and to assess the impact of icterus on clinical chemistry testing using assay package insert thresholds.

Design

and Methods: In this retrospective study at an academic medical center core clinical laboratory, icteric, hemolysis, and lipemia indices were available for all serum and plasma chemistry specimens analyzed on Roche Diagnostics cobas 8000 analyzers over a 12-month period, encompassing 414,502 specimens from 94,081 unique patients (51,851 females; 42,230 males) including children, inpatient, outpatient, and emergency department patients. Extensive chart review was done for all 57 patients (4 pediatric, 53 adult; 534 total specimens) who had one or more samples with an icteric index of 40 or higher (defined as severe icterus).

Results

Specimen icteric index exceeded package insert icteric index thresholds in 0.14% of clinical chemistry assays, with the highest number of instances for creatinine (1358 samples, 0.6% of total tests), total protein (1194 samples, 2.2%), and ammonia (161 samples, 3.9%). The 57 patients with an icteric index of 40 or higher accounted for 49.7% of all instances where the icteric index exceeded the specific assay package insert limit. The most common etiologies of this group of 57 patients were alcohol-related liver disease (34 patients), biliary tract disease (7 patients), and neoplasms (6 patients).

Conclusions

Approximately half of all instances where specimen icteric index exceeded assay package insert thresholds occurred in a small cohort of patients with severe liver/biliary tract disease.

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Specimen icteric indices exceeded package insert icteric index thresholds for 0.14% of clinical chemistry tests ordered at an academic medical center.

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Icteric interference exceeding package insert thresholds had the most overall occurrences for enzymatic creatinine, total protein, and ammonia.

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Only 57 of 94,081 unique patients (0.06%) with severe icterus accounted for nearly half of instances where the icteric index exceeded the package insert limit for a specific assay.

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The small cohort of patients with severe icterus had high mortality generally associated with cirrhosis, biliary disease, or aggressive metastatic cancer.

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Icteric indices exceeding 20 were mostly comprised of patients with predominantly conjugated hyperbilirubinemia.

Les médicaments qui interfèrent avec les bilans biologiques : revue de la littérature

BACKGROUND

Biological assessment is an integral part of the diagnostic process that guides therapeutic management decisions. However, these analyses remain subject to interference from endogenous or exogenous factors, which may alter the results.

OBJECTIVE

To provide an up-to-date and comprehensive overview of the most commonly documented types of interference attributable to medications, to ensure reliable interpretation of test results and better management of patients.

DATA SOURCES

This comprehensive systematic review of the literature was carried out in 2018. The bibliographic search was carried out in various online databases, specifically PubMed, ScienceDirect and Google Scholar.

STUDY SELECTION

Only publications in French or English concerning medicinal products for human use were retained. The investigators' examination of drug-related interference with laboratory tests was limited to blood assays (serum or plasma).

DATA EXTRACTION

An Excel spreadsheet was used to analyze the results. A total of 82 articles were selected. The interferences studied affected 47 biological parameters corresponding to various types of assessment: hormonal, hepatic, and renal.

DATA SYNTHESIS

The mechanisms reported in the literature identified were analytical (56.9%), physiological (17.82%), and pharmacological (20.11%). The remainder of the mechanisms (5.17%) were not defined.

CONCLUSIONS

Clinicians should be vigilant in validating and interpreting laboratory test results for patients receiving these types of drugs. Dialogue between clinicians and biological scientists is the best way to avoid unnecessary additional testing, which is often cumbersome and costly.

Repeat patient testing-based quality control shows promise for use in veterinary biochemistry testing

BACKGROUND

Repeat patient testing-based quality control (RPT-QC) is a form of statistical QC and an alternative to commercial quality control materials (QCM).

OBJECTIVE

This study investigated the suitability of canine heparinized plasma for use in RPT-QC and assessed the predicted performance of RPT-QC for the detection of analytical error in chemistry testing.

METHODS

The stability of canine plasma for RPT-QC was investigated via storage at two temperatures for three or six time points. Storage data were analyzed using repeated measures ANOVA and by comparing results for stored specimens to baseline data using predetermined criteria. To generate RPT-QC limit-setting and -validation data, leftover plasma was prospectively measured. Once control limits were established, these were challenged by measuring specimens for which the repeat aliquot had been manipulated to mimic analytical error. Finally, the predicted performance of RPT-QC and QCM-QC with four control rules was investigated using Westgard's EZ Rules 3.

RESULTS

Refrigerated storage of canine plasma for 7 days allowed mild changes facilitating RPT-QC. RPT-QC limits for 12 of 17 common measurands were validated. Validated limits successfully flagged differences from manipulated specimen pairs as "error." The predicted performance of RPT-QC for analytical error detection (represented by smallest achievable allowable total error, given a probability of error detection ≥ 85% and a probability of false rejection ≤ 5%) for four common control rules is comparable to that of QCM-QC.

CONCLUSIONS

This study provides evidence that RPT-QC using canine heparinized plasma refrigerated for 7 days can be used with simple control rules and low numbers of control materials, suggesting RPT-QC is applicable to both reference and in-clinic laboratory settings.

Evaluation of several methodological challenges in circulating miRNA qPCR studies in patients with head and neck cancer

Circulating microRNAs (ci-miRNAs) in blood have emerged as promising diagnostic, prognostic and predictive biomarkers in cancer. Many clinical studies currently incorporate studies that assess ci-miRNAs. Validation of the clinical significance of candidate biomarker miRNAs has proven to be difficult, potentially resulting from vast discrepancies in the detection methodology as well as biological variability. In the current study, the influence of several methodological factors on ci-miRNA detection was evaluated as well as short-term biological variability in patients with head and neck cancer. RNA was isolated from 124 serum and plasma samples originating from patients with head and neck cancer and healthy volunteers. The miRNA levels were measured using RT-qPCR and the influence of pre-analytical factors, different normalization strategies and temporal reproducibility was assessed. RNA carriers improved ci-miRNA detection in serum and plasma specimens. A prolonged pre-processing time correlated with an increased hemolytic index in serum samples only. Hemolysis differentially affected the detection of individual miRNAs. Optimal normalization was achieved using the averaged detection values of spike-in cel-miR-39-3p and endogenous miR-16-5p. Comparing biological replicates from patients with head and neck cancer, the intra-individual miRNA levels were relatively stable (average interval 7 days). Differences in the ci-miRNA detection methodology and limitations of currently used technologies can greatly affect the results and may explain inconsistent outcomes between studies. Prior to the implementation of ci-miRNAs as useful clinical biomarkers, further advances in the standardization of the detection methodology and reduction of technical variability are needed.

Exogenous sample contamination. Sources and interference

Clinical laboratory medicine is involved in the vast majority of patient care pathways. It has been estimated that pathology results inform 60-70% of critical patient care decisions. The primary goal of the laboratory is to produce precise and accurate results which reflect the true situation in vivo. It is not surprising that interference occurs in laboratory analysis given the complexity of some of the assays used to perform them. Interference is defined as "the effect of a substance upon any step in the determination of the concentration or catalytic activity of the metabolite". Exogenous interferences are defined as those that derive from outside of the body and are therefore not normally found in a specimen and can cause either a positive or negative bias in analytical results. Interferences in analysis can come from various sources and can be classified as endogenous or exogenous. Exogenous substances could be introduced at any point in the sample journey. The laboratory must take responsibility for the quality of results produced. It has a responsibility to have processes in place to identify and minimise the occurrence and effect contamination and interference. To do this well the laboratory needs to work with clinicians and manufacturers. Failure to identify an erroneous result could have an impact on patient care, patient safety and also on hospital budgets. However it is not always easy to recognise interferences. This review summarises the types and sources of exogenous interference and some steps to minimise the impact they have.

Serum indices: managing assay interference

Clinical laboratories frequently encounter samples showing significant haemolysis, icterus or lipaemia. Technical advances, utilizing spectrophotometric measurements on automated chemistry analysers, allow rapid and accurate identification of such samples. However, accurate quantification of haemolysis, icterus and lipaemia interference is of limited value if laboratories do not set rational alert limits, based on sound interference testing experiments. Furthermore, in the context of increasing consolidation of laboratories and the formation of laboratory networks, there is an increasing requirement for harmonization of the handling of haemolysis, icterus and lipaemia-affected samples across different analytical platforms. Harmonization may be best achieved by considering both the analytical aspects of index measurement and the possible variations in the effects of haemolysis, icterus and lipaemia interferences on assays from different manufacturers. Initial verification studies, followed up with ongoing quality control testing, can help a laboratory ensure the accuracy of haemolysis, icterus and lipaemia index results, as well as assist in managing any biases in index results from analysers from different manufacturers. Similarities, and variations, in the effect of haemolysis, icterus and lipaemia interference in assays from different manufacturers can often be predicted from the mechanism of interference. Nevertheless, interference testing is required to confirm expected similarities or to quantify differences. It is important that laboratories are familiar with a number of interference testing protocols and the particular strengths and weaknesses of each. A rigorous approach to all aspects of haemolysis, icterus and lipaemia interference testing allows the analytical progress in index measurement to be translated into improved patient care.

Interference of medical contrast media on laboratory testing

The use of contrast media such as organic iodine molecules and gadolinium contrast agents is commonplace in diagnostic imaging. Although there is widespread perception that side effects and drug interactions may be the leading problems caused by these compounds, various degrees of interference with some laboratory tests have been clearly demonstrated. Overall, the described interference for iodinate contrast media include inappropriate gel barrier formation in blood tubes, the appearance of abnormal peaks in capillary zone electrophoresis of serum proteins, and a positive bias in assessment of cardiac troponin I with one immunoassay. The interference for gadolinium contrast agents include negative bias in calcium assessment with ortho-cresolphthalein colorimetric assays and occasional positive bias using some Arsenazo reagents, negative bias in measurement of angiotensin converting enzyme (ACE) and zinc (colorimetric assay), as well as positive bias in creatinine (Jaffe reaction), total iron binding capacity (TIBC, ferrozine method), magnesium (calmagite reagent) and selenium (mass spectrometry) measurement. Interference has also been reported in assessment of serum indices, pulse oximetry and methaemoglobin in samples of patients receiving Patent Blue V. Under several circumstances the interference was absent from manufacturer-supplied information and limited to certain type of reagents and/or analytes, so that local verification may be advisable to establish whether or not the test in use may be biased. Since the elimination half-life of these compounds is typically lower than 2 h, blood collection after this period may be a safer alternative in patients who have received contrast media for diagnostic purposes.

Lipemia: causes, interference mechanisms, detection and management

In the clinical laboratory setting, interferences can be a significant source of laboratory errors with potential to cause serious harm for the patient. After hemolysis, lipemia is the most frequent endogenous interference that can influence results of various laboratory methods by several mechanisms. The most common preanalytical cause of lipemic samples is inadequate time of blood sampling after the meal or parenteral administration of synthetic lipid emulsions. Although the best way of detecting the degree of lipemia is measuring lipemic index on analytical platforms, laboratory experts should be aware of its problems, like false positive results and lack of standardization between manufacturers. Unlike for other interferences, lipemia can be removed and measurement can be done in a clear sample. However, a protocol for removing lipids from the sample has to be chosen carefully, since it is dependent on the analytes that have to be determined. Investigation of lipemia interference is an obligation of manufacturers of laboratory reagents; however, several literature findings report lack of verification of the declared data. Moreover, the acceptance criteria currently used by the most manufacturers are not based on biological variation and need to be revised. Written procedures for detection of lipemia, removing lipemia interference and reporting results from lipemic samples should be available to laboratory staff in order to standardize the procedure, reduce errors and increase patient safety.