The evaluation and comparison of consecutive high speed centrifugation and LipoClear® reagent for lipemia removal

Comparison of lipemia interference created with native lipemic material and intravenous lipid emulsion in emergency laboratory tests

Introduction

This study aimed to investigate the effects of lipemia on clinical chemistry and coagulation parameters in native ultralipemic (NULM) and intravenous lipid emulsion (IVLE) spiked samples.

Materials and methods

The evaluation of biochemistry (photometric, ion-selective electrode, immunoturbidimetric method), cardiac (electrochemiluminescence immunoassay method) and coagulation (the viscosity-based mechanical method for prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen and the immunoturbidimetric method for D-dimer) parameters were conducted. In addition to the main pools, five pools were prepared for both types of lipemia, each with triglyceride (TG) concentrations of approximately 2.8, 5.7, 11.3, 17.0 and 22.6 mmol/L. All parameters' mean differences (MD%) were presented as interferographs and compared with the desirable specification for the inaccuracy (bias%). Data were also evaluated by repeated measures of ANOVA.

Results

Prothrombin time and APTT showed no clinically relevant interference in IVLE-added pools but were negatively affected in NULM pools(P < 0.001 in both parameters). For biochemistry, the most striking difference was seen for CRP; it is up to 134 MD% value with NULM (P < 0.001) at the highest TG concentration, whereas it was up to - 2.49 MD% value with IVLE (P = 0.009). Albumin was affected negatively upward of 5.7 mmol/L TG with IVLE, while there was no effect for NULM. Creatinine displayed significant positive interferences with NULM starting at the lowest TG concentration (P = 0.028). There was no clinically relevant interference in cardiac markers for both lipemia types.

Conclusions

Significant differences were scrutinized in interference patterns of lipemia types, emphasizing the need for careful consideration of lipemia interferences in clinical laboratories. It is crucial to note that lipid emulsions inadequately replicate lipemic samples.

High-speed centrifugation rather than Lipoclear reagent can be used for removing the interference of lipemia on serological tests of infectious diseases: AIDS, hepatitis B, hepatitis C, and syphilis by chemiluminescent microparticle immunoassay

The aim of this study was to investigate the interference of lipemia on measurement of HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, anti-HCV, HIV Ag/Ab, and anti-TP in serum by chemiluminescent microparticle immunoassay (CMIA) and compare lipemia removing performance between high-speed centrifugation and Lipoclear reagent. Mixed native serum samples (NSs) and hyperlipemia serum samples (HLS) were prepared for the investigated parameters. The levels of these parameters in NS and HLS were determined by CMIA on an Abbott ARCHITECT i2000SR immunoassay analyzer. HBsAg, anti-HBs, and anti-TP were affected with relative bias >12.5% (acceptable limit) when the level of triacylglycerol (TG) was higher than 27.12 mmol/L in HLS. Clinically unacceptable bias were observed for HBeAg and anti-HBe in HLS with TG higher than 40.52 mmol/L. However, anti-HCV and HIV Ag/Ab were not interfered in severe lipemia with TG < 52.03 mmol/L. In addition, the Lipoclear reagent did not reduce the interference of lipemia with relative bias from -62.50% to -18.02%. The high-speed centrifugation under the optimized condition of 12 000g for 10 min successfully removed the interference of lipemia with relative bias from -5.93% to 0% for HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, and anti-TP. To conclude, high-speed centrifugation can be used for removing the interference of lipemia to measure HBsAg, anti-HBs, HBeAg, anti-HBe, anti-HBc, and anti-TP. Accordingly, a standardized sample preanalytical preparation of the patients and other screening participants as well as a specimen examination procedure for removing lipemia interference on the serological tests was recommended.

Determination of lipemia acceptance thresholds for 31 immunoassay analytes

BACKGROUND

Lipemia is one of common endogenous interferences that can compromises sample quality and potentially influence results of various laboratory methods. Determination of the lipemic index or triglyceride concentrations are used to define the degree of lipemia. This study was aimed to establish lipemic index (LI) and triglyceride thresholds above where significant interference exists for 31 immunoassay analytes measured on Roche Cobas 6000.

MATERIALS AND METHODS

The study was carried out following CLSI C56-A and EP07-ED3:2018 guidelines using sample pools spiked with increasing concentrations of lipid emulsion solution, reaching 70 mmol/L. To define the LI and triglyceride thresholds, the bias from concentration in the native sample was calculated at different lipemia degree and compared with allowable error limits based on biological variation or state-of-the-art technology.

RESULTS

No lipemia interference was observed for 27 out of 31 analytes even at the highest concentrations of lipid emulsion (LI ranging from 1737 to 2086 mg/dL, triglyceride concentration 60.34-73.99 mmol/L). However, progesterone, 25-OH vitamin D, testosterone, and estradiol were negatively affected by lipemia at 217 mg/dL (9.58 mmol/L), 222 mg/dL (10.66 mmol/L), 478 mg/dL (18.81 mmol/L), and 941 mg/dL (35.82 mmol/L) of the LI (triglyceride concentration), respectively.

CONCLUSION

Most immunoassays evaluated in this study were found to be robust to lipemia interference. By using these thresholds, laboratories can report the immunoassay results from analyzing a lipemic patient sample in many cases.

Handling of lipemic samples in the clinical laboratory

Interferences in the clinical laboratory may lead physicians misinterpret results for some biological analytes. The most common analytical interferences in the clinical laboratory include hemolysis, icterus and lipemia. Lipemia is defined as turbidity in a sample caused by the accumulation of lipoproteins, mainly very-low density lipoproteins (VLDL) and chylomicrons. Several methods are available for the detection of lipemic samples, including the lipemic index, or triglyceride quantification in serum or plasma samples, or mean corpuscular hemoglobin (MCHC) concentration in blood samples. According to the European Directive 98/79/CE, it is the responsibility of clinical laboratories to monitor the presence of interfering substances that may affect the measurement of an analyte. There is an urgent need to standardize interference studies and the way interferences are reported by manufacturers. Several methods are currently available to remove interference from lipemia and enable accurate measurement of biological quantities. The clinical laboratory should establish a protocol for the handling of lipemic samples according to the biological quantity to be tested.

Elimination of lipaemic interference by high-speed centrifugation

Introduction

In order to deliver high quality results, detection and elimination of possible analytical interferences, such as lipaemia, is crucial. The aim of this study is to evaluate the efficacy of high-speed centrifugation in eliminating lipaemic interference and to define own lipaemic index (LI) for the studied biochemical analytes.

Materials and methods

Evaluated analytes were: albumin, alkaline phosphatase, alanine-aminotransferase (ALT), aspartate-aminotransferase (AST), calcium, creatinine, gamma-glutamyltransferase (GGT), glucose, phosphates, total proteins, urea and total bilirubin. Those analytes and LIs have been analysed in duplicate in the Roche Diagnostics-c8000 analyser in samples centrifuged at 3000 rpm/10 minutes in the SL16 (Thermo Scientific, Waltham, USA) centrifuge and according to an own high-speed centrifugation protocol (12,900 rpm/15 minutes) in the MicroCL17R (Thermo Scientific, Waltham, USA) centrifuge. Lipaemia has been measured in each sample. The efficiency of high-speed centrifugation is verified by the Wilcoxon test (P < 0.05). In cases where significant differences are observed, our own LI is calculated. For ALT and AST, it is verified by McNemar test (P < 0.05). For creatinine, both Wilcoxon and McNemar test were applied.

Results

There were statistically significant differences in analyte concentration before and after high-speed centrifugation for: albumin, creatinine, GGT, glucose, phosphates, urea and total bilirrubin. Own LI is calculated. McNemar test shows statistically significant diferences in the proportion of delivered results before and after high-speed centrifugation in ALT, AST and creatinine.

Conclusions

This study confirms the efficacy of high-speed centrifugation protocol for all the considered analytes, excepting calcium, alkaline phosphatase and total proteins.

Ultracentrifugation for Coagulation Testing

Lipemia is known to potentially affect coagulation testing. It may be detected with newer coagulation analyzers that are validated to assess hemolysis, icterus, and lipemia (HIL) in a plasma sample. In samples with lipemia where accuracy of the test result is compromised, strategies for mitigating the lipemia interferences would be required. The tests affected by lipemia are those using chronometric, chromogenic, immunologic, or other light scattering/reading principles. Ultracentrifugation is one process that has been effectively demonstrated to remove lipemia from blood samples to allow for more accurate measurements. In this chapter, a description of one ultracentrifugation method is provided.

Effects of lipemia on capillary serum protein electrophoresis in native ultra-lipemic material and intravenous lipid emulsion added sera

OBJECTIVES

This study aims to investigate the effect of natural ultralipemic material (NULM) and intravenous lipid emulsion (IVLE) on capillary serum protein electrophoresis (SPEP).

METHODS

NULM material was prepared from leftover patients' lipemic serum sample (triglyceride concentration >2,000 mg/dL) pool by a refrigerated high-speed centrifuge, and IVLE Omegaven lipid emulsion (30%) was used. Serum pools for interference study were prepared from patient samples for which serum protein electrophoresis was studied as Normal SPEP and M Peak SPEP. For both types of lipemia (DULM and IVLE), five pools with triglyceride concentrations of ∼4.52 mmol/L, ∼7.91 mmol/L, ∼14.69 mmol/L, ∼21.47 mmol/L, and ∼28.25 mmol/L were prepared. SPEP was studied in each pool with Sebia Capillarys Minicap. A repeated measure ANOVA test was used to determine the difference between the pools, and interferograms were used to evaluate the interference effect.

RESULTS

Interference was not detected in IVLE added Normal SPEP and M Peak SPEP pools, either % or concentrations of fractions. In NULM-added Normal SPEP and M Peak SPEP pools, significant positive interference in albumin % (p=0.002 and p<0.001 respectively) and significant negative interference in gamma% (p<0.001 and p=0.005 respectively) and M protein peak (p=0.002) fractions were detected. However, significant positive interference was seen only for albumin concentration fractions (p<0.001 for both pools).

CONCLUSIONS

It is vital to use NULM instead of IVLE solutions in lipemia interference studies for all laboratory tests, including CZE SPEP. The fractions concentration values calculated with the total protein concentration should be used for evaluating SPEP results.

Investigating the effects of endogenous lipaemia on the measurement of sodium by indirect ion specific electrode potentiometry

BACKGROUND

The widely automated method using indirect ion specific electrodes (ISE) potentiometry for determination of sodium concentration is prone to interference from lipaemia. Manufacturer-specified lipaemic (L)-index cut offs may underestimate the effects of endogenous lipaemia.

METHODS

We assessed the interference on sodium concentration caused by endogenous lipaemia in 32 residual samples (from 13 patients) using indirect ISE (Cobas^® 8000 modular analyser with c702 module, Roche diagnostics) and direct ISE (GEM 4000 premier, Werfen) potentiometric methods. Regression analysis (linear and non-linear) was used to determine a reliable (L)-index cut off for reporting sodium concentration.

RESULTS

There was a poor correlation observed between triglyceride concentration and (L)-index. There was significant negative interference caused by endogenous lipaemia within analysed samples. Non-linear regression demonstrated a negative interference of approximately 5% at an (L)-index of 250.

CONCLUSION

At present, the manufacturer advises not to report sodium concentration by indirect ISE on the Cobas^® 8000 modular analyser if the (L)-index is >2000. However, this has been determined by the addition of exogenous lipids (Intralipid^®) and it is clear that this is not comparable to endogenous lipaemia. To ensure patient safety, clinical laboratories should consider lowering the cut off for (L)-index that they use for reporting sodium concentration.

Methods to reduce lipemic interference in clinical chemistry tests: a systematic review and recommendations

OBJECTIVES

Lipemia is the presence of abnormally high lipoprotein concentrations in serum or plasma samples that can interfere with laboratory testing. There is little guidance available from manufacturers or professional bodies on processing lipemic samples to produce clinically acceptable results. This systematic review summarizes existing literature on the effectiveness of lipid removal techniques in reducing interference in clinical chemistry tests.

METHODS

A PubMed search using terms relating to lipid removal from human samples for clinical chemistry tests produced 1,558 studies published between January 2010 and July 2021. 15 articles met the criteria for further analyses.

RESULTS

A total of 66 analytes were investigated amongst the 15 studies, which showed highly heterogenous study designs. High-speed centrifugation was consistently effective for 13 analytes: albumin, alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, creatine kinase (CK), creatinine (Jaffe method), gamma-glutamyl transferase (GGT), glucose (hexokinase-based method), lactate dehydrogenase (LDH), phosphate, potassium, and urea. Lipid-clearing agents were uniformly effective for seven analytes: ALT, AST, total bilirubin, CK, creatinine (Jaffe method), lipase, and urea. Mixed results were reported for the remaining analytes.

CONCLUSIONS

For some analytes, high-speed centrifugation and/or lipid-clearing agents can be used in place of ultracentrifugation. Harmonized protocols and acceptability criteria are required to allow pooled data analysis and interpretation of different lipemic interference studies.

Improving the laboratory result release process in the light of ISO 15189:2012 standard

The ISO 15189:2012 standard section 5.9.1 requires laboratories to review results before release, considering quality control, previous results, and clinical information, if any, and to issue documented procedures about it. While laboratory result reporting is generally regarded as part of the post-analytical phase, the result release process requires a general view of the total examination process. Reviewing test results may follow with troubleshooting and test repetition, including reanalyzing an individual sample or resampling. A systematic understanding of the result release may help laboratory professionals carry out appropriate test repetition and ensure the plausibility of laboratory results. In this paper, we addressed the crucial steps in the result release process, including evaluation of sample quality, critical result notification, result reporting, and recommendations for the management of the result release, considering quality control alerts, instrument flags, warning messages, and interference indexes. Error detection tools and plausibility checks mentioned in the present paper can support the daily practice of results release.

Pretreatment of Body Fluid Specimens Using Hyaluronidase and Ultracentrifugation

OBJECTIVE

Viscous body fluids present challenges during clinical laboratory testing. The present study was conducted to evaluate the effectiveness of hyaluronidase (HYAL) and ultracentrifugation (UC) pretreatment for a variety of body fluids before clinical chemistry testing.

METHODS

The following body fluids were evaluated: biliary/hepatic, cerebrospinal, dialysate, drain, pancreatic, pericardial, peritoneal/ascites, pleural, synovial, and vitreous. Analytes assessed included amylase, total bilirubin, cancer antigen 19-9, carcinoembryonic antigen, cholesterol, chloride, creatinine, glucose, lactate dehydrogenase, lipase, potassium, rheumatoid factor, sodium, total protein, triglycerides, urea nitrogen, and uric acid.

RESULTS

Observed percentage differences between HYAL treated and untreated fluids were less than ±15% for all analytes investigated, with a small number showing statistical significance (P <.05). In addition, UC showed increased variability for limited body fluid/analyte combinations.

CONCLUSION

The HYAL treatment effectively reduced viscosity for body fluids. Validation of specimen pretreatment processes ensures acceptable analytical performance and the absence of unanticipated interferences.

Does the use of fish oil-based lipid emulsion in the clinical setting of total parenteral nutrition and lipid rescue therapy interfere with common laboratory analytes on Roche Cobas 6000?

BACKGROUND

Lipaemic interference on automated analysers has been widely studied using soy-based emulsion such as Intralipid. Due to the greater adoption of fish oil-based lipid emulsion for total parenteral nutrition in view of improved clinical outcomes, we seek to characterize the optical properties of SMOFlipid 20% (Fresenius Kabi, Bad Homburg, Germany), a fish oil-based emulsion, on the Roche Cobas 6000 chemistry analyser (Roche Diagnostic, Basel, Switzerland).

METHOD

Various amounts of SMOFlipid were spiked into pooled serums. We plotted Roche Cobas Serum Index Gen.2 Lipaemia Index (L-index) against the amount of SMOFlipid added. We then studied the interference thresholds for aspartate aminotransferase, alanine aminotransferase, albumin and renal panel analytes using SMOFlipid. We subjected five levels of spiked lipaemia to high-speed centrifugation and analysed the specimens pre- and post-centrifugation. To postulate whether fish oil-based lipid emulsion interferes with laboratory results in the clinical setting, we calculated concentrations of SMOFlipid post-lipid rescue therapy and steady-state concentration of a typical total parenteral nutrition regime using pharmacokinetic principles.

RESULTS

SMOFlipid optical behaviour is similar to Intralipid using the Serum Index Gen.2 L-index, with 1 mg/dL of SMOFlipid representing 1 unit of L-index. Manufacturer-stated interference thresholds are accurate for alanine aminotransferase, aspartate aminotransferase, albumin, urea and creatinine. High-speed centrifugation at 60 min 21,100g facilitates the removal of fish oil-based SMOFlipid.

CONCLUSION

Based on the interference thresholds we verified and pharmacokinetics parameters provided by SMOFlipid manufacturer, total parenteral nutrition may not interfere with chemistry analytes given sufficient clearance, but lipid rescue therapy will interfere. Further studies assessing lipaemic interference on immunoassays are needed.

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.

The Estimation of Postmortem Serum Urea via the Ultrafiltration of Hemolyzed Blood

Postmortem serum urea has been demonstrated as an objective indicator for the forensic diagnosis of cause of death. However, samples used in postmortem biochemical analysis are always affected by hemolysis. To investigate whether hemolysis affects the biochemical analysis of urea and to explore the feasibility of using ultrafiltration to process hemolyzed blood samples, three different levels of hemolyzed blood samples were used to assess the influence of hemolysis on postmortem biochemical analysis of urea, and two ultrafiltration methods were used to process the hemolyzed blood samples. Bias% was used to assess the interference of hemolysis. Our results showed that heavy hemolysis had a significant influence on the biochemical analysis of urea. Both ultrafiltration methods in the present study could significantly reduce the interference of hemolysis, with the |bias%| of methods A and B decreasing from 69.74% ± 99.14% to 12.18% ± 7.23% and 10.77% ± 8.09%, respectively, compared to the original serum. After regression correction, there was no significant difference between the urea concentration in the ultrafiltrates of the two ultrafiltration methods and that in the original serum, which suggested that the postmortem serum urea concentration could be estimated by the corrected urea concentration in the ultrafiltrate. The current study also provided possible pretreatment methods for postmortem biochemical analysis of other biomarkers in hemolyzed blood samples of forensic practice.

Comparative analysis of high CRP-levels in human blood using point-of-care and laboratory-based methods

Objectives

The use of point-of-care (POC) methods and the measurements of C-reactive protein (CRP) as a diagnostic marker have both increased over the past years. This has led to an increase in POC-methods analysing CRP. High CRP levels are often seen as an indication for the subscription of antibiotics. The quality of POC-systems compared to routine diagnostic measurements for the analysis of CRP is thereby of main importance, since many small practises will use POC-methods. This study compared high-level CRP concentrations (above 100 mg/L) using an i-CHROMA^TM with 2 routinely used laboratory-based systems (Architect and ABX).

Design

and Methods: A total of 199 patient samples with a CRP concentration above 100 mg/L were analysed with the i-CHROMA^TM POC system and the turbidimetric routine methods using the Architect and ABX equipment.

Results

The results of the i-CHROMA^TM device showed a significant decrease in the CRP levels compared to those obtained with the Architect and the ABX (i-CHROMA^TM vs. Architect: y ​= ​0.6792x + 94.701; R² = 0.4980, i-CHROMA^TM vs. ABX: y ​= ​0.3674x + 118.05; R² ​= ​0.3964, Architect vs. ABX: y ​= ​0.7657x + 36.337; R² = 0.9311). Furthermore, data analysis showed a partition of the i-CHROMA^TM measurements in two defined clouds, which could not be explained with any of the available sample information.

Conclusions

This analysis showed the limitations of the i-CHROMA^TM CRP analyser. In addition, it illustrates the need for strict regulations on the information and output provided by companies regarding the boundaries of novel and existing diagnostic methods.

Effects of marked hypertriglyceridemia and lipid clearance techniques on canine biochemistry testing

Triglyceride concentrations in dogs with hyperlipidemic disorders can exceed concentrations used by assay manufacturers for interference testing. High-speed centrifugation or the polar solvent LipoClear reduce triglyceride concentrations, but efficacy requires evaluation in veterinary species. We determined the effect of marked hypertriglyceridemia on canine biochemistry testing; assessed the ability of high-speed centrifugation or LipoClear to correct lipemic interferences; and determined if LipoClear introduces inaccuracy into biochemistry assays. Fifteen pooled canine serum samples were aliquoted and spiked with equal volumes of water or Intralipid [triglyceride concentration 33.9 mmol/L (3,000 mg/dL)]. Intralipid aliquots underwent lipid removal by high-speed centrifugation or LipoClear treatment, and a water-spiked aliquot underwent LipoClear treatment. Biochemistry panels were performed using a Vitros 4600 chemistry analyzer. Results were compared by paired t-test or Wilcoxon test. Total observed errors were considered clinically acceptable if below veterinary allowable total error (TEa) guidelines. Statistically significant (p ≤ 0.05) interferences were introduced by Intralipid for 15 of 15 analytes. Median observed error exceeded TEa for potassium and enzymatic carbon dioxide, neither of which were identified by the manufacturer as susceptible to lipemic interference. After centrifugation, median observed error exceeded TEa for potassium and chloride. LipoClear treatment resulted in median errors that exceeded TEa for total protein, chloride, and phosphorus. Given that severe lipemia can occur in dogs with primary or secondary hyperlipidemia, veterinary laboratories should perform their own interference testing at triglyceride concentrations relevant to their patient population and provide this information to clinicians to ensure optimal case management.

Removing Lipemia in Serum/Plasma Samples: A Multicenter Study

BACKGROUND

Lipemia, a significant source of analytical errors in clinical laboratory settings, should be removed prior to measuring biochemical parameters. We investigated whether lipemia in serum/plasma samples can be removed using a method that is easier and more practicable than ultracentrifugation, the current reference method.

METHODS

Seven hospital laboratories in Spain participated in this study. We first compared the effectiveness of ultracentrifugation (108,200×g) and high-speed centrifugation (10,000×g for 15 minutes) in removing lipemia. Second, we compared high-speed centrifugation with two liquid-liquid extraction methods-LipoClear (StatSpin, Norwood, USA), and 1,1,2-trichlorotrifluoroethane (Merck, Darmstadt, Germany). We assessed 14 biochemical parameters: serum/plasma concentrations of sodium ion, potassium ion, chloride ion, glucose, total protein, albumin, creatinine, urea, alkaline phosphatase, gamma-glutamyl transferase, alanine aminotransferase, aspartate-aminotransferase, calcium, and bilirubin. We analyzed whether the differences between lipemia removal methods exceeded the limit for clinically significant interference (LCSI).

RESULTS

When ultracentrifugation and high-speed centrifugation were compared, no parameter had a difference that exceeded the LCSI. When high-speed centrifugation was compared with the two liquid-liquid extraction methods, we found differences exceeding the LCSI in protein, calcium, and aspartate aminotransferase in the comparison with 1,1,2-trichlorotrifluoroethane, and in protein, albumin, and calcium in the comparison with LipoClear. Differences in other parameters did not exceed the LCSI.

CONCLUSIONS

High-speed centrifugation (10,000×g for 15 minutes) can be used instead of ultracentrifugation to remove lipemia in serum/plasma samples. LipoClear and 1,1,2-trichlorotrifluoroethane are unsuitable as they interfere with the measurement of certain parameters.

Variability and Error in Cardiac Troponin Testing: An ACLPS Critical Review

OBJECTIVES

To provide a comprehensive overview of the complexities associated with cardiac troponin (cTn) testing. An emphasis is placed on the sources of error, organized into the preanalytical, analytical, and postanalytical phases of the testing pathway. Controversial areas are also explored.

METHODS

A case scenario and review of the relevant literature describing laboratory considerations involving cTn testing are described.

RESULTS

Advanced comprehension of the specific assay used in a given laboratory is necessary for optimal reporting, utilization, and quality monitoring of cTn.

CONCLUSIONS

cTn assays are reliable diagnostic tests for acute myocardial infarction, but understanding their limitations is required for appropriate result interpretation.

Immunoassay quantification of human insulin added to ternary parenteral nutrition containers: comparison of two methods

Adding insulin directly into infusion bags seems to be a useful method for controlling hyperglycemia in patients under ternary parenteral nutrition (TPN). Its efficacy is assessed by glycemic monitoring but few data are available on insulin stability in this situation. Among the various methods for quantifying insulin levels in human serum, the immunoassay ones seemed potentially appropriate for a TPN admixture containing high lipid concentrations. We sought to identify and validate which of two immunoassay methods was the better to quantify human insulin and consequently be adapted to studying its stability in a TPN admixture. Two immunoassay methods to quantify recombinant human insulin were assessed in industrial TPN: an immunoradiometric assay (IRMA) and an immunoelectrochemiluminometric assay (IECMA). Validation trials for both methods were based on the accuracy profile method. Interference with immunometric assays due to the high lipidic content of TPN was eliminated through an improved preparation protocol using a bovine serum albumin (BSA) diluted in phosphate buffer saline (PBS). The relative total error of IECMA varied from 1.74 to 4.52% while it varied from -0.32 to 8.37% with IRMA. Only IECMA provided an accuracy profile with a 95% confidence interval of calculated-tolerance limits falling between the chosen acceptance limits (i.e., total error ≤±10%). IECMA combined with a BSA dilution is a simple and semi-automatic method that provides an accurate quantification of human insulin in a TPN admixture without any interference from lipids.

Preanalytical external quality assessment of the Croatian Society of Medical Biochemistry and Laboratory Medicine and CROQALM: finding undetected weak spots

INTRODUCTION

The aim of this paper is to present results of first two years of preanalytical external quality assessment (EQA) in Croatia.

MATERIALS AND METHODS

This paper summarizes results from 6 rounds of preanalytical EQA during 2014-2016 in 161-175 Croatian laboratories (number ranged between cycles). EQA was designed as an online survey of the compliance with National recommendations for phlebotomy (NRP). Forty-seven questions in 5 categories are analyzed (materials and equipment, patient identification, patient preparation, sampling and storage). Additionally, preanalytical cases are presented. Overall performance scores (Question score (Qscore) for compliance with NRP and Case score (Cscore) for preanalytical cases) are calculated for each question/case as a proportion of laboratories with satisfactory procedure (x 100). Qscores and Cscores ≥ 70 were classified as acceptable (maximal score = 100).

RESULTS

In investigation of compliance with NRP, acceptable Qscores were obtained for 34/47 questions. The lowest scores were observed for the availability of sterile disposable tourniquets (Qscore = 15) and safe-sharp needles (Qscore = 34), obtaining patients address as an identifier (Qscore = 21), using glycolysis inhibitor tubes for glucose concentration measurement (Qscore = 21) and verification of manufacturers declarations on temperature and time of storage (Qscore = 31). There was no statistically significant difference in overall Qscore according to different categories of phlebotomy procedures (P = 0.284). The results of preanalytical cases showed acceptable Cscore values for all cases (89-96).

CONCLUSION

First two years of preanalytical EQA showed good compliance with the NRP and excellent expertise in resolving complex preanalytical issues. Major critical spots are lack of availability of safe-sharp needles, disposable tourniquets and glucose inhibitor tubes.

Frequency and causes of lipemia interference of clinical chemistry laboratory tests

Objectives

The aims of this study were to identify the causes of severe lipemia in an academic medical center patient population and to determine the relationship between lipemia and hemolysis.

Design and methods

Retrospective study was done on the data from the core clinical laboratory at an academic medical center. Lipemic indices were available for all chemistry specimens analyzed over a 16-month period (n=552,029 specimens) and for serum/plasma triglycerides concentrations ordered for clinical purposes over a 16-year period (n=393,085 specimens). Analysis was performed on Roche Diagnostics cobas 8000 analyzers. Extensive chart review was done for all specimens with lipemic index greater than 500 (severely lipemic) and for all specimens with serum/plasma triglycerides greater than 2000 mg/dL. We also determined the relationship between lipemia and hemolysis.

Results

The most frequent suspected causes of very high lipemic index (>500) were found to be lipid-containing intravenous infusions (54.4% of total; fat emulsions for parenteral nutrition – 47%; propofol −7.4%) and diabetes mellitus (25% of total, mainly type 2). The most frequent suspected causes of very elevated serum/plasma triglycerides (>2000 mg/dL) was diabetes mellitus (64%, mainly type 2) and hyperlipidemia (16.9%). The frequency of hemolysis increased with increasing lipemic index.

Conclusions

Intravenous lipid infusions and type 2 diabetes were the most common causes of severe lipemia in this study at an academic medical center. Given that iatrogenic factors are the most common cause of severe lipemia, education and intervention may be helpful in reducing frequency of severe lipemia in patient specimens.

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Intravenous lipids and type 2 diabetes were most common causes of severe lipemia.

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The frequency of hemolysis increased with increasing lipemic index.

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Diabetes type 2 was the most common cause of extreme hypertriglyceridemia.

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Education and intervention may be helpful in reducing frequency of lipemia.

Pre-analytic variability in cardiovascular biomarker testing

The impact of laboratory medicine on clinical cardiology has dramatically increased over the years and a lot of cardiovascular biomarkers have been recently proposed. In order to avoid clinical mistakes, physicians should be well aware of all the aspects, which could affect the quality of laboratory results, remembering that pre-analytic variability is an often overlooked significant source of bias, determining the vast majority of laboratory errors. This review addresses the determinants of pre-analitycal variability in cardiovascular biomarker testing, focusing on the most widespread biomarkers, which are cardiac troponins and natriuretic peptides.

Laboratory Diagnostics and Quality of Blood Collection

Diagnostic blood samples collected by phlebotomy are the most common type of biological specimens drawn and sent to laboratory medicine facilities for being analyzed, thus supporting caring physicians in patient diagnosis, follow-up and/or therapeutic monitoring. Phlebotomy, a relatively invasive medical procedure, is indeed critical for the downstream procedures accomplished either in the analytical phase made in the laboratory or in the interpretive process done by the physicians. Diagnosis, management, treatment of patients and ultimately patient safety itself can be compromised by poor phlebotomy quality. We have read with interest a recent article where the authors addressed important aspects of venous blood collection for laboratory medicine analysis. The authors conducted a phlebotomy survey based on the Clinical and Laboratory Standard Institute (CLSI) H03-A6 document (presently replaced by the GP41-A6 document) in three government hospitals in Ethiopia to evaluate 120 professionals (101 non-laboratory professionals vs. 19 laboratory professionals) as regards the venous blood collection practice. The aim of this mini (non-systematic) review is to both take a cue from the above article and from current practices we had already observed in other laboratory settings, and discuss four questionable activities performed by health care professionals during venous blood collection. We refer to: i) diet restriction assessment; ii) puncture site cleansing; iii) timing of tourniquet removal and; iv) mixing specimen with additives.

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.