Liquid citrate acidification introduces significant glucose bias and leads to misclassification of patients with diabetes

Glucose measurements are crucial in diabetes diagnosis. We aimed to assess the effectiveness of liquid citrate acidification in preventing glycolysis and investigate glucose stability in serum, sodium fluoride (NaF/KOx) and Glucomedics tubes.

Samples from 40 participants were collected in serum, lithium-heparin (LiH), sodium fluoride/potassium oxalate (NaF/KOx) and Glucomedics tubes. Glucose was measured within 60 min (baseline), 120 and 180 min from venipuncture. Serum, NaF/KOx and Glucomedics values at baseline were compared to LiH glucose concentration. Additionally, glucose values measured at 120 and 180 min from each tube were compared with the baseline value. Mean absolute bias for each tube and time point was calculated and compared to recommended criteria. The regression equation obtained comparing citrate to NaF/KOx tubes was used to recalculate glucose results retrieved from the laboratory information system.

Glucose measured in Glucomedics was higher (9.9%; p<0.001), while glucose in NaF/KOx and serum was lower compared to LiH (2.4%; p<0.001 and 3.2%; p<0.001, respectively). Biases for all tubes were clinically significant. Glucose remained unchanged at room temperature in all tubes for up to 180 min after venipuncture. Observed bias caused by Glucomedics leads to a 10.6% increase in diabetes prevalence (p<0.001).

Inhibition of glycolysis is most effectively achieved using liquid citrate acidification, compared to LiH, NaF/KOx or serum. Due to clinically significant bias relative to reference glucose, the interchangeable use of different tube types for serial glucose measurements is not recommended. The replacement of NaF/KOx with Glucomedics tubes substantially impacts glucose results, giving marked rise in diabetes prevalence.

The role of human kallikrein 6, clusterin and adiponectin as potential blood biomarkers of dementia

OBJECTIVES

Progressive degenerative syndromes which affect brain, altering memory, behavior, cognition and emotion, are commonly defined as dementia. It was suggested that serum human kallikrein 6 (KLK6), clusterin (CLU) and adiponectin (ADPN) in combination with inflammation markers, neuroimaging and neuropsychological testing could assist in discriminating dementia patients from control individuals. Our aim was therefore to compare serum concentrations of KLK6, CLU and ADPN and inflammatory marker, interleukin-6 (IL-6), in patients suffering from Alzheimer's disease (AD), patients with vascular dementia (VAD), cognitively healthy participants (CHP) and those with mild cognitive impairment (MCI).

DESIGN AND METHODS

Serum samples were collected from AD, VAD and MCI patients admitted to the University Department of Neurology (Zagreb, Croatia) for regular follow-up. All patients underwent standard neuroimaging procedures including brain CT, neurosonological assessment with intima-media thickness (IMT) and breath holding index (BHI) calculations. Cognitive abilities were tested using standard Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). Concentrations of KLK6, CLU, ADPN and IL-6 were determined in all serum samples.

RESULTS

We have recruited a total of 235 participants, divided in 4 groups: AD (N=70), VAD (N=67), MCI (N=48) and CHP (N=50). Serum concentrations of KLK6 (P=0.137), CLU (P=0.178) and ADPN (P=0.268) did not differ between AD, VAD, MCI and cognitively healthy control group of participants, whereas IL-6 was significantly higher in VAD patients than in AD, MCI and CHP individuals (P=0.014). There was no association between investigated biomarkers and clinical patient parameters.

CONCLUSIONS

Serum concentrations of KLK6, CLU and ADPN do not differ between AD, VAD and controls with and without mild cognitive impairment. Higher IL-6 levels in VAD group point to the inflammatory component in the development of vascular dementia. Investigated biomarkers are not associated with neuroimaging findings and neuropsychological patient data.

Biochemia Medica's editorial policy on authorship

Recent findings of authorship criteria violations in the manuscripts submitted to Biochemia Medica show that almost 40% of authors do not meet necessary criteria for authorship and thus indicate the need for better dissemination of editorial policy on authorship in our journal. We believe that such cases are mostly due to the authors' unawareness or the lack of understanding of the authorship criteria. With this article we therefore wish to declare our editorial policy on authorship and authorship criteria. Biochemia Medica endorses the authorship policy provided by the International Committee of Medical Journal Editors (ICMJE). Information on authorship is assessed by self-reported authorship claims during on-line manuscript submission. Those who meet ICMJE criteria shall be listed as authors, and all listed authors shall fulfill ICMJE criteria. All authors should be responsible for content of the article and have to know other authors' contributions to the study. Biochemia Medica will follow recommendations provided by Committee on Publication Ethics (COPE) flowcharts for possible disputes. By adhering to this procedure we hope to raise awareness about the importance of compliance with ICMJE authorship recommendations.

The quality and scope of information provided by medical laboratories to patients before laboratory testing: Survey of the Working Group for Patient Preparation of the Croatian Society of Medical Biochemistry and Laboratory Medicine

INTRODUCTION

The aim of this work was to evaluate to what extent the scope and content of information provided to patients is standardized across medical biochemistry laboratories in Croatia.

MATERIALS AND METHODS

Two on-line self-report surveys were sent out: Survey A regarding attitudes on importance of patient preparation and Survey B on the contents of patient preparation instructions.

RESULTS

13/118 laboratories (11%) do not provide written instructions to patients on how to prepare for laboratory testing, and 36 (40%) do not include information about water intake in their instructions. Only half of laboratories provide instructions for prostate-specific antigen (53.8%), female sex hormones (53.7%) and therapeutic drug monitoring (TDM) (52.5%). Inadequate information about fasting status (55.0%) and 24 hour urine collection (77.9%) were frequent errors with high severity and were associated with the greatest potential to cause patient harm.

CONCLUSIONS

Laboratory professionals in Croatia have a positive attitude towards the importance of patient preparation for laboratory testing. However, the information for laboratory testing is not standardized and frequently lacks guidance for tests related to TDM, coagulation and endocrinology. This study highlights the need for standardized, updated and evidence-based recommendations for patient preparation in order to minimize the risk for patients.

Short-term and long-term storage stability of heparin plasma ammonia

Aims

Ammonia is an extremely unstable analyte and requires special attention during sampling, transport and storage. The aim of this study was to evaluate the stability of ammonia in lithium-heparin plasma during short-term (at +4°C) and long-term (at −20°C) storage.

Methods

Twenty plasma samples were used for short-term stability assessment. Each sample was divided into five aliquots and stored in stoppered tubes at +4°C, for 1, 2, 3, 4 and 24 h from initial testing. Fifteen plasma samples were used for long-term stability assessment. Each sample was divided into eight aliquots and stored in stoppered tubes at −20°C for 3, 24, 48 h and 1, 2, 4, 8 and 12 weeks from initial testing. Ammonia concentration was determined on a Beckman Coulter AU2700 chemistry analyser using Randox ammonia enzymatic UV method. Bias was calculated from initial value for each time point and compared with quality specifications defined by Royal College of Pathologists of Australasia.

Results

The average bias exceeded the total allowable error after storage of samples for 1 h at +4°C and 3 h at −20°C.

Conclusion

Ammonia is not stable during storage at +4°C and −20°C in lithium-heparinised plasma and should therefore be analysed immediately.

How to assess the quality of your analytical method?

Laboratory medicine is amongst the fastest growing fields in medicine, crucial in diagnosis, support of prevention and in the monitoring of disease for individual patients and for the evaluation of treatment for populations of patients. Therefore, high quality and safety in laboratory testing has a prominent role in high-quality healthcare. Applied knowledge and competencies of professionals in laboratory medicine increases the clinical value of laboratory results by decreasing laboratory errors, increasing appropriate utilization of tests, and increasing cost effectiveness. This collective paper provides insights into how to validate the laboratory assays and assess the quality of methods. It is a synopsis of the lectures at the 15th European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Continuing Postgraduate Course in Clinical Chemistry and Laboratory Medicine entitled “How to assess the quality of your method?” (Zagreb, Croatia, 24–25 October 2015). The leading topics to be discussed include who, what and when to do in validation/verification of methods, verification of imprecision and bias, verification of reference intervals, verification of qualitative test procedures, verification of blood collection systems, comparability of results among methods and analytical systems, limit of detection, limit of quantification and limit of decision, how to assess the measurement uncertainty, the optimal use of Internal Quality Control and External Quality Assessment data, Six Sigma metrics, performance specifications, as well as biological variation. This article, which continues the annual tradition of collective papers from the EFLM continuing postgraduate courses in clinical chemistry and laboratory medicine, aims to provide further contributions by discussing the quality of laboratory methods and measurements and, at the same time, to offer continuing professional development to the attendees.

Biochemia Medica’s editorial policy on authorship

Recent findings of authorship criteria violations in the manuscripts submitted to Biochemia Medica show that almost 40% of authors do not meet necessary criteria for authorship and thus indicate the need for better dissemination of editorial policy on authorship in our journal. We believe that such cases are mostly due to the authors’ unawareness or the lack of understanding of the authorship criteria. With this article we therefore wish to declare our editorial policy on authorship and authorship criteria. Biochemia Medica endorses the authorship policy provided by the International Committee of Medical Journal Editors (ICMJE). Information on authorship is assessed by self-reported authorship claims during on-line manuscript submission. Those who meet ICMJE criteria shall be listed as authors, and all listed authors shall fulfill ICMJE criteria. All authors should be responsible for content of the article and have to know other authors’ contributions to the study. Biochemia Medica will follow recommendations provided by Committee on Publication Ethics (COPE) flowcharts for possible disputes. By adhering to this procedure we hope to raise awareness about the importance of compliance with ICMJE authorship recommendations.

Preanalytical quality improvement: in quality we trust

Total quality in laboratory medicine should be defined as the guarantee that each activity throughout the total testing process is correctly performed, providing valuable medical decision-making and effective patient care. In the past decades, a 10-fold reduction in the analytical error rate has been achieved thanks to improvements in both reliability and standardization of analytical techniques, reagents, and instrumentation. Notable advances in information technology, quality control and quality assurance methods have also assured a valuable contribution for reducing diagnostic errors. Nevertheless, several lines of evidence still suggest that most errors in laboratory diagnostics fall outside the analytical phase, and the pre- and postanalytical steps have been found to be much more vulnerable. This collective paper, which is the logical continuum of the former already published in this journal 2 years ago, provides additional contribution to risk management in the preanalytical phase and is a synopsis of the lectures of the 2nd European Federation of Clinical Chemistry and Laboratory Medicine (EFLM)-Becton Dickinson (BD) European Conference on Preanalytical Phase meeting entitled "Preanalytical quality improvement: in quality we trust" (Zagreb, Croatia, 1-2 March 2013). The leading topics that will be discussed include quality indicators for preanalytical phase, phlebotomy practices for collection of blood gas analysis and pediatric samples, lipemia and blood collection tube interferences, preanalytical requirements of urinalysis, molecular biology hemostasis and platelet testing, as well as indications on best practices for safe blood collection. Auditing of the preanalytical phase by ISO assessors and external quality assessment for preanalytical phase are also discussed.

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

BACKGROUND

The aim of this study was to evaluate and compare the efficiency of high speed centrifugation and LipoClear® reagent for lipemia removal in plasma samples spiked with Intralipid®, for 26 biochemistry analytes.

MATERIALS AND METHODS

A plasma pool was collected. Aliquots of the pool were spiked with Intralipid® (final concentrations of 300mg/dL and 500mg/dL Intralipid®). The lipemia was removed from the aliquots by high speed centrifugation or LipoClear® reagent. 26 analytes were determined in native, lipemic plasma and in samples after lipemia removal. The bias from the concentration in the native sample was calculated for each parameter for Intralipid® concentrations, 300 and 500mg/dL of Intralipid®, respectively. Also, the recovery for each parameter after processing the samples using high speed centrifugation and LipoClear® was calculated. The biases and test recoveries were compared with the desirable specification for imprecision (DSI) according to Ricos available at the Wesgard's website. The bias and recovery for procalcitonin were compared with DSI according to Barassi and colleagues.

RESULTS

The bias of the spiked samples exceeded the DSI at 300mg/L Intralipid® for creatinine, glucose, total protein, iron and albumin; and for all previously mentioned parameters including CK-MB, sodium, potassium, chlorides, magnesium and ALP at concentration of 500mg/L Intralipid®. For the test recovery the DSI criteria were not met for calcium, total protein, sodium and chlorides after high speed centrifugation and for glucose, calcium, phosphates, magnesium, sodium, potassium, chlorides, ALP, GGT, CK-MB, total protein, albumin and troponin T after using LipoClear®.

CONCLUSIONS

LipoClear® is not suitable for lipemia removal from samples designated for glucose, sodium, potassium, chlorides, phosphates, magnesium, CK-MB, ALP, GGT, total protein, albumin, CRP and troponin T measurements. High speed centrifugation should be used for lipemia removal instead for glucose, potassium, phosphates, magnesium, CK-MB, ALP, GGT, albumin, CRP and TnT measurements.

Are patients well informed about the fasting requirements for laboratory blood testing?

Introduction:

Proper preparation of the individual is a key prerequisite for ensuring the quality of laboratory testing. Our hypothesis was that many outpatients are not sufficiently familiar with the correct way of preparing for the laboratory tests, for which the individual needs to be at fasting. This study aimed to investigate: i) whether patients are aware of how they need to prepare properly for laboratory tests; ii) the way in which users are informed about how to prepare for laboratory testing; and iii) whether users arrive to the laboratory for phlebotomy properly prepared.

Materials and methods:

An anonymous questionnaire was conducted on 150 outpatients older than 18 years, during February 2013. The response rate was 11%. All patients were interviewed by the laboratory staff. Patients were informed about detail of the questionnaire and agreed to participate in the survey.

Results:

Out of the total number subjects, 39% were fully aware of the proper definition of the fasting, whereas even 46% subjects replied that the last meal has to be taken the day before and the exact time that must pass after the last meal to blood sampling is not important. Furthermore, 52% subjects did not receive any information about how they need to prepare themselves properly for blood testing. Only 60% of them came properly prepared for the laboratory blood testing.

Conclusions:

Substantial proportion of patients do not come properly prepared for laboratory testing. We conclude that patients are not well informed about the fasting requirements for laboratory blood testing. Moreover, requesting physician is the preferred source of information from which patients learn how to prepare themselves for phlebotomy.

Heterogeneity of manufacturers' declarations for lipemia interference--an urgent call for standardization

INTRODUCTION

Due to the budget limitations, laboratories mostly rely on the manufacturers' information about the influence of interfering substances on laboratory results. However, some manufacturers do not follow the recommended procedures for testing interferences (CLSI standard) and there is a great variability in the presentation of data regarding lipemia interference.

MATERIALS AND METHODS

We aimed to verify the manufacturers' specifications for lipemia interference for clinical chemistry reagents provided by Beckman Coulter, Roche and Siemens. Bias was determined using the Intralipid® simulated lipemic samples. Furthermore, we aimed to compare obtained data with the manufacturers' claims and desirable specification for imprecision derived from biological variation.

RESULTS

i) Manufacturers' declarations were not confirmed for all three manufacturers; ii) the magnitude and direction of the effect of lipemia on laboratory results differ substantially between the three tested analytical systems; and iii) manufacturers are using arbitrary limits in declaring the expected effect of interference on laboratory results.

CONCLUSIONS

There is an urgent need to standardize the way manufacturers test and report their data on the lipemia interference. We propose that, instead of arbitrary limits, manufacturers use evidence based quality specifications for assessing the allowable biases. Moreover, laboratories should be aware of the possible lack of replicability of manufacturers' declarations.

Association of APOA5 -1131T>C polymorphism and serum lipid levels in patients with type 2 diabetes

Significant abnormalities in lipid metabolism are frequently present in patients with type 2 diabetes mellitus (T2DM). Hypertriglyceridemia, a highly proatherogenic state, is associated with increased risk of coronary artery disease. Genetic polymorphism APOA5 -1131T>C has been recognized as a significant contributor to hypertriglyceridemia in both healthy and diabetic populations. The aim of the study was to investigate the association of APOA5 -1131T>C polymorphism with the serum levels of triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol in patients with T2DM. In total, 234 DNA samples from patients with T2DM were genotyped using the PCR-RFLP method. Serum lipid levels were measured using standard laboratory methods. Obtained APOA5 -1131T>C genotype frequencies were 89% (T/T) and 11% (T/C+C/C). There was no significant association between APOA5 -1131T>C genotypes and triglyceride levels (1.90 mM [1.32-2.74] vs. 1.78 mM [1.54-3.05] for T/T vs. T/C+C/C genotype; p=0.553), HDL cholesterol levels (1.30 mM [1.10-1.40] vs. 1.30 mM [1.05-1.40] for T/T vs. T/C+C/C; p=0.534), and LDL cholesterol levels (3.1 mM [2.3-3.8] vs. 3.0 mM [2.2-3.5] for T/T vs. T/C+C/C; p=0.313). Our results suggest that hypertriglyceridemia in patients with T2DM is not likely to be associated with the APOA5 -1131T>C polymorphism.

Angiotensin-converting enzyme insertion/deletion polymorphism genotyping error: the cause and a possible solution to the problem

Rigat and colleagues were the first ones to develop a rapid PCR-based assay for identifying the angiotensin converting enzyme insertion/deletion (I/D) polymorphism. Due to a big difference between the length of the wild-type and mute alleles the PCR method is prone to mistyping because of preferential amplification of the D allele causing depicting I/D heterozygotes as D/D homozygotes. The aim of this study was to investigate whether this preferential amplification can be repressed by amplifying a longer DNA fragment in a so called Long PCR protocol. We also aimed to compare the results of genotyping using five different PCR protocols and to estimate the mistyping rate. The study included 200 samples which were genotyped using standard method used in our laboratory, a stepdown PCR, PCR protocol with the inclusion of 4 % DMSO, PCR with the use of insertion specific primers and new Long PCR method. The results of this study have shown that accurate ACE I/D polymorphism genotyping can be accomplished with the standard and the Long PCR method. Also, as of our results, accurate ACE I/D polymorphism genotyping can be accomplished regardless of the method used. Therefore, if the standard method is optimized more cautiously, accurate results can be obtained by this simple, inexpensive and rapid PCR protocol.

News at Biochemia Medica: research integrity corner, updated guidelines to authors, revised author statement form and adopted ICMJE Conflict-of-Interest Form

From the issue 23(1) we have implemented several major changes in the editorial policies and procedures. We hope that those changes will raise awareness of our potential authors and reviewers for research and publication integrity issues as well as to improve the quality of our submissions and published articles. Among those changes is the launch of a special journal section called Research Integrity Corner. In this section we aim to publish educational articles dealing with different research and publication misconduct issues. Moreover, we have done a comprehensive revision of our Instructions to authors. Whereas our former Instructions to authors have mostly been concerned with recommendations for manuscript preparation and submission, the revised document additionally describes the editorial procedure for all submitted articles and provides exact journal policies towards research integrity, authorship, copyright and conflict of interest. By putting these Guidelines into action, we hope that our main ethical policies and requirements are now visible and available to all our potential authors. We have also revised the former Authorship and copyright form which is now called the Author statement form. This form now contains statements on the authorship, originality of work, research ethics, patient privacy and confidentiality, and copyright transfer. Finally, Journal has adopted the ICMJE Form for Disclosure of Potential Conflicts of Interest. From this issue, for each submitted article, authors are requested to fill out the “ICMJE Form for Disclosure of Potential Conflicts of Interest” as well as the Author statement form and upload those forms during the online manuscript submission process. We honestly believe that our authors and readers will appreciate such endeavors. In this Editorial article we briefly explain the background and the nature of those recent major editorial changes.