Laboratory Errors Research Articles

Quantitative structure-properties relationship and molecular design of some anti-wear lubricant additives

In-silico QSPR and MD simulation methods were adopted to effectively design new lubricant anti-wear additive compounds as an alternative to zinc dialkyl dithiophosphate (ZDDP) which was reported to contribute to environmental pollution. Some QSPR linear models were developed out of which the best model (With statistical analysis R2 = 0.990, R2pred. = 0.818, R2adj = 0.979, R2cv = 0.748) was used to design three new additive structures with an improved anti-wear lubricant properties. Three lubricant additives such as 2-(hept‑1-en-2 ylthio)benzo[d]oxazole, 2-((5-methylhex-5-en-1-yl)thio)benzo[d]oxazole and 2-((5-methyl-2-methylenehex-5-en-1-yl)thio)benzo[d]oxazole were designed and revealed to have anti-wear properties of 0.593, 0.512, and 0.367 mm respectively. These anti-wear lubricant properties of all the designed additives were found to be better than the bench-mark anti-wear additive, ZDDP (3.284 mm) and what other researchers proposed. Moreover, The dynamic binding energies of all the designed anti-wear lubricant additives were found to be bound better than the one calculated by other researchers and was found to be excellently bound also than the commercially sold (benchmark additive) additive (ZDDP) 24,365.405. The addition of acceptor substituent like =CH2 groups to the hydrocarbon chain structures of all the newly designed additives was noticed to have improved lubricant wear-reduction properties and binding dynamic energies of the new additives on the simulated steel coated surface. Therefore, these QSPR and MD methods could be used to provide a theoretical framework for researchers and industrialists to design an improved anti-wear additive properties and save resources before expensive laboratory trial and error method.

Impact of time and temperature on gut microbiota and SCFA composition in stool samples.

Gut dysbiosis has been implicated in the pathophysiology of a growing number of non-communicable diseases. High through-put sequencing technologies and short chain fatty acid (SCFA) profiling enables surveying of the composition and function of the gut microbiota and provide key insights into host-microbiome interactions. However, a methodological problem with analyzing stool samples is that samples are treated and stored differently prior to submission for analysis potentially influencing the composition of the microbiota and its metabolites. In the present study, we simulated the sample acquisition of a large-scale study, in which stool samples were stored for up to two days in the fridge or at room temperature before being handed over to the hospital. To assess the influence of time and temperature on the microbial community and on SCFA composition in a controlled experimental setting, the stool samples of 10 individuals were exposed to room and fridge temperatures for 24 and 48 hours, respectively, and analyzed using 16S rRNA gene amplicon sequencing, qPCR and nuclear magnetic resonance spectroscopy. To best of our knowledge, this is the first study to investigate the influence of storage time and temperature on the absolute abundance of methanogens, and of Lactobacillus reuteri. The results indicate that values obtained for methanogens, L. reuteri and total bacteria are still representative even after storage for up to 48 hours at RT (20°C) or 4°C. The overall microbial composition and structure appeared to be influenced more by laboratory errors introduced during sample processing than by the actual effects of temperature and time. Although microbial activity was demonstrated by elevated SCFA at both 4°C and RT, SCFAs ratios were more stable over the different conditions and may be considered as long as samples are come from similar storage conditions.

Factors Affecting Quality of Laboratory Result During Ordering, Handling, and Testing of the Patient's Specimen at Hawassa University College of Medicine and Health Science Comprehensive Specialized Hospital.

BackgroundThe increase of medical laboratory test errors represents the increase of all defects within the process. An error can be any defect during the entire process, from ordering to reporting. It may have negative effects on patient care, by contributing to inappropriate treatment, an increase in lengths of hospital stay, and dissatisfaction with healthcare services. Therefore, this study aimed to determine factors affecting the quality of laboratory results through the entire process.MethodsA cross-sectional study was conducted at Hawassa University hospital from October 2018 to May 2019. Data were collected by using structured questionnaires and checklist and entered and analyzed using SPSS version 21. P-values less than 0.05 were considered statistically significant.ResultsA total of 455 individuals participated in this study. During the actual observational assessment, 72.5% of laboratory professionals identify their patients correctly and 62.5% of them label the sample before collection. In multivariate logistic regression, labeling of sample before collection (AOR=1.357, 95% CI=1.09, 1.58, P- 0.017), use of unmixed (AOR=4.364, 95% CI=1.950, 20.036, P- 0.049) and hemolyzed blood for testing (AOR=1.403, 95% CI=1.096, 1.692 P- 0.021) were associated with laboratory test errors. The clinical service providers who requested the test believed, lack of efficient laboratory service (P=0.005), unable to use manuals (P=0.025), and incorrect interpretation of reference booklets were associated with laboratory errors. Patient residence and frequency of first and second visits of the hospital were statistically associated with laboratory errors.ConclusionThe occurrence of laboratory errors in our study was demonstrated by the distribution pattern, the preanalytical, analytical, and post-analytical steps. But changes have occurred in the types and frequencies of errors in these phases of testing by laboratory professionals, clinicians, and patients in the current study. Therefore, the hospital administrations, laboratory professionals and clinicians should work harder and closer to solve the identified problems.

RETROSPECTIVE EVALUATION OF PRE-ANALYTICAL ERRORS IN CLINICAL BIOCHEMISTRY LABORATORY AT A TERTIARY CARE CENTRE IN RAJSAMAND, RAJASTHAN.

Background: This study was carried out to identify the causes of pre-analytical errors in the clinical biochemistry laboratory and their percentage occurrence so as to formulate the strategy for necessary corrective and preventive actions.
 Methods: A retrospective quantitative study was conducted in the department of biochemistry to identify the different causes of pre-analytical errors in the outpatient and inpatient samples. The sample rejection register and test requisition forms for the period of May 2018 to April 2019 were analysed and the percentage occurrence of the different types of errors was calculated.
 Results: Data analysis revealed that the occurrence of different errors was as follows: hemolysis (46.43%), sample not received (28.32%), insufficient quantity (8.16%), improper collection technique (7.14%), delayed transport (5.87%), wrong container (1.79%), sample clotted (1.28%), lipemic sample (0.77%) and sample exchanged during separation in lab (0.26%).
 Conclusion: The decline in the errors during the analytical phase of sample processing has shifted the focus towards reducing errors occurring in the pre-analytical phase. This is necessary to ensure patient safety.
 Keywords: Pre-analytical errors, Biochemistry, hemolysis.

Effects of calcium dobesilate (CaD) interference on serum creatinine measurements: a national External Quality Assessment (EQA)-based educational survey of drug-laboratory test interactions

Drug-laboratory test interactions (DLTIs) are one of the major sources of laboratory errors. Calcium dobesilate (CaD) interference on serum creatinine testing is a widespread problem that has long been ignored in China. A national EQA-based survey was launched to investigate the current status of CaD interference on creatinine routine methods used in China and enhance the education of CaD interference in clinical laboratories. A descriptive survey was developed to characterize the status quo of Chinese laboratory professionals' cognition to CaD interference. Four of survey samples which were spiked with/without interference additive were shipped to 175 participant laboratories. The target reference values from a reference measurement procedure were compared against the results from participating laboratories to evaluate the CaD interference on serum creatinine measurements using enzymatic method or Jaffé method. The lack of knowledge of DLTIs and the barriers to collect information from pharmacological and laboratory data systems had become the main problems on implementing DLTIs education in China. A significant negative influence of CaD on enzymatic method was observed regardless of measurement platforms. Jaffé method was generally free from interaction with CaD but showed poor precision and accuracy at low creatinine concentrations. More efforts should be made to enhance the education of DLTIs in clinical laboratories in China.

Uromodulin – biomarker of renal function with promising clinical application

Uromodulin (also known as Tamm-Horsfall protein) is a glycoprotein produced exclusively in the kidneys, mainly in the epithelial cells of the thick ascending limb of the loop of Henle. Under physiological conditions, it is the most abundant urinary protein. A small proportion is released into the renal interstitium and then into the blood, where it can be detected and used as a potential parameter of renal function. Uromodulin has numerous physiological roles and potential pathogenetic significance, including providing protection against urinary tract infections and the formation of urinary deposits, as well as being involved in the immunomodulatory functions and regulation of water and electrolyte balance by the kidneys. Unlike classic renal markers (such as creatinine), uromodulin levels decrease with progressive renal dysfunction. A significant advantage of this parameter is therefore the detectable changes in concentration at the early stages of development of chronic kidney disease. In addition, assessment in clinical materials, such as urine and blood, is relatively simple by immunoenzymatic methods. It is evident that the quantitative determination of uromodulin in blood serum is associated with a lower risk of laboratory error and has a better correlation with renal function. Based on previous studies, Tamm-Horsfall protein / uromodulin can be considered a valuable parameter for standard diagnostics of kidney function and renal diseases. It appears that no other marker is currently able to reflect the integrity and functional state of the renal tubules as sensitively as uromodulin. Due to the potential of this parameter, the article presents and overview of the current information available about uromodulin, as well as the available diagnostic tests and the frequency of their use in clinical practice.

Modeling of Screw-Dental Structure Interaction: First Step Toward Finite Element Analysis

This research is focused on the screw-structure interaction under dynamic impulses aimed to the contact analysis of gap propagation at dental implant-abutment interface under dynamic loading. The purpose is to investigate the fracture mechanism that occurs during the screw penetration in a support and during the support vibration. Numerical Finite Element (FEM) analyses are calibrated through experimental laboratory measurements on support materials and screws typologies. Uncertainty due to the laboratory error propagation is investigated using Polynomial Chaos Expansion (PCE) of experimental measurements. The research is planned through the following steps: FEM calibration trough laboratory experiments on materials; laboratory experiments and material mechanics identification; uncertainty error propagation analysis through PCE expansion; fragility curves for numerical model calibration; FEM models calibration trough laboratory measurements on cycling loads. Therefore, the main purpose of the research activity, of which this article constitutes a preliminary and an explorative step, is to study a methodology that minimizes the local damage of the dental material due to the generation of micro-cracks following the implantation actions. Accordingly, in this paper, preliminary results are reported.

Errors within the total laboratory testing process, from test selection to medical decision-making - A review of causes, consequences, surveillance and solutions.

Laboratory analyses are crucial for diagnosis, follow-up and treatment decisions. Since mistakes in every step of the total testing process may potentially affect patient safety, a broad knowledge and systematic assessment of laboratory errors is essential for future improvement. In this review, we aim to discuss the types and frequencies of potential errors in the total testing process, quality management options, as well as tentative solutions for improvement. Unlike most currently available reviews on this topic, we also include errors in test-selection, reporting and interpretation/action of test results. We believe that laboratory specialists will need to refocus on many process steps belonging to the extra-analytical phases, intensifying collaborations with clinicians and supporting test selection and interpretation. This would hopefully lead to substantial improvements in these activities, but may also bring more value to the role of laboratory specialists within the health care setting.

Interbreeding between archaic human groups and anatomically modern humans commonly occurring in prehistory

A hominin bone fragment from Denisova Cave (Russia) was identified among very few archaic human specimens (i.e., Neanderthals and Denisovans) as being the first-generation offspring of a Neanderthal mother and a Denisovan father. The ancient genomic study of this individual, together with previous evidence of interbreeding, suggests that admixture between archaic and modern humans was common. Here, we review the evidence for hominin interbreeding and the impact of introgressed archaic human DNA on modern humans. As the recovery of human remains in the Pleistocene is extremely rare, a collagen fingerprinting method, often referred to as Zooarchaeology by Mass Spectrometry (ZooMS), was applied to identify over 2000 fragmented bones from Denisova Cave with one being of hominin origin. This individual, named Denisova 11, had her genome sequenced to an average coverage of 2.6-fold. Her mitochondrial DNA was found to be of the Neanderthal type and direct radiocarbon dating showed her to be more than 50000 years old. Approximately equal proportions of Neanderthal-like and Denisovan-like alleles were found in the Denisova 11 individual. This can be explained by her belonging to a population with mixed Neanderthal and Denisovan ancestry, or by her parents being from each one of these two groups. After excluding any accidental mixing of DNA in the laboratory or systematic errors in data processing, analysis of the individual’s alleles carried by two randomly drawn DNA fragments indicated that she had a Neanderthal mother and a Denisovan father. Interbreeding between archaic and modern humans outside Africa was confirmed by a series of studies since the draft sequence of the Neanderthal genome was published in 2010; non-Africans today are the products of this mixture. The proportion of Neanderthal ancestry is significantly higher in present-day East Asians (2.3%−2.6%) than in Western Eurasians (1.8%−2.4%). This has been explained by two independent Neanderthal gene flow events, a later out-of-Africa migration that diluted the proportion of Neanderthal ancestry in Western Eurasian ancestors, or by purifying selection in different population groups. A recent study found that African populations have more Neanderthal ancestry than previously thought, which can be explained by back-migration of Europeans carrying Neanderthal ancestry into Africa. Another widely-known archaic human group, the Denisovans, was identified by the ancient DNA extracted from a finger bone found in Denisova Cave. Along with the high proportion (~5%) of ancestry contributed to present-day Melanesians in Oceania, Denisovans also contributed ~0.2% to the ancestry of mainland Asian and Native American populations. Genes flow into Denisovans from Neanderthals and an unknown hominin (“super-archaic”) were also suggested by ancient DNA studies. Archaeological, ancient genomic, and ancient protein studies suggest Denisovans may have had a wide ecological and geographic distribution. Overall, frequent admixture among different human groups resulted in ~2% Neanderthal ancestry in all non-African humans and up to 5% Denisovan ancestry in some present-day Oceanians. The introgressed archaic human DNA in present-day humans have been affected by natural selection, and inferences about the functional, evolutionary, and phenotypic significance reveal both positive and negative effects. Functional regions of modern human genomes have fewer archaic alleles than expected under a neutral demographic model, which suggests a reduced fitness of some archaic alleles in modern humans. Many Neanderthal variants associated with phenotypes and susceptibility to diseases have been identified in present-day non-Africans, such as type 2 diabetes, lupus, biliary cirrhosis, etc. However, many of the introgressed tracts are also functionally important and possibly helped modern humans adapt to different environments, such as high altitude and latitude areas. For example, the EPAS1 and WARS2/TBX15 , are associated with a high-altitude and high-latitude adaptation in Tibetans and Greenlandic Inuits, respectively. These findings illustrate that admixture with archaic humans has provided genetic variation that helped humans adapt to new environments and has continued to shape our biology. We expect that in the future there will be more evidence of interbreeding between humans in different areas and time periods, adding more details to human genetic history.

Medical safety reporting system neccessity and analysis of Turkey 2016 data: A health policy report.

The National Safety Reporting System, which is developed for Turkey, aims to classify medical errors with a coding methodology that handles errors in subcategories. Error entries done via the system are added to the statistics immediately by advanced live data reporting capabilities of the software. Our aim was to provide information about the Turkey local reporting system to ensure patient safety by detecting medical errors. The data used for analyses were obtained from https://www.grs.saglik.gov.tr and the web service used by hospital information systems. The error reporting time, most commonly reported errors, errors by professions and errors by location were examined under the major error categories and percentages that have been used in relevant data. In total, 53,477 errors were submitted to the National Safety Reporting System in 2016. When these entries were split into relevant categories such as drug errors, laboratory errors, surgical errors and patient safety errors, the most common errors were wrong dosage order, hemolyzed sample, not marking the side to be operated on and patient fall (patient/caretaker related), respectively. In order to reduce medical errors and provide patient safety, every institution must first of all do its own self-assessment. New user-friendly systems can be developed in order to increase medical error notifications and thus institutions can improve their healthcare quality.

The Dangers of Convictions Based on a Single Piece of Forensic Evidence

The overall goal of the criminal justice system is to ensure that perpetrators of crimes are duly punished and that victims of crimes are duly exonerated. As part of the effort to achieve this goal, the forensic disciplines have become very important in criminal investigations and prosecutions in identifying the guilty and in exonerating the innocent. There is a growing number of cases where people have been convicted based on a single piece of forensic evidence. However, some of the convictions have been found to be wrong, largely, due to the lack of adequate scientific validation of the forensic science methods. Some of these methods include latent fingerprint analysis, bite mark analysis, microscopic hair analysis and firearms identification. This article critically examines the application of forensic evidence in criminal prosecutions and highlights the dangers of convictions based on a single piece of forensic evidence. The findings of recent reports, such as, the National Academy of Sciences (NAS) 2009 Report and President's Council of Advisors on Science and Technology (PCAST) 2016 Report, confirm the critical role and broad scope of these forensic pattern-matching methods. The reports also indicate flaws that affect the accuracy of these methods, such as, inadequate scientific validation, coincidental results (erroneous match), human, laboratory and interpretive errors etc. Therefore, this article argues that the court should follow a cautionary approach when relying on a single piece of forensic evidence and that strong corroboration with other forms of evidence linking the accused to the crime should be required.

Laboratory errors for identification of the escherichia coli strains of the serological groups O6 and O25 as acute intestinal infections.

Were studied the genes encoding the virulence factors of 221 strains: E. coli O6:H1 (194) and E. coli O25:H4 (27), isolated in 2014-2018 from stool samples of children and adults examined according to epidemic indications. Molecular methods included PCR with hybridization-fluorescence and electrophoresis detection of amplified products. The strains did not have virulence genes for diarrheagenic E. coli (DEC) pathogroups EPEC, ETEC, EIEC, EHEC, EAggEC, and belonged to the phylogenetic group B2. They contained from four to eight genes encoding virulence factors of ExPEC: E. coli O6:H1 - pap (68,6%), sfa (87,6%), fimH (96,4%), hly (62,4%), cnf (74,7%), iutA (97,9%), fyuA (95,9%), chu (100%); E. coli O25:H4 - pap (66,7%), afa (22,2%), fimH (100%), hly (44,4%), cnf (44,4%), iutA (100%) , fyuA (100%), chu (100%). The antimicrobial susceptibility testing to 6 classes of antimicrobials (beta-lactams, fluoroquinolones, aminoglycosides, nitrofurantoin, sulfanilamide, trimethoprim / sulfamethoxazole) according the EUCAST. 60,3% of E. coli O6:H1 were sensitive to antibiotics, E. coli O25:H4 remained sensitive to carbapenems and nitrofurans. Extended-spectrum cephalosporins resistance was due to the production ESBL (CTX-M). The 57,1% resistant strains of E. coli O6:H1 and 100% of E. coli O25:H4 strains belonged to the MDR phenotype. The XDR phenotype had one in five MDR strains of E. coli O6:H1 and E. coli O25:H4. All strains of E. coli O25:H4 belonged to ST131. Given the important role of E. coli in human pathology, detection of virulence genes should be performed to confirm the etiological significance of the isolated strain.

MON-481 Remarkable Euthyroid Hyperthyroxinemia Mistaken for Thyrotoxicosis

CLINICAL CASEA 46 year old caucasian female with past medical history of menorrhagia was referred from primary care for evaluation of thyrotoxicosis. Thyroid function was assessed in the context of menometrorrhagia. She did not have any history of thyroid disorder or abnormal thyroid function tests. Per outside records, recent labs demonstrated TSH 0.88 uIU/mL (0.36-3.74), Free T4 > 8.00 ng/dL (0.76-1.46), Free T3 2.9 pg/mL (2.18-3.98). All other labs were within normal limits. Thyroid ultrasound revealed normal parenchyma and volume. She did not take any medications or supplements including biotin. She denied heat intolerance, anxiety, palpitations, dyspnea, tremors, hyperdefecation, or change in hair, skin, or mood. No epiphora, diplopia, or eye irritation was reported. Her father had been diagnosed with hyperthyroidism, mother with hypothyroidism.Repeat labs at our visit revealed normal TSH of 1.05 uIU/mL (0.358- 3.74), normal Free T3 2.58 pg/mL (2.18- 3.98), normal Total T3 136 ng/dL (80-200), elevated Free T4 >8.00 ng/dL (0.76-1.46) and elevated Total T4 11.6 ug/dL (4.5-10.5). These lab values were not consistent with patient’s euthyroid clinical status, prompting assessment of Free T4 by dialysis, normal at 1.5 ng/dL (0.9-2.2) and T3 uptake, high at 40% (24-39%). This picture was consistent with Familial Dysalbuminemic Hyperthyroxenemia (FDH). The decision was made not to treat the patient with anti-thyroid medications and to perform a confirmatory genetic testing to test for mutations in the ALB (albumin) gene.DISCUSSIONThe free T4 assay used by our institution is performed on the Siemens Dimension Vista platform using a two-step chemiluminescent immunoassay. While in theory two-step assays should not yield abnormal results in FDH, several two-step assays are known to yield falsely high results in patients with FDH (1, 2, 3).Other potential etiologies for discordant Free T4 levels include thyroid hormone autoantibodies, heterophile antibodies, biotin use, and anti-streptavidin antibodies (3).CONCLUSIONRecognition of laboratory error in the workup of thyroid disease is essential. Clinicians must ensure thyroid function labs are consistent with each other and with the patient’s presentation. In such cases misdiagnosis of hyperthyroidism or thyroid hormone resistance may lead to unnecessary testing and inappropriate treatment (3).

MON-220 Real World Performance of Urinary and Plasma Metanephrine Assays in Diagnosing Phaeochromocytoma/Paraganglioma

Introduction:Diagnosis of pheochromocytoma/paraganglioma (PPGL) can be challenging. Plasma metanephrines have highest sensitivity (96-99%) yet lowest specificity (85%)1 whereas 24-hour urinary metanephrines have 87.5% sensitivity and 99.7% specificity. Diagnostic accuracy depends on factors such as patient positioning and medications, questioning its potential value in a hospital setting.Methods:The audit was performed in a hospital which caters to a population of 400,000. Data was collected retrospectively on patients who had a request for plasma or urine metanephrines from March 2018 – September 2018.Results:A total of 85 patient order requests (58% male, 42% female) were reviewed; only 2 patients were ultimately diagnosed with a pheochromocytoma.The mean age of patients was 48 years. The most common indication for requests was hypertension (64 patients).Locations of order requests included 42% from outpatient clinics, 32% inpatient requests, 18% from Ambulatory Care, 6% by A&E and 2% by GP. Of the 27 (32%) inpatient requests, 10 had positive results: 1 diagnosed with primary aldosteronism, 1 with hypercortisolism and the others had no definite diagnosis. 8/10 patients with positive results did not have a repeat test.Focusing on plasma metanephrines, 52% plasma metanephrines samples were negative, 22% were positive and 26% were not processed due to laboratory error. From the 19 positive plasma metanephrines, adrenal adenoma was present in 7 patients (from this group, 1 was referred for surgery with confirmed diagnosis of pheochromocytoma), 1 patient’s MIBG scan was negative and 1 diagnosis of stress-related raised metanephrines was made. The remaining 10 patients did not undergo an adrenal scan.9 out of 18 cases with positive urine metanephrines had an adrenal adenoma. In 7/9, plasma metanephrines were positive, the remaining 2 had negative plasma metanephrines.34 cases with initial negative test still had another urine/plasma metanephrines performed with similar negative result. Furthermore <50% of the positive urine or plasma metanephrines were referred to and reviewed by the Endocrine team.Discussion:This audit highlights the potential pitfalls of investigating PPGL with plasma and urinary metanephrines, and in fact raises the question of its accuracy as an inpatient diagnostic tool as none of the positive inpatient tests resulted in a diagnosis of PPGL. Inappropriate urine and plasma metanephrines requests cause financial burden and patient anxiety. Even with outpatient requests, few positive results led to a PPGL diagnosis. Patient selection and conditions of testing must be more rigorously scrutinised and threshold for positive result must be raised for specificity of the test to be improved in ‘real world’ conditions.

Detection of Falsely Elevated Point-of-Care Potassium Results Due to Hemolysis Using Predictive Analytics.

Preanalytical factors, such as hemolysis, affect many components of a test panel. Machine learning can be used to recognize these patterns, alerting clinicians and laboratories to potentially erroneous results. In particular, machine learning might identify which cases of elevated potassium from a point-of-care (POC) basic metabolic panel are likely erroneous. Plasma potassium concentrations were compared between POC and core laboratory basic metabolic panels to identify falsely elevated POC results. A logistic regression model was created using these labels and the other analytes on the POC panel. This model has high predictive power in classifying POC potassium as falsely elevated or not (area under the curve of 0.995 when applied to the test data set). A rule-in and rule-out approach further improves the model's applicability with a positive predictive value of around 90% and a negative predictive value near 100%. Machine learning has the potential to detect laboratory errors based on the recognition of patterns in commonly requested multianalyte panels. This could be used to alert providers at the POC that a result is suspicious or used to monitor the quality of POC results.

Frequency and classification of errors in laboratory medicine at a veterinary teaching hospital in the United States.

The accuracy of laboratory data is of utmost importance. Data regarding laboratory error in human laboratories are often extrapolated into veterinary settings. One study investigated the rate and type of errors in a European commercial veterinary laboratory, but that data might not directly apply to an educational setting. This study determined the frequency and type of errors in laboratory medicine at a veterinary teaching hospital. Errors associated with clinical pathology samples were recorded over two 60-day periods. The first period included a time when new students and house officers started at the veterinary school. The second time period was 6months later. The errors were assigned to categories, and the frequency of each was calculated. Sample hemolysis, icterus, and lipemia were evaluated separately using an automated index, as these conditions could be pathologic or the result of error. Frequencies of error and hemolysis, icterus, and lipemia were assessed between the groups. Total error rates were 4.7% and 3.5% for the first and second periods, respectively. The frequency of each error subclassification was similar to those observed in the veterinary and human literature, with preanalytic error predominating. Statistically significant differences in the overall error rate and percentage of preanalytic errors that occurred outside of and within the laboratory were observed comparing differences between the two periods. The overall error rate in this veterinary teaching hospital was slightly higher than that previously reported in other settings, although a proportion of errors was as expected. Areas needing improvement were identified, and strategies to reduce error could be developed.

A Novel Approach to Atomistic Molecular Dynamics Simulation of Phenolic Resins Using Symthons.

Materials science is beginning to adopt computational simulation to eliminate laboratory trial and error campaigns—much like the pharmaceutical industry of 40 years ago. To further computational materials discovery, new methodology must be developed that enables rapid and accurate testing on accessible computational hardware. To this end, the authors utilise a novel methodology concept of intermediate molecules as a starting point, for which they propose the term ‘symthon’ (The term ‘Symthon’ is being used as a simulation equivalent of the synthon, popularised by Dr Stuart Warren in ‘Organic Synthesis: The Disconnection Approach’, OUP: Oxford, 1983.) rather than conventional monomers. The use of symthons eliminates the initial monomer bonding phase, reducing the number of iterations required in the simulation, thereby reducing the runtime. A novel approach to molecular dynamics, with an NVT (Canonical) ensemble and variable unit cell geometry, was used to generate structures with differing physical and thermal properties. Additional script methods were designed and tested, which enabled a high degree of cure in all sampled structures. This simulation has been trialled on large-scale atomistic models of phenolic resins, based on a range of stoichiometric ratios of formaldehyde and phenol. Density and glass transition temperature values were produced, and found to be in good agreement with empirical data and other simulated values in the literature. The runtime of the simulation was a key consideration in script design; cured models can be produced in under 24 h on modest hardware. The use of symthons has been shown as a viable methodology to reduce simulation runtime whilst generating accurate models.

Response to Zhao and Zhou: Diagnosis of HIV infection in breastfed infants of mothers on antiretroviral therapy.

We thank Zhao and Zhou [1] for their thoughtful comments on our report of two infants born to women with HIV who had unusual trajectories of diagnostic tests. The two HIV-exposed infants were initially positive on nucleic acid amplification tests in the first month of life but had multiple negative tests during breastfeeding and presented with definitive evidence of HIV infection around the time of breastfeeding cessation. We hypothesize that constituents of breast milk, or processes induced by breastfeeding, most likely in combination with antiviral effects of maternal antiretroviral therapy, led to the undetectable test results that we observed in already infected infants until breastfeeding ended. We considered the alternative explanation of postnatal transmission proposed by Zhao and Zhou [1], but this explanation requires dismissing the initial positive test results on the early samples as transient infections or false-positive results. A rigorous investigation of 42 cases of suspected transient infection, failed to confirm a single one, despite the plausibility of this concept [2]. In one of the infants in our report, virus was detected in peripheral blood mononuclear cells (PBMCs) from three separate blood samples collected over the first month of life making laboratory errors an unlikely explanation. In this same case, CD4+ T cells from one of these early age time points were found to be positive for 2-LTR episomal HIV-1 DNA. Detection of 2-LTR episomal DNA in CD4+ T cells, although at low levels, provides evidence of viral replication as these episomal circles are a by-product thereof [3]. We acknowledge that early samples were not available for the second case making the alternative explanation of an initial false-positive result followed by postnatal infection a possible explanation of this second case. It should be noted that current birth testing and early treatment guidelines in South Africa would provide indefinite treatment to transient infections should they occur [4]. We would like to clarify the implications of our observations in the context of current guidance around antiretroviral use for women and their children to prevent vertical transmission of HIV. Maintenance of maternal therapeutic antiretroviral drug regimens over the full duration of breastfeeding and beyond is now considered standard of care for prevention of HIV transmission to children. This recommendation is consistent with clinical trials demonstrating exceptionally low rates of postnatal transmission if effective maternal antiretroviral drug treatment is in place [5]. Longer term infant prophylaxis is recommended only for infants whose mothers initiated treatment late and/or who are nonadherent with treatment. In both cases, maternal viral loads through the breastfeeding period were less than 1000 RNA copies/ml and in-country treatment guidelines were followed in terms of prophylactic regimens [6]. Because of concerns that infant prophylaxis may mask underlying HIV infections, some have encouraged repeat testing after prophylaxis has ended [7]. What distinguishes our cases is that the pattern of negative results was observed after discontinuation of antiretrovirals given to the infants but during continuation of maternal antiretroviral treatment and breastfeeding. Although the profile of the results that we observed is rare, we support repeat testing of HIV-exposed breastfed infants after complete cessation of all breastfeeding. The profile of HIV antibodies is of great interest, but it is unlikely that changes in standard anti-HIV IgG antibody titres over time in these infants will be helpful to resolve the timing of transmission. Infant antiretroviral prophylaxis. and on-going antiretroviral exposure via breast milk, like early treatment, may lead to undetectable antibodies [8]. The ability to detect HIV antibody would probably be at the time when these factors are no longer in place and viral levels rise and drive antibody production. Thus, a rise in antibodies, only once breastfeeding has stopped, might not necessarily mean the children were infected later. More sensitive assays differentiating antibody isotypes and antigen specificity may be more informative but will need comparison with the usual profile of antibodies in HIV-exposed uninfected children. The utility of HIV antibodies as markers of viral processes is well appreciated and this is likely to be a productive, albeit complex, line of research. Acknowledgements Conflicts of interest There are no conflicts of interest.

Quality Assurance in Medical Laboratories in Developing Countries: Assessment of Pre-Analytical Errors in a Chemical Pathology Laboratory in a Tertiary Hospital in Nigeria

Quality Assurance in Medical Laboratories in Developing Countries: Assessment of Pre-Analytical Errors in a Chemical Pathology Laboratory in a Tertiary Hospital in Nigeria

External Quality Assessment Schemes for Biomarker Testing in Oncology: Comparison of Performance between Formalin-Fixed, Paraffin-Embedded–Tissue and Cell-Free Tumor DNA in Plasma

Liquid biopsies have emerged as a useful addition to tissue biopsies in molecular pathology. Literature has shown lower laboratory performances when a new method of variant analysis is introduced. This study evaluated the differences in variant analysis between tissue and plasma samples after the introduction of liquid biopsy in molecular analysis. Data from a pilot external quality assessment scheme for the detection of molecular variants in plasma samples and from external quality assessment schemes for the detection of molecular variants in tissue samples were collected. Laboratory performance and error rates by sample were compared between matrices for variants present in both scheme types. Results showed lower overall performance [65.6% (n=276) versus 89.2% (n=1607)] and higher error rates [21.0% to 43.5% (n=138) versus 8.7% to 16.7% (n=234 to 689)] for the detection of variants in plasma compared to tissue, respectively. In the plasma samples, performance was decreased for variants with an allele frequency of 1% compared to 5% [56.5% (n=138) versus 74.6% (n=138)]. The implementation of liquid biopsy in the detection of circulating tumor DNA in plasma was associated with poor laboratory performance. It is important both to apply optimal detection methods and to extensively validate new methods for testing circulating tumor DNA before treatment decisions are made.