Harmonization of indirect reference intervals calculation by the Bhattacharya method

OBJECTIVES

The aim of this study was to harmonize the criteria for the Bhattacharya indirect method Microsoft Excel Spreadsheet for reference intervals calculation to reduce between-user variability and use these criteria to calculate and evaluate reference intervals for eight analytes in two different years.

METHODS

Anonymized laboratory test results from outpatients were extracted from January 1st 2018 to December 31st 2019. To assure data quality, we examined the monthly results from an external quality control program. Reference intervals were determined by the Bhattacharya method with the St Vincent's hospital Spreadsheet firstly using original criteria and then using additional harmonized criteria defined in this study. Consensus reference intervals using the additional harmonized criteria were calculated as the mean of four users' lower and upper reference interval results. To further test the operation criteria and robustness of the obtained reference intervals, an external user validated the Spreadsheet procedure.

RESULTS

The extracted test results for all selected laboratory tests fulfilled the quality criteria and were included in the present study. Differences between users in calculated reference intervals were frequent when using the Spreadsheet. Therefore, additional criteria for the Spreadsheet were proposed and applied by independent users, such as: to set central bin as the mean of all the data, bin size as small as possible, at least three consecutive bins and a high proportion of bins within the curve.

CONCLUSIONS

The proposed criteria contributed to the harmonization of reference interval calculation between users of the Bhattacharya indirect method Spreadsheet.

Rapid and accurate method for quantifying busulfan in plasma samples by isocratic liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Objectives

Administration of busulfan is extending rapidly as a part of a conditioning regimen in patients undergoing hematopoietic stem cell transplantation (HSCT). Monitoring blood plasma levels of busulfan is recommended for identifying the optimal dose in patients and for minimizing toxicity. The aim of this research was to validate a simple, rapid, and cost-effective analytical tool for measuring busulfan in human plasma that would be suitable for routine clinical use. This novel tool was based on liquid chromatography coupled to mass spectrometry.

Methods

Human plasma samples were prepared using a one-step protein precipitation protocol. These samples were then resolved by isocratic elution in a C18 column. The mobile phase consisted 2 mM ammonium acetate and 0.1% formic acid dissolved in a 30:70 ratio of methanol/water. Busulfan-d₈ was used as the internal standard.

Results

The run time was optimized at 1.6 min. Standard curves were linear from 0.03 to 5 mg/L. The coefficient of variation (%CV) was less than 8%. The accuracy of this method had an acceptable bias that fell within 85-115% range. No interference between busulfan and the interfering compound hemoglobin, lipemia, or bilirubin not even at the highest concentrations of compound was tested. Neither carryover nor matrix effects were observed using this method. The area under the plasma drug concentration-time curves obtained for 15 pediatric patients who received busulfan therapy prior to HSCT were analyzed and correlated properly with the administered doses.

Conclusions

This method was successfully validated and was found to be robust enough for therapeutic drug monitoring in a clinical setting.

Performance evaluation of a point of care cartridge of the new GEM Premier ChemSTAT analyzer

Background and aims

GEM Premier ChemSTAT is a new point-of-care system providing rapid creatinine, BUN and tCO₂ measurements together with electrolytes, metabolites, hematocrit, pH and pCO₂ from a single whole blood specimen in acute care settings such as emergency departments and intensive care units. Accurate measurements of whole blood creatinine can aid in the diagnosis and treatment of renal diseases.

Materials and methods

Heparinized whole blood samples from different clinical locations were evaluated on the GEM Premier ChemSTAT and results compared to plasma from the same samples on the Beckman AU5800 or whole blood on the GEM Premier 4000. Precision studies were conducted with whole blood and quality control material.

Results

ChemSTAT correlated well with plasma samples on the AU5800 (regression slopes (S): 0.957–1.159, correlation coefficients (r)≥0.952) and with whole blood specimens on the GEM Premier 4000 (S: 0.9646–1.124, r ≥ 0.974). The repeatability was 0.1%–3.1% and QC precision were within lab and manufacturers’ specifications.

Conclusion

ChemSTAT demonstrated strong correlation to the comparative methods and excellent precision. Combining with its continuous quality management, ChemSTAT is suitable for acute care settings to provide rapid, reliable results, which could minimize time-to-treatment and improve patient outcome.

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GEM Premier ChemSTAT evaluated against Beckman AU 5800 and GEM Premier 4000.

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A multi-use cartridge-based system measures twelve analytes in whole blood sample.

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Method comparison and precision meet laboratory and manufacturers' specifications.

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Whole blood creatinine assays showed lab quality performance.

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Plasma vs serum bias observed for creatinine and urea on lab analyzer.

Indirect determination of biochemistry reference intervals using outpatient data

The aim of this study was to determine reference intervals in an outpatient population from Vall d'Hebron laboratory using an indirect approach previously described in a Dutch population (NUMBER project). We used anonymized test results from individuals visiting general practitioners and analysed during 2018. Analytical quality was assured by EQA performance, daily average monitoring and by assessing longitudinal accuracy between 2018 and 2020 (using trueness verifiers from Dutch EQA). Per test, outliers by biochemically related tests were excluded, data were transformed to a normal distribution (if necessary) and means and standard deviations were calculated, stratified by age and sex. In addition, the reference limit estimator method was also used to calculate reference intervals using the same dataset. Finally, for standardized tests reference intervals obtained were compared with the published NUMBER results. Reference intervals were calculated using data from 509,408 clinical requests. For biochemical tests following a normal distribution, similar reference intervals were found between Vall d'Hebron and the Dutch study. For creatinine and urea, reference intervals increased with age in both populations. The upper limits of Gamma-glutamyl transferase were markedly higher in the Dutch study compared to Vall d'Hebron results. Creatine kinase and uric acid reference intervals were higher in both populations compared to conventional reference intervals. Medical test results following a normal distribution showed comparable and consistent reference intervals between studies. Therefore a simple indirect method is a feasible and cost-efficient approach for calculating reference intervals. Yet, for generating standardized calculated reference intervals that are traceable to higher order materials and methods, efforts should also focus on test standardization and bias assessment using commutable trueness verifiers.

Assessing Liver Fibrosis Using the FIB4 Index in the Community Setting

Liver disease is frequently asymptomatic, challenging early identification in the primary care setting. The fibrosis 4 (FIB4) index is a liver fibrosis biomarker that is a potential alternative to liver biopsy for diagnosing and managing liver disease. This study aimed to calculate the FIB4 index for screening individuals at high risk of liver disease at the community level. This was a retrospective real-world study analyzing blood and serum test results from a central laboratory. The primary outcome was the number of individuals within each risk category for hepatic fibrosis: high risk (FIB4 ≥ 3.25) and low risk (FIB4 < 1.3). The analysis included samples from 31,753 patients, of which 18,102 were aged 40 to 75 years. In these patients, the FIB4 index had been explicitly requested in 1852 (10.2%) cases and estimated ad hoc in the rest. Of the 263 (1.5%) cases with FIB4 ≥ 3.25, the FIB4 index was requested in 46 (17.5%), and 52 (19.8%) showed evidence of liver fibrosis in their medical records, while the rest did not report any data regarding liver fibrosis. FIB4 is a simple score that can play a role as a "red flag" for early identification of patients at high risk of advanced liver fibrosis and their referral to specialized care.

Cross-sectional evaluation of circulating hepatitis B virus RNA and DNA: Different quasispecies?

BACKGROUND

Different forms of pregenomic and other hepatitis B virus (HBV) RNA have been detected in patients’ sera. These circulating HBV-RNAs may be useful for monitoring covalently closed circular DNA activity, and predicting hepatitis B e-antigen seroconversion or viral rebound after nucleos(t)ide analog cessation. Data on serum HBV-RNA quasispecies, however, is scarce. It is therefore important to develop methodologies to thoroughly analyze this quasispecies, ensuring the elimination of any residual HBV-DNA. Studying circulating HBV-RNA quasispecies may facilitate achieving functional cure of HBV infection.

AIM

To establish a next-generation sequencing (NGS) methodology for analyzing serum HBV-RNA and comparing it with DNA quasispecies.

METHODS

Thirteen untreated chronic hepatitis B patients, showing different HBV-genotypes and degrees of severity of liver disease were enrolled in the study and a serum sample with HBV-DNA > 5 Log₁₀ IU/mL and HBV-RNA > 4 Log₁₀ copies/mL was taken from each patient. HBV-RNA was treated with DNAse I to remove any residual DNA, and the region between nucleotides (nt) 1255-1611 was amplified using a 3-nested polymerase chain reaction protocol, and analyzed with NGS. Variability/conservation and complexity was compared between HBV-DNA and RNA quasispecies.

RESULTS

No HBV-DNA contamination was detected in cDNA samples from HBV-RNA quasispecies. HBV quasispecies complexity showed heterogeneous behavior among patients. The Rare Haplotype Load at 1% was greater in DNA than in RNA quasispecies, with no statistically significant differences (P = 0.1641). Regarding conservation, information content was equal in RNA and DNA quasispecies in most nt positions [218/357 (61.06%)]. In 102 of the remaining 139 (73.38%), HBV-RNA showed slightly higher variability. Sliding window analysis identified 4 hyper-conserved sequence fragments in each quasispecies, 3 of them coincided between the 2 quasispecies: nts 1258-1286, 1545-1573 and 1575-1604. The 2 hyper-variable sequence fragments also coincided: nts 1311-1344 and 1461-1485. Sequences between nts 1519-1543 and 1559-1587 were only hyper-conserved in HBV-DNA and RNA, respectively.

CONCLUSION

Our methodology allowed analyzing HBV-RNA quasispecies complexity and conservation without interference from HBV-DNA. Thanks to this, we have been able to compare both quasispecies in the present study.

A descriptive and validation study of a predictive model of severity of SARS-COV-2 infection

Objectives

The strain the SARS-COV-2 pandemic is putting on hospitals requires that predictive values are identified for a rapid triage and management of patients at a higher risk of developing severe COVID-19. We developed and validated a prognostic model of COVID-19 severity.

Methods

A descriptive, comparative study of patients with positive vs. negative PCR-RT for SARS-COV-2 and of patients who developed moderate vs. severe COVID-19 was conducted. The model was built based on analytical and demographic data and comorbidities of patients seen in an Emergency Department with symptoms consistent with COVID-19. A logistic regression model was designed from data of the COVID-19-positive cohort.

Results

The sample was composed of 410 COVID-positive patients (303 with moderate disease and 107 with severe disease) and 81 COVID-negative patients. The predictive variables identified included lactate dehydrogenase, C-reactive protein, total proteins, urea, and platelets. Internal calibration showed an area under the ROC curve (AUC) of 0.88 (CI 95%: 0.85-0.92), with a rate of correct classifications of 85.2% for a cut-off value of 0.5. External validation (100 patients) yielded an AUC of 0.79 (95% CI: 0.71-0.89), with a rate of correct classifications of 73%.

Conclusions

The predictive model identifies patients at a higher risk of developing severe COVID-19 at Emergency Department, with a first blood test and common parameters used in a clinical laboratory. This model may be a valuable tool for clinical planning and decision-making.

C1 esterase inhibitor and the contact system in COVID-19

Coronavirus disease 2019 (COVID-19) is frequently associated with severe systemic consequences, including vasculitis, a hyperinflammatory state and hypercoagulation. The mechanisms leading to these life-threatening abnormalities are multifactorial. Based on the analysis of publicly available interactomes, we propose that severe acute respiratory syndrome coronavirus-2 infection directly causes a deficiency in C1 esterase inhibitor, a pathogen-specific mechanism that may help explain significant systemic abnormalities in patients with COVID-19.

Mechanisms responsible for the altered cardiac repolarization dispersion in experimental hypothyroidism

AIMS

To identify the causes for the inhomogeneity of ventricular repolarization and increased QT dispersion in hypothyroid mice.

METHODS

We studied the effects of 5-propyl-2-thiouracil-induced hypothyroidism on the ECG, action potential (AP) and current density of the repolarizing potassium currents I(to,fast), I(to,slow), I(K,slow) and I(ss) in enzymatically isolated myocytes from three different regions of mouse heart: right ventricle (RV), epicardium of the left ventricle (Epi-LV) and interventricular septum. K(+) currents were recorded with the patch-clamp technique. Membranes from isolated ventricular myocytes were extracted by centrifugation. Kv4.2, Kv4.3, KChIP and Na/Ca exchanger proteins were visualized by Western blot.

RESULTS

The frequency or conduction velocity was not changed by hypothyroidism, but QTc was prolonged. Neither resting membrane potential nor AP amplitude was modified. The action potential duration (APD)(90) increased in the RV and Epi-LV, but not in the septum. Hypothyroid status has no effect either on I(to,slow), I(k,slow) or I(ss) in any of the regions analysed. However, I(to,fast) was significantly reduced in the Epi-LV and in the RV, whereas it was not altered in cells from the septum. Western blot analysis reveals a reduction in Kv4.2 and Kv4.3 protein levels in both the Epi-LV and the RV and an increase in Na/Ca exchanger.

CONCLUSION

From these results we suggest that the regional differences in APD lengthening, and thus in repolarization inhomogeneity, induced by experimental hypothyroidism are at least partially explained by the uneven decrease in I(to,fast) and the differences in the relative contribution of the depolarization-activated outward currents to the repolarization process.

Reduced calmodulin expression accelerates transient outward potassium current inactivation in diabetic rat heart

BACKGROUND/AIMS

In myocytes from diabetic hearts, the reduction in the amplitude of the transient outward potassium current (I(to)) and the acceleration of its inactivation contribute to the action potential duration lengthening. Whereas the reduced amplitude is attributable to a reduced support of trophic factors, the mechanism underlying the acceleration of inactivation remains unknown. Ca(2+)/Calmodulin-dependent protein kinase II (CaMKII) modifies the inactivation kinetics of I(to). In this work we explored the role of CaMKII in the acceleration of I(to) current inactivation observed in diabetic myocytes.

METHODS

We used patch-clamp and immunoblotting techniques in enzymatically-isolated myocytes from healthy and streptozotocin-induced diabetic rat hearts, and in blood samples from diabetic patients.

RESULTS

In control myocytes, inhibition of either calmodulin or CaMKII accelerated I(to) current inactivation. However, in diabetic myocytes I(to) inactivation was already accelerated, and did not respond to calmodulin or CaMKII inhibition. Calmodulin protein abundance was significantly reduced in diabetic myocytes. Incubation of diabetic myocytes with insulin recovered calmodulin expression to normal values. A similar pattern of calmodulin expression appears in the blood of diabetic patients. Insulin treatment also restored I(to) current inactivation kinetics as well as the responsiveness to regulation by calmodulin.

CONCLUSION

Diabetes-induced acceleration of I(to) current inactivation is due to a reduced effect of CaMKII on I(to) channels as a result of a diabetes-induced reduction in calmodulin protein expression. A correct follow up of the insulin treatment could prevent this alteration.

Type 1 diabetes alters brain cannabinoid receptor expression and phosphorylation status in rats

One of the most common symptoms of diabetes is extreme hunger, but the brain mechanism underlying this hyperphagia is unknown. The endocannabinoid system has emerged as one of the main food intake regulators in the brain. However, the effects of type 1 diabetes on the endocannabinoid system are not completely known. Thus, the aim of the present work is to establish the possible alterations induced by type 1 diabetes on the brain endocannabinoid system in rats. Western blot and immunocytochemistry were used to measure CB1 and phosphorylated CB1 receptor expression in several prosencephalic regions in streptozotocin-induced type 1 diabetic rats. Serum leptin levels were measured by ELISA. CB1 receptor expression was increased in striatum and hypothalamus of diabetic animals, with no changes in other brain areas studied. CB1 receptor phosphorylation was also increased in the same brain areas. Type 1 diabetes induced significant weight loss, and serum leptin levels were severely decreased. These results reinforce the possible role of the CB1 receptor as a pharmacological target for the clinical management of appetite in diabetic patients.

Diabetes-induced biochemical changes in central and peripheral catecholaminergic systems

A great variety of alterations have been described in the nervous system of diabetic animals. They are named as diabetic neuropathy and affect the brain, spinal cord and peripheral nerves. In diabetic animals, plasma and tissue catecholamine levels have been reported to be increased, decreased or unchanged, and these disparities have been explained by differences in the tissues selected, severity or duration of diabetes. Dopamine, norepinephrine and epinephrine from different tissues were extracted by absorption onto alumina, and measured by high performance liquid chromatography with electrochemical detection. We found that diabetes alters catecholaminergic systems in a highly specific manner. The dopamine content is reduced in the dopaminergic nigrostriatal system only. Norepinephrine is differently altered in several areas of the sympathetic nervous system. It is increased in cardiac ventricles, and decreased in stellate ganglia and the blood serum. However, it is not altered in the central nervous system. Finally, epinephrine is only altered in the adrenal gland where it is increased, and in the serum where it is reduced. Our results suggest that diabetes reduces the activity of the nigrostriatal dopaminergic system. Changes found at the sympathoadrenal level could be explained by reduced norepinephrine and epinephrine synthesis, with increased storage due to a reduced release from synaptic vesicles.

Virtual automation

Total laboratory automation (TLA) can be substituted in mid-size laboratories by a computer sample workflow control (virtual automation). Such a solution has been implemented in our laboratory using PSM, software developed in cooperation with Roche Diagnostics (Barcelona, Spain), to this purpose. This software is connected to the online analyzers and to the laboratory information system and is able to control and direct the samples working as an intermediate station. The only difference with TLA is the replacement of transport belts by personnel of the laboratory. The implementation of this virtual automation system has allowed us the achievement of the main advantages of TLA: workload increase (64%) with reduction in the cost per test (43%), significant reduction in the number of biochemistry primary tubes (from 8 to 2), less aliquoting (from 600 to 100 samples/day), automation of functional testing, drastic reduction of preanalytical errors (from 11.7 to 0.4% of the tubes) and better total response time for both inpatients (from up to 48 hours to up to 4 hours) and outpatients (from up to 10 days to up to 48 hours). As an additional advantage, virtual automation could be implemented without hardware investment and significant headcount reduction (15% in our lab).

Restoration of cardiac transient outward potassium current by norepinephrine in diabetic rats

In cardiac ventricle, the density of the transient outward potassium current, Ito, is clearly related to sympathetic nervous system integrity. This sympathetic regulation of Ito expression may be greatly significant to the genesis of cardiac complications of several diseases such us diabetes mellitus. Autonomic neuropathy, including cardiac neuropathy, is a complication of chronic diabetes. The objective of the present study was to identify the possible role of cardiac sympathetic neuropathy in the reduction of Ito current density in diabetic ventricular myocardium. Thus, we employed the patch-clamp technique to test whether Ito can be restored in diabetic myocytes incubated with norepinephrine. We also measured, using HPLC, the catecholamine content of the stellate ganglion, which is responsible for cardiac sympathetic innervation, in normal and diabetic animals. The main result of the present study was to show that a 24-h incubation of diabetic cells with norepinephrine restores Ito density to control values. The restoration of Ito current density by norepinephrine suggests that the diabetes-induced reduction of Ito is at least partially attributable to a reduced trophic effect of norepinephrine on the expression of Ito.

Effects of acute xylene exposure on the enkephalinergic neuromodulatory system in rats

Xylene is a neurotoxic organic solvent widely used in industry. However, the neurochemical mechanism of its action on the central nervous system is to date relatively unknown. In this work, the effect of subacute xylene exposure on met-enkephalin like immunostaining in different brain regions is described. Acute treatment with xylene generates a reduction in immunostaining for met-enkephalin in the globus pallidus, the olfactory tubercule and the hypothalamic medial preoptic area, without changes in the parietal cortex, caudatus-putamen and the central amygdaloid nuclei. It is suggested that enkephalins could play a role in xylene neurotoxic mechanism in the brain.

Lys- and Leu-aminopeptidase activity after acute toluene exposure in the rat brain

Changes in Lys- and Leu-aminopeptidase activities in several brain regions of the rat, after acute toluene administration, are described in this research. Aminopeptidase activity has been suggested as a candidate regulator of the degradation of several neuroactive peptides. Lys-aminopeptidase activity was significantly decreased in the thalamus, amygdala, and medulla oblongata. Leu-aminopeptidase activity was significantly decreased in the thalamus and cerebellum. It is suggested that these aminopeptidase activities could play a part in the mechanism of toluene neurotoxicity.

[Is the renin-angiotensin system implicated in the hypertensive effect of a water-soluble tissue extract?]

A deproteinized hydrosoluble splenic extract, which produces a hypertensive effect, injected in rats intravenously is described. The pressure action is very similar to the synthetic angiotensin II, and the (Sarcosine1-Isoleucine8)--angiotensin II, a competitive antagonist, produced partial inhibition of both responses. There were no significant differences between control and experimental rats in the plasmatic levels of angiotensin II, aldosterone and ADH. Therefore, the splenic extract does not seem to release these hormones included in the renin-angiotensin pathway. Significant Angiotensin II levels were detected in the splenic material. These results support the view that forty per cent of the pressure action is due to Angiotensin II present in the extract.

[Inhibiting effect of (sarcosine-1-isoleucine-8)-angiotensin II in anesthesized rats]

The peptidic sequence (Sarcosine-1-Isoleucine-8)-Angiotensin II has been demonstrated to be an in vitro specific and competitive antagonist of the Angiotensin II action. The present results show it to be a competitive antagonist also in vivo since pA2 values are similar, always reaches a 100% response on increasing the Angiotensin II dose, and when relating log (DR-1) and log dose of agonist, the slope is very near to one (0.925).

H1-histamine receptors may mediate the contractile response of guinea-pig ileum to 'histamine-free' splenic extracts

A water-soluble splenic factor, which produces a contractile response of the guinea-pig ileum, that is resistant to cholinoceptor and adrenoceptor antagonists is described. The ileal contractions elicited by the splenic extract showed some significant differences from those elicited by 5-hydroxytryptamine. The responses to splenic extract were not affected by the D-tryptamine-receptor antagonist, methysergide. The effect of the splenic extract on the guinea-pig ileum was similar to that of histamine. The H1-histamine antagonists, (+)-chloropheniramine and diphenhydramine, caused a parallel shift to the right of the splenic extract dose-response curve without suppression of the maximum response. A pA2 value of 8.97 +/- 0.03 for (+)-chloropheniramine and 7.55 +/- 0.1 for diphenhydramine was calculated. Significant histamine levels, as determined by fluorometric methods, could not be detected in the splenic extract. Likewise, the splenic factor did not release histamine from the intestinal preparation. These results support the view that: (i) the splenic factor acts through H1-histamine receptors; (ii) it is not histamine; (iii) it does not have any histamine releasing effect on the ileal smooth muscle.