Comparison of blood gas, electrolyte and metabolite results measured with two different blood gas analyzers and a core laboratory analyzer

Performance Evaluation of the i-SmartCare 10 Analyzer and Method Comparison of Six Point-of-Care Blood Gas Analyzers

Blood gas, electrolyte, glucose, and lactate level measurement have an immediate and critical impact on patient care. We evaluated the performance of i-SmartCare 10 (i-SENS Inc., Seoul, Korea) and conducted a method comparison study of five point-of-care (POC) analyzers with i-SmartCare 10 as the comparator, according to the CLSI guidelines. Ten analytes (pH, pCO₂, pO₂, Na⁺, K⁺, Cl^-, iCa²⁺, glucose, lactate, and Hct) were tested on six analyzers: i-SmartCare 10, ABL90 FLEX PLUS (Radiometer Medical ApS, Copenhagen, Denmark), i-Stat (Abbott Point of Care Inc., Princeton, NJ, USA), RapidLab 1265 (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), Stat Profile pHOx Ultra (Nova Biomedical, Waltham, MA, USA), and Gem Premier 5000 (Instrumentation Laboratory, Bedford, MA, USA). The total imprecision and linearity (r²>0.99) were excellent, except for a few analytes that narrowly escaped the preset criteria. Interference was noted for Na⁺ in the presence of a high K⁺ level and for iCa²⁺ in the presence of high K⁺ and Mg²⁺ levels. Forty of 48 items demonstrated either a proportional or systematic difference in regression analysis; the relative mean difference (%) of 14/48 items escaped the allowable total error in the difference plot analysis. i-SmartCare 10 shows acceptable performance, and using a single POC blood gas analyzer is recommended for monitoring.

Pseudohyperkalemia Associated With Leukemia

Elevated potassium levels can be a life-threatening emergency. We describe a case of falsely elevated serum potassium level in a patient with leukemia, which was suspected to be falsely elevated because the patient was asymptomatic with a normal electrocardiogram (EKG). Common reasons behind such a discrepancy in leukemia patients are the use of a tourniquet before collection, use of vacuum/pneumatic tubes for transportation, prolonged periods of incubation, use of heparin for sample collection, and processing of samples via centrifugation. Since the process is related to the method of collection and processing, we recommend using rapid point of care testing in such cases to differentiate between false and true potassium elevation, as it is a well-validated tool. Moreover, there is a good correlation between potassium measured with the blood gas, point of care, and central laboratory analyzers when the concentration of potassium is above 3 mEq/L.

Blood-gas vs. Central-Laboratory analyzers: interchangeability and reference intervals for sodium, potassium, glucose, lactate and hemoglobin

Background

Blood-Gas Analyzers (BGAs) are commonly used in parallel with central laboratory analyzers (CLAs). Given the often-divergent results between BGAs and CLAs this study aims to: 1. Determine whether the measurements of potassium (K), sodium (Na), glucose (Glu), lactate (Lact) and total hemoglobin (ctHb) on BGAs and CLAs are interchangeable; 2. Establish reference intervals (RIs) for both analyzer systems using an indirect statistical approach.

Methods

During a one-year study period K, Na, Glu, Lact and ctHb measurements from 500 arterial blood samples, measured on ABL 90 FLEX BGAs were compared with corresponding venous samples measured on Roche c8000 and Sysmex XN-9000 analyzers. Interchangeability of methods was tested based on the Acceptable Change Limit, Total Change Limit and the guidelines published by the German Medical Association for quality assurance in medical laboratories criteria. Indirect RIs were estimated based on all routine analysis data using the software Reference Limit Estimator (RLE).

Results

With the exception of Na, the BGAs differed significantly from the CLAs for the tested analytes (P < 0.001) but, with the exception of ctHb, did meet the interchangeability criteria. For K, Na, Gluc and ctHb the reference intervals obtained with RLE did not differ statistically between the analyzer systems.

Conclusion

The interchangeability criteria were met for Na, K and Gluc and Lact. The indirect RIs obtained with RLE, are comparable between two systems for Na, K, Gluc an ctHb. Lact differed significantly in the lower reference limit between the BGAs and CLAs. The simultaneous use of both analyzing systems is thus only advisable for Na, K and Gluc.

Evaluation of two benchtop blood gas analyzers for measurement of electrolyte concentrations in venous blood samples from dogs

OBJECTIVE

To assess agreement between 2 benchtop blood gas analyzers developed by 1 manufacturer (BGA 1 and BGA 2 [a newer model with reduced maintenance requirements]) and a reference chemistry analyzer for measurement of electrolyte (sodium, chloride, and potassium) in blood samples from dogs.

ANIMALS

17 healthy staff- and student-owned dogs and 23 client-owned dogs admitted to an emergency and intensive care service.

PROCEDURES

Blood collected by venipuncture was placed in lithium heparin-containing tubes. Aliquots were analyzed immediately with each BGA. Samples were centrifuged, and plasma was analyzed with the reference analyzer. Results for each BGA were compared with results for the reference analyzer by Passing-Bablok regression analysis. Percentage differences between BGA and reference analyzer results were compared with published guidelines for total allowable error.

RESULTS

Proportional bias was detected for measurement of chloride concentration (slope, 0.7; 95% CI, 0.7 to 0.8), and constant positive bias was detected for measurement of chloride (y-intercept, 34, mmol/L; 95% CI, 16.9 to 38 mmol/L) and potassium (y-intercept, 0.1 mmol/L; 95% CI, 0.1 to 0.2 mmol/L) concentrations with BGA 1. There was no significant bias for measurement of potassium or chloride concentration with BGA 2 or sodium concentration with either BGA. Differences from the reference analyzer result exceeded total allowable error guidelines for ≥ 1 sample/analyte/BGA, but median observed measurement differences between each BGA and the reference analyzer did not.

CONCLUSIONS AND CLINICAL RELEVANCE

Good agreement with reference analyzer results was found for measurement of the selected electrolyte concentrations in canine blood samples with each BGA.

Electrolyte measurements differ between point-of-care and reference analysers in dogs with hypoadrenocorticism

INTRODUCTION

Dogs treated for hypoadrenocorticism are monitored through analysis of their blood electrolytes. This is routinely performed with point-of-care analysers and doses of medications are adjusted based on the results.

OBJECTIVES

To investigate the performance of two point-of-care analysers (IDEXX Catalyst Dx and IDEXX VetStat) against a reference laboratory method for the measurement of blood sodium, potassium and chloride concentrations, as well as sodium: potassium ratios, in dogs diagnosed with and treated for hypoadrenocorticism.

METHODS

Forty-eight dogs were enrolled into a prospective cross-sectional study. Paired blood samples were taken and tested on two point-of-care analysers and at a reference laboratory. Statistical analysis was then performed with Bland-Altman analysis and Passing-Bablok regression. The clinical effects of inaccurate electrolyte analysis were investigated.

RESULTS

In total, 329 samples were tested on the Catalyst analyser, while another 72 samples were tested on the VetStat. Passing-Bablok regression identified both proportional and constant bias for some analytes. There was poor agreement between sodium and chloride concentrations on both analysers. Both analysers tended to give higher results than the reference method for all analytes, except for potassium when measured on the VetStat.

CLINICAL SIGNIFICANCE

There are inherent differences between the electrolyte concentrations measured by these two point-of-care analysers and reference laboratory methods in dogs with hypoadrenocorticism.

A method comparison study of a point-of-care blood gas analyser with a laboratory auto-analyser for the determination of potassium concentrations during hyperkalaemia in patients with kidney disease

Introduction

Hyperkalaemia is a common electrolyte disorder that may cause life-threatening cardiac arrythmias. We aimed to determine the agreement of potassium concentrations between GEM premier 3500 point-of-care blood gas analyser (POC-BGA) and Roche Cobas 6000 c501 auto-analyser in patients with hyperkalaemia.

Methods

A prospective, cross-sectional study of all consecutive adult patients referred to the Renal Unit with a serum potassium concentration ≥ 5.5 mmol/L was performed. A total of 59 paired venous blood samples were included in the final statistical analysis. Passing-Bablok regression and Bland Altman analysis were used to compare the two methods.

Results

The median laboratory auto-analyser potassium concentration was 6.1 (5.9-7.1) mmol/L as compared to the POC-BGA potassium concentration of 5.7 (5.5-6.8) mmol/L with a mean difference of - 0.43 mmol/L and 95% upper and lower limits of agreement of 0.35 mmol/L and - 1.21 mmol/L, respectively. Regression analysis revealed proportional systematic error. Test for linearity did not indicate significant deviation (P = 0.297).

Conclusion

Although regression analysis indicated proportional systematic error, on Bland Altman analysis, the mean difference appeared to remain relatively constant across the potassium range that was evaluated. Therefore, in patients presenting to the emergency department with a clinical suspicion of hyperkalaemia, POC-BGA potassium concentrations may be considered a surrogate for laboratory auto-analyser measurements once clinicians have been cautioned about this difference.

Evaluation of a New Automated Routine Measurement for Serum Adjusted Ionized Calcium (at pH 7.4) in Patients Suspected of Calcium Metabolic Disease

Background

Total calcium is a less accurate test in predicting ionized calcium (Ca2+) in patients suspected of calcium metabolic disease. Nevertheless, total calcium continues to be used as routine measurement instead of adjusted Ca2+ (at pH 7.4). In the current study we evaluate a new multichannel instrument, the ISE Module E1200 for adjusted Ca2+ (at pH 7.4), containing three different ion-selective electrode (ISE) units.

Methods

Serum from 1350 patients was compared to the ABL835 flex and KoneLab. Total calcium was also evaluated on the Dimension Vista 1500 system. Correlations between instruments were assessed by Deming regression and degree of agreement by Cohen’s kappa (κ).

Results

Analytical imprecisions for the three ISE units for adjusted Ca2+ (at pH 7.4) was between 0.36% and 2.52%, and for pH between 0.32% and 3.24%. Results were comparable for each ISE unit (r = 0.797–0.917; all P &lt; 0.0001) and in high-throughput settings (r = 0.871; P &lt; 0.0001). The degree of agreement between instruments was moderate to good (κ  =  0.52–0.77). In contrast, there was a very poor agreement (κ = −0.14) for total calcium with discrepancy in 53.4% of the samples.

Conclusions

The new ISE Module E1200 is comparable with the ABL835 flex and KoneLab 30i and therefore may be used for routine analysis of serum adjusted Ca2+ (at pH 7.4). The measured adjusted Ca2+ (at pH 7.4) was less comparable with very poor agreement to total calcium measured on the Dimension Vista 1500 system.

Comparison of electrolyte and glucose levels measured by a blood gas analyzer and an automated biochemistry analyzer among hospitalized patients

Background

Blood gas analyzers are capable of delivering results on electrolytes and metabolites within a few minutes and facilitate clinical decision‐making. However, whether the results can be used interchangeably with values measured by chemistry analyzers remains controversial.

Blood gas analyzers are capable of delivering results on electrolytes and metabolites within a few minutes and facilitate clinical decision‐making. However, whether the results can be used interchangeably with values measured by chemistry analyzers remains controversial.

Methods

In total, arterial and matched venous blood samples were collected from 200 hospitalized patients. Arterial blood samples were evaluated using a RAPIDPOINT 500 to test electrolyte and glucose levels, then the samples were centrifuged and the same parameters were measured with an AU5800. Venous blood samples were processed and tested in accordance with standard operation procedures. Data were compared by using a paired t test, the agreement between the two analyzers was evaluated by using the Bland‐Altman test, and sensitivity and specificity were calculated.

Results

Paired t tests showed that all parameters tested were significantly different between the two analyzers except chloride. The biases calculated indicated that blood gas analyzers tend to underestimate the parameters, and the linear regression showed a strong correlation between the two analyzers. The sensitivity, specificity and kappa values demonstrated that the diagnostic performance of blood gas analyzers is not satisfactory.

Conclusion

The significant reduction in parameter estimation and diagnostic performance we observed suggested that clinicians should interpret results from blood gas analyzers more cautiously. The reference interval of blood gas analyzers should be adjusted accordingly, given that values are underestimated.

New Test, Old Disease: A Case Series of Diabetic Ketoalkalosis

BACKGROUND

Diabetic ketoalkalosis (DKAlk) was first described in 1967 as a rare complication of diabetic ketoacidosis with normal or elevated pH/bicarbonate and elevated anion gap (AG) from high β-hydroxybutyrate (BHB).

OBJECTIVE

We report a case series of patients with DKAlk to show how venous blood gas (VBG) electrolytes alone may misdiagnose these patients.

METHODS

This was a case series of DKAlk patients with concomitant VBG and basic metabolic panel (BMP) electrolytes who met the following criteria for DKAlk: BMP hyperglycemia (glucose >250 mg/dL), elevated AG (>15 mEq/L), elevated BHB (>1.2 mmol/L), and high Delta (Δ) gap (>6 mEq/L [bicarbonate gap (BG): measured bicarbonate - 24] - [AG - 12]). Data are reported as median with interquartile range (IQR) (25%, 75%) and group comparisons utilized Mann-Whitney U test (two-tailed, α = 0.05).

RESULTS

We found 10 patients with DKAlk in 2 months. Patients ranged in age from 13 to 77 years, 50% were male, and all were African American. Most patients (8 of 10) were vomiting with hyperglycemia (350 to >600 mg/dL). DKAlk BMP AG ranged from 18 to 34 mmol/L and BHB from 1.74 to 9.09 mmol/L. For bicarbonate, we found no significant difference between VBG (24 mmol/L) and BMP (22 mmol/L) (p = 0.796). VBG chloride (98 mmol/L) was significantly higher than BMP chloride (88 mmol/L) (p < 0.005). This falsely elevated VBG chloride resulted in undervaluing of all VBG AGs, missing almost all of the patients with DKAlk.

CONCLUSIONS

We found that DKAlk is more common than previously reported. We recommend screening with BMP electrolytes and BHB levels for hyperglycemic ED patients who are vomiting or suspected of hypovolemia.

Advances in diagnostic microfluidics

Microfluidics is an emerging field in diagnostics that allows for extremely precise fluid control and manipulation, enabling rapid and high-throughput sample processing in integrated micro-scale medical systems. These platforms are well-suited for both standard clinical settings and point-of-care applications. The unique features of microfluidics-based platforms make them attractive for early disease diagnosis and real-time monitoring of the disease and therapeutic efficacy. In this chapter, we will first provide a background on microfluidic fundamentals, microfluidic fabrication technologies, microfluidic reactors, and microfluidic total-analysis-systems. Next, we will move into a discussion on the clinical applications of existing and emerging microfluidic platforms for blood analysis, and for diagnosis and monitoring of cancer and infectious disease. Together, this chapter should elucidate the potential that microfluidic systems have in the development of effective diagnostic technologies through a review of existing technologies and promising directions.

Multilevel qualification of a large set of blood gas analyzers: Which performance goals?

BACKGROUND

Blood gas analyzers are frequently installed as point of care devices and thus allow rapid decision making. Few data are available regarding analytical performance of large sets of BGA. We aimed at evaluating 22 ABL 90 Flex Plus analyzers intended to be deployed. The evaluation was performed at the device level and at the entire set level to characterize the quality of measurements but also to ensure consistency across the devices deployed in the hospital.

METHODS

Imprecision and total error were assessed for pH, pCO2, pO2, sodium, potassium, ionized calcium, glucose, lactate and oximetry parameters. Imprecision at the hospital level including between device variability was also evaluated. One of the two analyzers used in the central laboratory was correlated with a GEM Premier 4000 and a Cobas b221 analyzers. Thereafter, we tested sequentially the 20 instruments intended to be deployed in care service in comparison with the reference device.

RESULTS

Heterogeneity of analytical performance across the different analyzers was low, allowing to consider the whole set as a unique analyzer. The total error was in line with performance goals. Analytical performance of the analyzers was found suitable for use in clinical practice.

CONCLUSIONS

Our study is an example of the qualification of a set of point and underscores 1)The need for a unified qualification scheme when multiple analyzers are deployed simultaneously 2) analytical performance goals compatible with clinical use and the state of the art for all parameters.

Comparison of Total Bilirubin Values Measured with ABL 735 Blood Gas Analyzer and Roche Cobas C8000 Chemistry Analyzer in Age-Segregated Pediatric Patients

Aim: Measurement of blood bilirubin levels is a crucial analysis because of the toxic effects of bilirubin on brain tissue, particularly in preterm neonates. The aim of this study was to investigate the consistency of the total bilirubin values obtained by the blood gas analyzer and the autoanalyzer.

Material and Methods: In this study, we used total bilirubin data of 407 pediatric patients from Kocaeli University Medical Faculty Education and Research Hospital Central Laboratory System. Total bilirubin data, provided that it was measured simultaneously, was obtained from ABL 735 blood gas analyzer and Roche Cobas C8000 chemistry analyzer. Pediatric patients (neonates, infant and children under 17 years old) were selected retrospectively by year between 2015-2017.

Results: Under a cut-off value (14.6 mg/dL) ABL 735 blood gas analyzer and Roche COBAS C8000 chemistry analyzer had strong correlation (r = 0.939) for total bilirubin measurements. It was found that 2-15 days old neonates give more scattered total bilirubin data by Bland Altman analysis in two measurements. Statistical analysis performed to compare whole total bilirubin data identity between two measurements: correlation coefficient was found r = 0.949 a statistically significant positive correlation (p < 0.001).

Conclusion: According to our analysis which was supported by previous studies in the literature, we can say that the compatibility between the blood gas analyzer (multi-wave-length spectrophotometric technique) and the chemistry analyzer becomes weaker when the total bilirubin levels exceed 14.6 mg/dL.

Evaluation of the analytical performances of Cobas 6500 and Sysmex UN series automated urinalysis systems with manual microscopic particle counting

Introduction

Automated urinalysis systems are valuable tools in clinical laboratories, especially those with a high work load. The objective of this study was to compare the analytical performance of Sysmex UN series urine analyser, which may become a new one in our laboratory, with the Cobas 6500 automated urine analyser, which is used in our laboratory for a long time. For comparisons, manual microscopical examination was accepted as reference method.

Materials and methods

A total of 470 urine samples were tested in the two automated urinalysis systems, and urine sediment testing with manual microscopy was applied to a 100 pathological samples of the total 470. The diagnostic performance of the two automated urine analysers was compared with each other and manual microscopy.

Results

Differences were determined between automated and manual microscopy in some pathological samples. The resultant regression equations were as follows. Comparison of Cobas U701 with Sysmex UF-5000: y = - 0.57 (- 0.85 to - 0.29) + 0.95 (0.92 to 0.99) x for RBC, and y = - 0.11 (- 0.54 to 0.29) + 0.89 (0.84 to 0.98) x for WBC; comparison of Cobas U701 with manual microscopy: y = - 0.45 (- 0.85 to 0.21) + 1.00 (0.92 to 1.07) x for WBC; and comparison of Sysmex UF-5000 with manual microscopy: y = - 0.74 (- 1.09 to - 0.57) + 0.87 (0.85 to 0.91) x for WBC.

Conclusions

We can conclude that the new Sysmex UN series urine analyser can be safely used in our laboratory. Although the results showed good to moderate concordance, the microscopy results of the automated platforms should be confirmed by manual microscopy, particularly in pathological samples.

Optical Sensor for Real-Time pH Monitoring in Human Tissue

This article reports on a fiber-based ratiometric optical pH sensor for use in real-time and continuous in vivo pH monitoring in human tissue. Stable hybrid sol-gel-based pH sensing material is deposited on a highly flexible plastic optical fiber tip and integrated with excitation and detection electronics. The sensor is extensively tested in a laboratory environment before it is applied in vivo in a human model. The pH sensor performance in the laboratory environment outperforms the state-of-the-art reported in the current literature. It exhibits the highest sensitivity in the physiological pH range, resolution of 0.0013 pH units, excellent sensor to sensor reproducibility, long-term stability, short response time of <2 min, and drift of 0.003 pH units per 22 h. The sensor also exhibits promising performance in in vitro whole blood samples. In addition, human evaluations conducted under this project demonstrate successful short-term deployment of this sensor in vivo.

Validation of the blood gas analyzer for pH measurements in IVF culture medium: Prevent suboptimal culture conditions

Measurement of pH in IVF-media using the blood gas analyzer (BGA) requires validation, because IVF-media is outside the intended scope of the BGA. To determine whether the Siemens Rapidpoint 500 BGA is suitable for pH measurements in IVF-media this study will validate the BGA and assess its accuracy. In this method comparison study, the pH of over three hundred IVF-media samples was measured with the BGA and a pH electrode (Hanna pH checker). The precision of both the BGA and the pH electrode were excellent (coefficient variation <1.4%). However, the closeness of agreement between measured values of both devices were not equivalent to each other in the tested IVF-media, showing 15% to 85% accordance between devices. The pH measured with the blood gas analyzer was also significantly higher in the tested media, compared to that measured by the pH electrode. One of the tested media did not reach its target pH when it was measured with the BGA, even at 9% CO₂. The results show that the validated blood gas analyzer produces excellent results in terms of precision but not in terms of accuracy. Inaccurate measurement may lead to misinterpretation of results and consequently to suboptimal culture conditions. Therefore, each laboratory is encouraged to perform a validation of their BGA.

Concordance of the ions and GAP anion obtained by gasometry vs standard laboratory in critical care

OBJECTIVE

To evaluate the differences observed in ion and GAP anion determinations obtained by point-of-care (POC) blood gas versus laboratory biochemical testing, and to analyze the possible errors according to the limits of normality.

MATERIAL AND METHODS

A descriptive, cross-sectional retrospective study was made to assess concordance between two diagnostic tests in patients admitted to the Critical Care Unit of Ourense University Hospital Complex (Spain), between July and November 2015, involving at least one coinciding biochemical test and POC determination. Patients under 18years of age were excluded.

RESULTS

A total of 1,073 samples were analyzed. Lin's concordance correlation coefficients for sodium, potassium and chlorine were 0.87, 0.84 and 0.72, respectively. Kappa concordance of the normality limits for sodium, potassium and chlorine was 0.63, 0.74 and 0.32. The results indicated poor correlation of the anion GAP and null concordance between POC and biochemical testing, including the value corrected for albumin.

CONCLUSIONS

Poor concordance was observed between the ion values as determined by biochemistry and blood gases; the two methods are therefore not interchangeable. Kappa agreement with normality limits was good for sodium and potassium, and weak for chlorine. Possible validity was noted in orienting the classification within the ion limits, with the exception of chlorine. No agreement was recorded in relation to the anion GAP, even that corrected for albumin.

Correlation between sodium, potassium, hemoglobin, hematocrit, and glucose values as measured by a laboratory autoanalyzer and a blood gas analyzer

INTRODUCTION

Blood gas analyzers can be alternatives to laboratory autoanalyzers for obtaining test results in just a few minutes. We aimed to find out whether the results from blood gas analyzers are reliable when compared to results of core laboratory autoanalyzers.

MATERIALS AND METHODS

This retrospective, single-centered study examined the electronic records of patients admitted to the emergency department of a tertiary care teaching hospital between May 2014 and December 2017. Excluded from the study were patients under 18 years old, those lacking data, those who had any treatment before the laboratory tests, those whose venous gas results were reported more than 30 minutes after the blood sample was taken and for whom any of the laboratory tests were performed at a different time, and recurrent laboratory results from a single patient.

RESULTS

Laboratory results were analyzed from a total of 31,060 patients. The correlation coefficients for sodium, potassium, hemoglobin, hematocrit, and glucose levels measured by a blood gas analyzer and a laboratory autoanalyzer were 0.725, 0.593, 0.982, 0.958, and 0.984, respectively; however, there were no good, acceptable agreement limits for any of the parameters. In addition, these results did not change according to the different pH stages (acidosis, normal pH and alkalosis).

CONCLUSION

The two types of measurements showed a moderate correlation for sodium and potassium levels and a strong correlation for glucose, hemoglobin, and hematocrit levels, but none of the levels had acceptable agreement limits. Clinicians should be aware of the limitations of blood gas analyzer results.

How closely do blood gas electrolytes and haemoglobin agree with serum values in adult emergency department patients: An observational study

OBJECTIVE

The aims of this study were to establish the bias (mean difference) and 95% limits of agreement (LoA) between electrolyte values (sodium and potassium) and haemoglobin between whole blood analysed by the ED resuscitation room blood gas analyser and specimens analysed using standard techniques in the central hospital laboratory and to determine the proportion of analyses falling outside defined clinically acceptable LoA and pathology expert defined standards.

METHODS

Prospective cohort study. Paired blood gas analyser and laboratory samples taken no more than 10 min apart were included. The primary outcome of interest was bias and 95% LoA by Bland-Altman analysis. Subgroup analyses for values outside the normal range were also conducted.

RESULTS

Three hundred and fifty-two sample pairs were included in the analysis. For sodium concentration the bias was 0.6 mmol/L (95% LoA -3.3 to 4.6 mmol/L). For potassium concentration the bias was 0.21 mmol/L (95% LoA -0.36 to 0.79 mmol/L). For haemoglobin concentration the bias was -1.6 g/dL (95% LoA -10.2 to 6.9 g/dL). For sodium and haemoglobin concentrations, >95% of results fell within the defined clinically acceptable limits. For potassium concentration, >90% of results fell within the defined clinically acceptable limits. In general, serum sodium and potassium concentrations were slightly higher than blood gas levels and for haemoglobin serum levels were slightly lower.

CONCLUSION

Agreement between blood gas analysis and laboratory analysis for sodium, potassium and haemoglobin concentrations shows acceptable agreement for use in time critical clinical decision-making in ED.

Blood Gas Analyzer Accuracy of Glucose Measurements

OBJECTIVE

To investigate the comparability of glucose levels measured with blood gas analyzers (BGAs) and by central laboratories (CLs).

MATERIAL AND METHODS

Glucose measurements obtained between June 1, 2007, and March 1, 2016, at the Vanderbilt University Medical Center were reviewed. The agreement between CL and BGA results were assessed using Bland-Altman, consensus error grid (CEG), and surveillance error grid (SEG) analyses. We further analyzed the BGAs' performance against the US Food and Drug Administration (FDA) 2014 draft guidance and 2016 final guidance for blood glucose monitoring and the International Organization for Standardization (ISO) 15197:2013 standard.

RESULTS

We analyzed 2671 paired glucose measurements, including 50 pairs of hypoglycemic values (1.9%). Bland-Altman analysis yielded a mean bias of -3.1 mg/dL, with 98.1% of paired values meeting the 95% limits of agreement. In the hypoglycemic range, the mean bias was -0.8 mg/dL, with 100% of paired values meeting the 95% limits of agreement. When using CEG analysis, 99.9% of the paired values fell within the no risk zone. Similar results were found using SEG analysis. For the FDA 2014 draft guidance, our data did not meet the target compliance rate. For the FDA 2016 final guidance, our data partially met the target compliance rate. For the ISO standard, our data met the target compliance rate.

CONCLUSION

In this study, the agreement for glucose measurement between common BGAs and CL instruments met the ISO 2013 standard. However, BGA accuracy did not meet the stricter requirements of the FDA 2014 draft guidance or 2016 final guidance. Fortunately, plotting these results on either the CEG or the SEG revealed no results in either the great or extreme clinical risk zones.

Application of Sigma Metrics and Performance Comparison Between Two Biochemistry Analyser and a Blood Gas Analyser for the Determination of Electrolytes

INTRODUCTION

Electrolytes have a narrow range of biological variation and small changes are clinically significant. It is important to select the best method for clinical decision making and patient monitoring in the emergency room. The sigma metrics model provides an objective method to evaluate the performance of a method.

AIM

To calculate sigma metrics for electrolytes measured with one arterial blood gas analyser including two auto-analysers that use different technologies. To identify the best approach for electrolyte monitoring in an emergency setting and the context of routine emergency room workflow.

MATERIALS AND METHODS

The Coefficient of Variation (CV) was determined from Internal Quality Control (IQC). Data was measured from July 2015 to January 2016 for all three analysers. The records of KBUD external quality data (Association of Clinical Biochemists, Istanbul, Turkey) for both Mindray BS-2000M analyser (Mindray, Shenzhen, China) and Architect C16000 (Abbott Diagnostics, Abbott Park, IL) and MLE clinical laboratory evaluation program (Washington, DC, USA) for Radiometer ABL 700 (Radiometer Trading, Copenhagen, Denmark) during the study period were used to determine the bias.

RESULTS

The calculated average sigma values for sodium (-1.1), potassium (3.3), and chloride (0.06) were with the Radiometer ABL700. All calculated sigma values were better than the auto-analysers.

CONCLUSION

The sigma values obtained from all analysers suggest that running more controls and increasing the calibration frequency for electrolytes is necessary for quality assurance.

Plasma sodium measurements by direct ion selective methods in laboratory and point of care may not be clinically interchangeable

An estimated 25 % of indirect ion selective electrode (ISE) ICU plasma sodium measurements differ from corresponding direct ISE values by at least 4 mmol/L, the dominant factor being indirect ISE over-estimation driven by hypoproteinemia. Since direct measurements are considered unaffected by protein concentrations, we investigated whether direct ISE plasma sodium measurements in the laboratory and at point of care in ICU show sufficient agreement to be clinically interchangeable. From a 5 year clinical chemistry database, 9910 ICU plasma samples were assessed for agreement between direct ISE sodium measurements in ICU (ABL 700) and in the central laboratory (Vitros Fusion). The relationship between differences in paired plasma sodium measurements (Vitros-ABL) and total plasma protein concentrations was evaluated by generalized estimating equation linear regression. Patients were hypo-proteinemic [mean (SD) total protein concentration 56.9 (9.04) g/L]. Mean (SD) paired Vitros-ABL sodium measurements was -0.087 (1.74) mmol/L, range -14 to +10 mmol/L. Disagreement at ≥|4|mmol/L, ≥|3|mmol/L and ≥|2|mmol/L was present in 409 (4.1 %), 1333 (13.4 %) and 3591 (36.2 %) pairs respectively. Test-retest disagreement estimates within either source alone were substantially lower. Small negative Vitros-ABL differences associated with low plasma protein concentrations were reversed at high protein concentrations. Disagreement between plasma sodium concentrations monitored by two common direct ISE analyzers was substantially less than reported between direct and indirect ISE devices, although a protein influence of low clinical importance persisted. Disagreement was sufficient to jeopardize safe interchangeable interpretation in situations with a low tolerance for imprecision, such as hyponatremia correction.

Comparison of serum sodium levels measured by blood gas analyzer and biochemistry autoanalyzer in patients with hyponatremia, eunatremia, and hypernatremia

BACKGROUND

Blood gas analyzer (BGA) electrolyte measurements are frequently used in emergency departments (EDs) pending biochemistry laboratory autoanalyzer (BLA) results. There is lack of data in the literature in terms of agreement of these 2 measurement methods of sodium. We aimed to comprehensively evaluate the agreement in hyponatremia, eunatremia, and hypernatremia groups.

METHODS

Retrospectively, adult subjects who presented to ED of a tertiary care teaching hospital and had simultaneous BGA and BLA results were included in the study. Blood pairs were grouped into hyponatremia, eunatremia, and hypernatremia according to BLA results. Agreement of sodium measurements between the methods were evaluated by Bland-Altman plots and Passing and Bablok regression analysis.

RESULTS

A total of 2557 blood pairs (1326 males [51.8%]) were included. Median age of the patients was 66 years (18-103). The numbers of patients with hyponatremia, eunatremia, and hypernatremia were 487 (19%), 1943 (76%), and 127 (5%), respectively. The minimum and maximum serum sodium levels measured by biochemistry analyzer were 106 and 171 mmol/L, respectively. The Pearson linear correlation coefficient between BGA and BLA for sodium measurements were 0.574, 0.358, and 0.562 in hyponatremia, eunatremia, and hypernatremia groups, respectively. The absolute mean difference for the 3 groups was greater than 4 mmol/L. Biochemistry laboratory autoanalyzer tended to measure serum sodium higher than BGA in all sodium groups. Passing and Bablok regression analysis showed significant differences between the 2 methods in all sodium groups.

CONCLUSION

This is the first comprehensive evaluation of agreement between BGA and BLA in distinct sodium groups. Significant differences should be taken into account when these patients are managed in the ED.

How reliable are electrolyte and metabolite results measured by a blood gas analyzer in the ED?

INTRODUCTION

Blood gas analysis is a frequently ordered test in emergency departments for many indications. It is a rapid technique that can analyze electrolyte and metabolites in addition to pH and blood gases. The aim of this study was to investigate the correlation of electrolyte and metabolite results measured by blood gas and core laboratory analyzers.

METHODS

This was a prospective, single-center observational study conducted in a tertiary care center's emergency department. All adult patients requiring arterial/venous blood gas analysis and core laboratory tests together for any purpose were consecutively included in the study between April 2014 and July 2015. Patients younger than 16 years, having any intravenous infusion or blood transfusion prior to sampling, or who were pregnant were excluded.

RESULTS

A total of 1094 patients' (male = 547, female = 547) paired blood samples were analyzed. The mean age was 58.10 ± 21.35 years, and there was no difference between arterial and venous sampling groups by age, pH, or sex (P = .93, .56, and .41, respectively). Correlation coefficients for hemoglobin, hematocrit, glucose, potassium, sodium, and chloride levels measured by blood gas analyzer and core laboratory analyzers were 0.922, 0.896, 0.964, 0.823, 0.854, and 0.791, respectively.

CONCLUSION

Blood gas analysis results were strongly correlated for hemoglobin, hematocrit, glucose, potassium, and sodium levels but were only moderately correlated for chloride levels. These parameters as measured by a blood gas analyzer seem reliable in critical decision making but must be validated by core laboratory results.