Concordance between point-of-care blood gas analysis and laboratory autoanalyzer in measurement of hemoglobin and electrolytes in critically ill patients

[Comparison of a portable hemoglobinometer (Verio Q Red) with clinical laboratory results in routine clinical practice]

OBJECTIVE

To analyze the concordance between a hemoglobinometer with capillary blood sample and the clinical laboratory with a venous blood sample.

DESIGN

Cross-sectional concordance study.

LOCATION

Care Centre Primary Bufalà-Canyet Primary and Care Centre Primary Dalt la Vila Primary Care Center, Badalona, Barcelona.

PARTICIPANTS

Random selection of participants who attended routine blood tests. Over 18years old. No abandonment or loss was obtained.

MAIN INTERVENTIONS AND MEASUREMENTS

Sex, age, and reason for the blood test were collected from the medical history. Venous blood is drawn, and simultaneously, capillary blood is collected.

RESULTS

120 individuals are included, with an average age of 58.9years. The Bland-Almant graph showed differences within the confidence intervals for hemoglobin and hematocrit. The mean differences between the values of the Verio Q Red hemoglobinometer and those of the clinical laboratory were -0.42mg/dl for hemoglobin and -1.25% for hematocrit. The intraclass correlation coefficient showed excellent correlation for hemoglobin and hematocrit between the Verio Q Red hemoglobinometer and the clinical laboratory. Pearson's correlation for hemoglobin was 0.737 and for hematocrit 0.787.

CONCLUSIONS

The Verio Q hemoglobinometer is a valid tool for the early diagnosis of anemias and can be very useful in primary care consultations.

A Retrospective Database Analysis to Investigate if Electrolytes in Venous Blood are Equivalent to the Levels in Arterial Blood

Background

In a critically ill patient, when an arterial blood sample is processed on an arterial blood gas (ABG) analyzer, it also measures electrolytes apart from analyzing the blood gases. The turnaround time for ABG analysis is way too less compared to the conventional electrolyte analysis with a serum sample.

Objective

This study intends to investigate whether values of electrolytes estimated in arterial blood can substitute the routinely practiced method.

Materials and methods

This is a retrospective cross-sectional study. The source of data is patients' reports of serum electrolytes and ABG analysis from the Clinical Biochemistry laboratory, CIMS Teaching Hospital, Chamarajanagar between January and June 2021. The electrolytes report of 200 patients from whom both arterial and venous blood samples were sent to the Clinical Biochemistry laboratory on the same day and at the same time for analysis were selected. The data was compiled, compared, and correlated using a suitable statistical tool.

Results

The mean and standard deviation of sodium (135.62 ± 5.20 in venous vs 134.08 ± 8.49 in arterial blood), potassium (4.20 ± 0.64 vs 3.80 ± 0.75), and chloride (102.28 ± 4.99 vs 96.33 ± 8.11) were observed. However, when the concordance correlation coefficient and Bland-Altman plot analysis were made there was no agreement between electrolytes analyzed on serum in an autoanalyzer with that of ABG analyzer.

Conclusion

We conclude that the electrolytes measured by a conventional autoanalyzer on a serum sample cannot be replaced by values analyzed on a blood gas analyzer.

How to cite this article

Devaki RN, Kasargod P, Roopa Urs AN, Chandrika N. A Retrospective Database Analysis to Investigate if Electrolytes in Venous Blood are Equivalent to the Levels in Arterial Blood. Indian J Crit Care Med 2024;28(5):442-446.

Blood glucose monitoring in critically ill adult patients: type of sample and method of analysis. Systematic review and meta-analysis

INTRODUCTION

The clinical guideline for the management of sepsis, recommends using arterial blood samples for glycaemic control. A multicentre study in 86 Spanish intensive care units (ICU) revealed that 85.4% of ICUs used capillary puncture.

OBJECTIVE

To analyse the reliability of glycaemia by comparing different blood samples (arterial, venous, capillary) and instruments (glucometers, gasometers, central laboratory). Secondarily, to estimate the effect of confounding variables and the performance of measuring instruments as determined by different quality standards.

METHODOLOGY

Systematic review and meta-analysis with search in PubMed, CINAHL and Embase databases in September-2021 and September-2022, with no time or language limits. Grey literature sources: DART-Europe, OpenGrey and Google Scholar. Results summarised by qualitative (description of results, study characteristics) and quantitative (meta-analysis to assess standardised mean difference) synthesis. Methodological quality of articles assessed with Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2).

PROTOCOL

https://osf.io/ DOI 10.17605/OSF.IO/T8KYP.

RESULTS

A total of 32 articles and 5451 patients were included. No discrepancies were obtained between arterial glucometer vs laboratory samples [bias (95%CI): 0.01 (-0.12 to 0.14) mg/dL]. In contrast, arterial samples with a gasometer did significantly overestimate [bias (95%CI): 0.12 (0.01 to 0.24) mg/dL]. The same trend is seen in capillaries with a glucometer, although not significantly [bias (95%CI): 0.07 (--0.02 to 0.15) mg/dL]. There is discrepancy between studies on the effect of haematocrit and acid-base balance. The greatest consensus is on the poor agreement of glucometer with capillary vs laboratory samples in the presence of shock and vasopressor support, renal failure or during vitamin C treatment.

CONCLUSIONS

The evidence to date recommends the use of arterial blood with a blood glucose meter for better reliability of glycaemic analysis and less effect of possible confounding variables, frequently present in the critically ill adult patient.

Maximizing Microsampling: Measurement of Comprehensive Metabolic and Lipid Panels Using a Novel Capillary Blood Collection Device

BACKGROUND

Demand continues to grow for patient-centric sampling solutions that enable collection of small volumes of blood outside of healthcare facilities. Various technologies have been developed to facilitate sample collection but gaps in knowledge remain, preventing these technologies from replacing standard venipuncture.

METHODS

A novel blood collection device, Touch Activated Phlebotomy (TAP) II® from YourBio Health, and standard fingerstick collection using a BD Microtainer® were utilized to collect capillary serum samples. Measurements of a comprehensive metabolic and lipid panels were measured on these samples and compared to results from venous serum samples that were collected in parallel. Hemolysis was used to assess sample quality. Sample volumes obtained from self-collected TAP II samples were also determined.

RESULTS

Correlation of capillary serum with respect to venous serum was demonstrated (R > 0.9) for professionally collected TAP II samples, self-collected TAP II samples, and professionally collected fingerstick samples for alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, cholesterol, high-density lipoprotein, total bilirubin, and triglycerides. Results for creatinine demonstrated acceptable correlation, however, a consistent negative bias was observed. Biases (with unacceptable correlations) were also observed for measurements of carbon dioxide and potassium. Correlative results for albumin were not consistently acceptable across the collection techniques utilized while the remaining analytes tested did not demonstrate acceptable correlations under any condition. Correlation results, however, would improve with a wider distribution of analyte concentrations.

CONCLUSIONS

Collections of small volumes of liquid blood continue to show potential as a patient-centric solution.

Implications of differences between point-of-care blood gas analyser and laboratory analyser potassium results on hyperkalaemia diagnosis & treatment

BACKGROUND

Hyperkalaemia is managed in the emergency department (ED) following measurement of potassium results by blood gas analysers (BGA) or laboratory analysers (LAB).

AIMS

To determine the prevalence of clinically significant differences between BGA and LAB potassium results and the impact on ED hyperkalaemia management.

METHODS

Retrospective analysis of time-matched ED BGA and LAB potassium samples from 2019 to 2020 (taken within 15 min, one or both results ≥6.0 mmol/L). Mean differences and 95% limits of agreement (LoA) were determined for pairs with one or both results ≥6.0 mmol/L and a separate 500 consecutive sample pairs.

RESULTS

Four hundred eighty-eight matched BGA and LAB samples met the inclusion criteria. Of these, 201 (41.2%) differed by ≤0.5 mmol/L, 169 (34.6%) included a haemolysed LAB sample, and 12 (2.5%) had an unreportable BGA sample. One hundred six (21.7%) pairs differed by >0.5 mmol/L, and 60/106 (57%) had normal LAB potassium results, but BGA indicated moderate/severe hyperkalaemia (two of these pairs received hyperkalaemia treatment). Of patients with a haemolysed LAB sample, or where pairs differed by >0.5 mmol, 48 were treated with insulin and five (10.4%) experienced hypoglycaemia. Mean differences and LoA for pairs with LAB results <6.0 mmol/L but BGA ≥6.0 mmol/L demonstrated unacceptable agreement, with 18 (25.7%) BGA results exceeding 8.0 mmol/L.

CONCLUSIONS

Potentially significant discordance may occur between BGA and LAB potassium results. Clinicians need to be aware of factors impacting both analytical methods' accuracy (such as poor venepuncture or sample handling, (K) EDTA interference) and undetectable haemolysis with BGA measurements. We recommend BGA hyperkalaemia be confirmed with LAB results using a non-haemolysed sample where time permits.

Compatibility levels between blood gas analysis and central laboratory hemoglobin and electrolyte tests in pediatric patients: A single-center experience

INTRODUCTION

We aimed to evaluate the interchangeability of sodium, potassium, hemoglobin, and hematocrit measurement between the blood gas analyzers and laboratory automatic analyzers results.

METHODS

This was a retrospective cross-sectional study. The results of 1927 paired samples analyzed simultaneously with the blood gas analyzer and the laboratory automatic analyzer were compared. The Bland-Altman and Cohen's kappa statistic detected the agreement between the two analyses.

RESULTS

The limits of agreement (±1.96 standard deviation of the mean difference) were -11.1 to 20.3 for sodium, -1.9 to 0.5 for potassium, -16.1 to 12.9 for hematocrit, and -5.0 to 4.0 for hemoglobin. Agreement between the two analyses was not acceptable within the defined clinically acceptable limits. In addition, none of the kappa values were higher than 0.60, which highlights the lack of agreement between the two analyzers.

CONCLUSION

The blood gas analyzers and laboratory automatic analyzers results cannot be used interchangeably.

Agreement of Potassium, Sodium, Glucose, and Hemoglobin Measured by Blood Gas Analyzer With Dry Chemistry Analyzer and Complete Blood Count Analyzer: A Two-Center Retrospective Analysis

Background

Blood gas analyzers (BGAs) and dry biochemistry analyzers for potassium and sodium are based on direct electrode methods, and both involve glucose oxidase for glucose detection. However, data are lacking regarding whether the results of the two assay systems can be used interchangeably. In addition, there remains controversy over the consistency between BGA-measured hemoglobin and complete blood count analyzer data. Here, we compared the consistency of sodium, potassium, glucose, and hemoglobin levels measured by BGA and dry chemistry and complete blood count analyzers.

Methods

Data from two teaching hospitals, the Zhejiang Provincial People's Hospital (ZRY) and the Qianfoshan Hospital (QY), were retrospectively analyzed based on dry biochemistry and complete blood count analyzer results as the reference system (X) and BGA as the experimental system (Y). Plasma was used for biochemical analysis at the ZRY Hospital, and serum at the QY Hospital. Paired data from the respective hospitals were evaluated for consistency, and biases between methods were assessed by simple correlation, Passing–Bablok regression, and Bland–Altman analyses.

Results

The correlations of potassium, sodium, glucose, and hemoglobin measured by BGA and dry biochemistry and complete blood count analyzers were high, at 0.9573, 0.8898, 0.9849, and 0.9883 for the ZRY Hospital and 0.9198, 0.8591, 0.9764, and 0.8666, respectively, for the QY Hospital. The results of Passing to Bablok regression analysis showed that the predicted biases at each medical decision level were within clinically acceptable levels for potassium, sodium, glucose, and hemoglobin at the ZRY Hospital. Only the predicted bias of glucose was below the clinically acceptable medical decision levels at the QY Hospital, while potassium, sodium, and hemoglobin were not. Compared with the reference system, the mean bias for BGA measurements at the ZRY Hospital was −0.08 mmol/L (95% confidence interval [CI] −0.091 to −0.069) for potassium, 1.2 mmol/L (95% CI 1.06 to 1.42) for sodium, 0.20 mmol/L (95% CI 0.167 to 0.228) for glucose, and −2.8 g/L for hemoglobin (95% CI −3.14 to −2.49). The mean bias for potassium, sodium, glucose, and hemoglobin at the QY Hospital were −0.46 mmol/L (95% CI −0.475 to −0.452), 3.7 mmol/L (95% CI 3.57 to 3.85), −0.36 mmol/L (95% CI −0.433 to −0.291), and −8.7 g/L (95% CI −9.40 to −8.05), respectively.

Conclusion

BGA can be used interchangeably with plasma electrolyte results from dry biochemistry analyzers but does not show sufficient consistency with serum electrolyte results from dry biochemistry analyzers to allow data interchangeability. Good consistency was observed between BGA and plasma or serum glucose results from dry biochemistry analyzers. However, BGA-measured hemoglobin and hematocrit assay results should be treated with caution.

Accuracy of Potassium Measurement Using Blood Gas Analyzer

Introduction: Newer blood gas analyzers can measure both blood gases and electrolytes in both arterial and venous blood samples. They are small, compact, and mobile point of care test (POCT) devices. They can produce results in as short as five minutes. We aimed at assessing the accuracy of potassium (K) level measured by gas analyzer (index test) by comparing that to the regular laboratory machine (reference standard) in our hospital. Our goal is to use POCT result of potassium so we may start insulin infusion within five to 10 minutes of arrival of diabetic ketoacidosis (DKA) patients to the emergency room (ER). It takes an average of 30 minutes to get the result using the reference standard machine. Potassium level is needed urgently in cases of DKA before initiating insulin infusion. That is true also during cardiopulmonary resuscitation (CPR) and while replacing K in severe hypokalemia and during the management of hyperkalemia.

Methods: We looked into the potassium results from 265 patients who had venous blood gas (VBG) or arterial blood gas (ABG) samples and compared that to results of potassium in venous blood samples of these same patients done simultaneously or within two hours. All patients who had blood gas and venous blood drawn simultaneously or within two hours were eligible irrespective of gender, age, diagnosis, and location in the hospital. Data were collected between January 2019 and June 2019. We excluded all cases that were receiving IV fluids, diuretics, or potassium supplements. Samples examined were from all different areas of the hospital including emergency room (ER), intensive care unit (ICU), and general floors. All ages and all diagnoses were included.

Results: We used the Bland-Altman method to analyze our data. More than 95% of the data fell within ± 2 standard deviations (S) of the mean difference strongly suggestive of agreement between the index test and the standard reference of the laboratory methods. The bias was 0.19. Lin’s concordance correlation coefficient was 0.6584.

Conclusion: Findings of this study support the use of POCT blood gas analyzer for measuring potassium when the results are needed urgently. When measuring potassium, blood gas analyzers are as accurate as automated analyzers. They produce results in five minutes or so and can be relied upon when potassium level is needed urgently. They are cost-effective and may be available at the bedside.

The effect of heparin concentration on results of venous blood gas of patients admitted to cardiac intensive care unit: A double-blind clinical trial

Background

The aim of the present study was to investigate the effect of heparin (1000 IU/mL) in the blood sample on the results of venous blood gases of patients admitted to the cardiac intensive care unit.

Materials and methods

The present double-blind randomized clinical trial study was performed on 282 samples from 141 patients admitted to the cardiac intensive care unit. Insulin syringes with heparin (1000 IU/mL) and heparin (5000 IU/mL) and 1 cc of blood sample were taken from the peripheral vein, then distributed in two syringes and given to the analyzer.

Results

In the present study, the mean age of the samples was 49.96 ± 9.58. There was a statistically significant difference between the two groups in terms of values of partial pressure of carbon dioxide (PCO2) (P < 0.001), partial pressure of oxygen (PaO2) (P < 0.001), blood oxygen saturation (P < 0.001), bicarbonate ion (P < 0.001), excess base (P < 0.001), hemoglobin (P < 0.001), calcium (P < 0.001), potassium (P < 0.001), and sodium (P < 0.001) in the two groups.

Conclusion

Overall, heparin (1000 IU/mL) led to a less disruption in the results of venous blood gases, and since it has not significantly increased the risk of clots, it is recommended to be used for venous blood gas sampling.

Improving the accuracy of chloride measurements through participation in regular external quality assessment programme

BACKGROUND

A chloride test is an integral part of a basic metabolic panel that is essential for the assessment of a patient's acid-base and electrolyte status. While many methods are available commercially for the routine measurement of chloride, there is a need to address the accuracy and variability among the measurement results, especially with the prevalence of patients seeking treatment across different healthcare providers for alternative opinions.

METHOD

A method based on sector field inductively coupled plasma isotope dilution mass spectrometry (SF-ICP-IDMS) was developed for the measurement of chloride in human serum. The SF-ICP-IDMS method was then used to assign the target values in the Health Sciences Authority (HSA) External Quality Assessment (EQA) Programme to evaluate the results of chloride test from participating clinical laboratories.

RESULTS

The accuracy of the measurements was evaluated by comparing the results with the certified values of Electrolytes in Frozen Human Serum Certified Reference Materials (SRM 956c and SRM 956d) from the National Institute of Standards and Technology (NIST) at different chloride concentration levels. Over a five-year period from 2014-2018, the number of clinical laboratories which participated in the EQA Programme increased from 23 to 33. Comparison of robust means from the laboratories' results with our assigned target values revealed a reduction in relative deviation over time. The relationship between the deviation of each brand of clinical analysers and the chloride levels was established, where a larger deviation was uncovered at low chloride concentration. The SF-ICP-IDMS method was further demonstrated to be comparable with methods used by other metrology institutes in an international comparison organised by HSA under the auspice of the Consultative Committee for Amount of Substance - Metrology in Chemistry and Biology (CCQM).

CONCLUSION

The use of metrologically traceable assigned target values enabled the study of method biasness from a small pool of dataset in each of the four brands of clinical analysers in HSA EQA Programme. This work underscores the need to improve the accuracy of chloride measurements by regular participation in an accuracy-based EQA Programme.

Point of Care Testing of Serum Electrolytes and Lactate in Sick Children

OBJECTIVE

To evaluate the electrolyte and lactate abnormalities in hospitalized children using a point of care testing (POCT) device and assess the agreement on the electrolyte abnormalities between POCT and central laboratory analyzer with venous blood.

METHODS

This observational study recruited hospitalized children aged 1 month to 12 years within two hours of admission. A paired venous sample and heparinized blood sample were drawn and analyzed by the central laboratory and POCT device (Stat Profile Prime Plus-Nova Biomedical, Waltham, MA, USA) for sodium and potassium. Lactate was measured on the POCT device only. The clinical and outcome parameters of children with electrolyte abnormalities or elevated lactate (>2mmol/L), and the agreement between POCT values and central laboratory values were assessed.

RESULTS

A total of 158 children with median (IQR) age 11 (6-10) months and PRISM score 5 (2-9) were enrolled. The proportion of children with abnormal sodium and potassium levels, and acidosis on POCT were 87 (55.1%), 47 (29.7%) and 73 (46.2%), respectively. The interclass coefficient between POCT and laboratory values of sodium and potassium values was 0.74 and 0.71 respectively; P<0.001. Children with hyperlactatemia (81, 51.3%) had higher odds of shock (OR 4.58, 95% CI: 1.6-12.9), mechanical ventilation (OR 2.7, 95% CI 1.1-6.6, P=0.02) and death (OR 3.1, 95% CI 1.3-7.5 P=0.01) compared to those with normal lactate.

CONCLUSION

POCT can be used as an adjunct for rapid assessment of biochemical parameters in sick children. Lactate measured by POCT was a good prognostic indicator.

Intra-patient potassium variability after hypothermic cardiac arrest: a multicentre, prospective study

Background

To date, the decision to set up therapeutic extra-corporeal life support (ECLS) in hypothermia-related cardiac arrest is based on the potassium value only. However, no information is available about how the analysis should be performed. Our goal was to compare intra-individual variation in serum potassium values depending on the sampling site and analytical technique in hypothermia-related cardiac arrests.

Methods

Adult patients with suspected hypothermia-related refractory cardiac arrest, admitted to three hospitals with ECLS facilities were included. Blood samples were obtained from the femoral vein, a peripheral vein and the femoral artery. Serum potassium was analysed using blood gas (BGA) and clinical laboratory analysis (CL).

Results

Of the 15 consecutive patients included, 12 met the principal criteria, and 5 (33%) survived. The difference in average potassium values between sites or analytical method used was ≤1 mmol/L. The agreement between potassium values according to the three different sampling sites was poor. The ranges of the differences in potassium using BGA measurement were − 1.6 to + 1.7 mmol/L; − 1.18 to + 2.7 mmol/L and − 0.87 to + 2 mmol/L when comparing respectively central venous and peripheral venous, central venous and arterial, and peripheral venous and arterial potassium.

Conclusions

We found important and clinically relevant variability in potassium values between sampling sites. Clinical decisions should not rely on one biological indicator. However, according to our results, the site of lowest potassium, and therefore the preferred site for a single potassium sampling is central venous blood. The use of multivariable prediction tools may help to mitigate the risks inherent in the limits of potassium measurement.

Trial registration

ClinicalTrials.gov Identifier: NCT03096561.

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.

Concordance between point-of-care blood gas analysis and laboratory autoanalyzer in measurement of hemoglobin and electrolytes in critically ill patients

BACKGROUND

We tested the hypothesis that the results of the same test performed on point-of-care blood gas analysis (BGA) machine and automatic analyzer (AA) machine in central laboratory have high degree of concordance in critical care patients and that the two test methods could be used interchangeably.

METHODS

We analyzed 9398 matched pairs of BGA and AA results, obtained from 1765 patients. Concentration pairs of the following analytes were assessed: hemoglobin, glucose, sodium, potassium, chloride, and bicarbonate. We determined the agreement using concordance correlation coefficient (CCC) and Bland-Altman analysis. The difference in results was also assessed against the United States Clinical Laboratory Improvement Amendments (US-CLIA) 88 rules. The test results were considered to be interchangeable if they were within the US-CLIA variability criteria and would not alter the clinical management when compared to each other.

RESULTS

The median time interval between sampling for BGA and AA in each result pair was 5 minutes. The CCC values ranged from 0.89(95% CI 0.89-0.90) for chloride to 0.98(95% CI 0.98-0.99) for hemoglobin. The largest bias was for hemoglobin. The limits of agreement relative to bias were largest for sodium, with 3.4% of readings outside the US-CLIA variation rule. The number of readings outside the US-CLIA acceptable variation was highest for glucose (7.1%) followed by hemoglobin (5.9%) and chloride (5.2%).

CONCLUSION

We conclude that there is moderate to substantial concordance between AA and BGA machines on tests performed in critically ill patients. However, the two tests methods cannot be used interchangeably, except for potassium.