Pseudohyperkalemia: A new twist on an old phenomenon

Disorders of potassium homeostasis after kidney transplantation

Disturbances of potassium balance are often encountered when managing kidney transplant recipients (KTR). Both hyperkalemia and hypokalemia may present either as medical emergencies or chronic outpatient abnormalities. Despite the high incidence of hyperkalemia and its potential life-threatening implications, consensus on its management in KTR is lacking. Hypokalemia in KTR is also well-described, although it is given less attention by clinicians compared to hyperkalemia. This article discusses the etiology, pathophysiology and management of both types of potassium disorders in KTR. Once any emergent situation has been corrected, treatment approaches include correcting insulin deficiency if present, adjusting non-immunosuppressive and immunosuppressive medications, eliminating or supplementing potassium as needed, and dietary counselling. Although commonly of multifactorial etiology, ascertaining the specific cause in a particular patient will help guide successful management. Monitoring KTR through regular laboratory testing is essential to detect serious disturbances in potassium balance since patients are often asymptomatic.

Pseudohyperkalemia in pediatric patients with newly diagnosed hematological malignancies

Patients with newly diagnosed hematological malignancies often present with a considerable cellular burden, leading to complications including hyperkalemia. However, pseudohyperkalemia, arising from in vitro cell lysis, can pose challenges in clinical practice. Although pseudohyperkalemia is frequently reported in adult hematological malignancies, its occurrence in pediatric patients is underreported, and its incidence in this demographic remains unclear. We retrospectively reviewed the medical records of pediatric patients who received a new diagnosis of hematological malignancies from 2011 to 2022 at Taichung Veterans General Hospital. Hyperkalemia was defined by a serum or plasma potassium level exceeding 5.5 mEq/L. Pseudohyperkalemia was defined by 1) a potassium decrease of over 1 mEq/L in within 4 h without intervention or 2) the absence of electrocardiography changes indicative of hyperkalemia. Cases with apparent red blood cell hemolysis were excluded. A total of 157 pediatric patients with a new diagnosis of hematological malignancies were included, 14 of whom exhibited hyperkalemia. Among these 14 cases, 7 cases (4.5%) were of pseudohyperkalemia. This rate increased to 21.2% in patients with initial hyperleukocytosis. Pseudohyperkalemia was associated with a higher initial white blood cell count and lower serum sodium level. All episodes of pseudohyperkalemia occurred in the pediatric emergency department, where samples were obtained as plasma, whereas all true hyperkalemia cases were observed in the ordinary ward or intensive care unit, where samples were obtained as serum. Timely recognition of pseudohyperkalemia is crucial to avoiding unnecessary potassium-lowering interventions in pediatric patients with newly diagnosed hematological malignancies.

Artificial intelligence-based model for automatic real-time and noninvasive estimation of blood potassium levels in pediatric patients

Background

An abnormal variation in blood electrolytes, such as potassium, contributes to mortality in children admitted to intensive care units. Continuous and real-time monitoring of potassium serum levels can prevent fatal arrhythmias, but this is not currently practical. The study aims to use machine learning to estimate blood potassium levels with accuracy in real time noninvasively.

Methods

Hospitalized patients in the Pediatric Department of the Rajaie Cardiology and Medical Research Center and Tehran Heart Center were recruited from December 2021 to June 2022. The electrocardiographic (ECG) features of patients were evaluated. We defined 16 features for each signal and extracted them automatically. The dimension reduction operation was performed with the assistance of the correlation matrix. Linear regression, polynomials, decision trees, random forests, and support vector machine algorithms have been used to find the relationship between characteristics and serum potassium levels. Finally, we used a scatter plot and mean square error (MSE) to display the results.

Results

Of 463 patients (mean age: 8 ± 1 year; 56% boys) hospitalized, 428 patients met the inclusion criteria, with 35 patients having a high noise of ECG were excluded. After the dimension reduction step, 11 features were selected from each cardiac signal. The random forest regression algorithm showed the best performance with an MSE of 0.3.

Conclusion

The accurate estimation of serum potassium levels based on ECG signals is possible using machine learning algorithms. This can be potentially useful in predicting serum potassium levels in specific clinical scenarios.

Stability of potassium, calcium and phosphorus electrolytes in three different tubes in patients with essential thrombocytosis

Proper blood collection and timely analysis are vital steps for reliable results. This study aims to compare potassium(K), calcium(Ca), and phosphorus(P) concentrations in serum separator tube (SST), lithium heparin tube without gel (LiH), and lithium heparin tube with a barrier (Barricor)tubes in essential thrombocytosis(ET) patients. Additionally, we assessed short-term stability of these analytes at room temperature. K, Ca and P concentrations of blood taken from 40 ET patients into SST, LiH and Barricor tubes were measured at 0, 2, 4 and 8 h. We calculated the percentage difference and defined the maximum permissible difference (MPD) using the Biological Variation Database. Intertube comparisons were conducted using Passing-Bablok regression and Bland-Altman analysis. Comparing SST to LiH, the percentage difference values for all tests exceeded the MPD. When comparing Barricor to LiH, K and Ca tests were above MPD, except for P. At the 8th hour, LiH showed clinically significant changes in all three electrolytes. Barricor exhibited stability for K, Ca, and P for up to 8 h, with only Ca levels borderline higher than the MPD. Our study reveals clinically significant alterations in K, Ca, and P concentrations in SST compared to LiH tubes, and in K and Ca concentrations in Barricor compared to LiH tubes. While K, Ca and P concentrations were stable for up to 4 h at room temperature in all tube types tested, significant changes were observed in all electrolytes at 8 h in the LiH tube.

Pseudohyperkalemia in chronic lymphocytic leukemia: Prevalence, impact, and management challenges

The term pseudohyperkalemia refers to a false elevation in serum potassium levels due to potassium release from cells in vitro. Falsely elevated potassium levels have been reported in patients with thrombocytosis, leukocytosis, and hematologic malignancies. This phenomenon has been particularly described in chronic lymphocytic leukemia (CLL). Leukocyte fragility, extremely high leukocyte counts, mechanical stress, higher cell membrane permeability related to an interaction with lithium heparin in plasma blood samples, and metabolite depletion due to a high leukocyte burden have been reported to contribute to pseudohyperkalemia in CLL. The prevalence of pseudohyperkalemia is up to 40%, particularly in the presence of a high leukocyte count (>50 × 109/L). The diagnosis of pseudohyperkalemia is often overlooked, which may result in unnecessary and potentially harmful treatment. The use of whole blood testing and point-of-care blood gas analysis, along with thorough clinical evaluation, may help differentiate between true and pseudohyperkalemic episodes.

Hyperkalemia in the setting of severe leukocytosis: Should you treat?

BACKGROUND

Severe hyperkalemia is a common and life-threatening problem presenting to the emergency department. Rapid correction of the electrolyte abnormality is essential but doing so can be detrimental in circumstances under which delaying treatment for confirmation is required. Our case exemplifies one of those scenarios: pseudohyperkalemia in the setting of severe leukocytosis.

CASE

An elderly woman with long-standing but untreated chronic lymphocytic leukemia presented with a left hip fracture. She was found to have a potassium level of 8.4 mEq/L without symptoms of hyperkalemia, renal disease, or EKG findings. Her white blood cell count was 444 K/uL. Despite a potentially life-threatening hyperkalemia, correction was deferred pending confirmation by venous whole blood, which revealed a normal potassium level.

DISCUSSION

Pseudohyperkalemia can occur in the setting of severe leukocytosis. It is important for emergency physicians to recognize this phenomenon and avoid iatrogenic hypokalemia. The pathophysiology behind this phenomenon and the methods for correct analysis are presented here.

Acute hyperkalemia in adults

Hyperkalemia is a common, life-threatening medical situation in chronic renal disease patients in the emergency department (ED). Since hyperkalemia does not present with any specific symptom, it is difficult to diagnose clinically. Hyperkalemia causes broad and dramatic medical presentations including cardiac arrhythmia and sudden death. Hyperkalemia is generally determined through serum measurement in the laboratory. Treatment includes precautions to stabilize cardiac membranes, shift potassium from the extracellular to the intracellular, and increase potassium excretion. The present article discusses the management of hyperkalemia in the ED in the light of current evidence.

Hyperkalemia in Diabetes Mellitus Setting

Diabetes mellitus is a global health problem that affects 9.3% of the worldwide population and is associated with a series of comorbidities such as heart failure (HF) and chronic kidney disease (CKD). Diabetic patients, especially those with associated CKD, are more susceptible to present potassium disorders, in particular hyperkalemia due to kidney disease progression or use of renin-angiotensin-aldosterone blockers. Hyperkalemia is a potentially life-threatening condition that increases the risk of cardiac arrhythmia episodes and sudden death, making the management of potassium levels a challenge to reduce the mortality rate in this population. This review aims to briefly present the potassium physiology and discuss the main conditions that lead to hyperkalemia in diabetic individuals, the main signs, symptoms, and exams for the diagnosis of hyperkalemia, and the steps that should be followed to manage patients with this potentially life-threatening condition.

Pseudohyperkalemia in a Patient With Chronic Lymphocytic Leukemia

Hyperkalemia is a common electrolyte disorder with potentially life-threatening consequences, including cardiac dysrhythmias. Pseudohyperkalemia must always be ruled out before implementing treatment for true hyperkalemia. Here, we present a case of a 63-year-old male with chronic lymphocytic leukemia (CLL) with a white blood cell count greater than 200 thousand/mm³ and persistently high serum potassium concentration as high as 8.4 mmol/L. A venous blood gas analysis was performed, which confirmed the patient's plasma potassium levels were within the normal range (3.7-4.4 mmol/L). In patients with CLL, due to the increased fragility of their white blood cells, mechanical stress such as centrifugation can lead to cell lysis resulting in pseudohyperkalemia. Our emphasis with clinicians is to familiarize themselves with these spurious laboratory values and prevent unnecessary invasive testing and treatment.

Case Report: Familial Pseudohyperkalemia Due to Red Blood Cell Membrane Leak in a Chinese Patient

Hyperkalemia is a critical condition requiring careful evaluation and timely intervention. Many conditions could manifest as pseudohyperkalemia and it's important to differentiate them as inappropriate potassium-lowering therapy might lead to detrimental outcomes. A 56-year-old female was admitted for hyperkalemia (5.62–8.55 mmol/L). She had no symptoms or signs of hyperkalemia. A comprehensive work-up of hyperkalemia retrieved no valuable findings. Her blood samples underwent incubation tests at different temperatures and revealed temperature-dependent potassium leaks from red blood cells. Based on all test results, a diagnosis of hyperkalemia caused by red blood cell membrane defects was suspected. Whole-genome sequencing revealed a heterozygous c.1123C>T (p. R375W) mutation in the ABCB6 gene and confirmed the diagnosis of familial pseudohyperkalemia (FP). FP is an inherited benign condition in which red blood cells have increased cold-induced permeability to potassium. The patient was discharged with no additional treatment and she was suggested avoiding blood donation.

Pseudohyperkalemia accompanying actual hyperphosphatemia and hypocalcemia in an adolescent with T-lymphoblastic lymphoma

Tumor lysis syndrome (TLS) is a life-threatening condition that may occur in patients with lymphoma, leukemia, or cancers with high cellular burdens. Without appropriate treatment, electrolyte imbalances, namely hyperkalemia, hyperphosphatemia, and hypocalcemia, can be fatal in patients with TLS. In pseudohyperkalemia, concurrent hyperphosphatemia and hypocalcemia can render devising a treatment strategy challenging. We report an adolescent with T-lymphoblastic lymphoma who presented with pseudohyperkalemia but actual hyperphosphatemia and hypocalcemia, to highlight the importance of accurate clinical interpretations of laboratory data in patients with TLS.

Effects of handling and storage on potassium concentration in plasma and serum samples obtained from cats

OBJECTIVE

To compare potassium concentrations in feline plasma and serum samples analyzed promptly after collection or after 20 to 28 hours of refrigerated storage.

ANIMALS

41 cats.

PROCEDURES

A venous blood sample was obtained from each cat. Aliquots were placed in 2 tubes without anticoagulant (blood was allowed to clot to derive serum) and 2 tubes with heparin (to derive plasma). One serum and 1 plasma sample were kept at room temperature and analyzed within 60 minutes after collection (baseline); the other serum and plasma samples were analyzed after 20 to 28 hours of refrigerated storage. At both time points, serum and plasma potassium concentrations were measured.

RESULTS

Median baseline serum potassium concentration (4.3 mmol/L) was significantly higher than median baseline plasma potassium concentration (4.1 mmol/L). The median difference between those values was 0.4 mmol/L (95% CI, 0.2 to 0.5 mmol/L). Compared with their respective baseline measurements, the median serum plasma concentration (4.8 mmol/L) and median plasma potassium concentration (4.6 mmol/L) were higher after 20 to 28 hours of refrigeration.

CLINICAL RELEVANCE

Results indicated that with regard to potassium concentration in feline blood samples, clotting or refrigerated storage for 20 to 28 hours results in a significant artifactual increase. Detection of an unexpectedly high potassium concentration in a cat may represent pseudohyperkalemia, especially if the blood sample was placed in a no-additive tube, was stored for 20 to 28 hours prior to analysis, or both.

Sodium bicarbonate administration and subsequent potassium concentration in hyperkalemia treatment

BACKGROUND

Hyperkalemia is an electrolyte disorder commonly encountered in the emergency department that can result in significant morbidity and mortality. While sodium bicarbonate is often used for acute lowering of serum potassium, its efficacy is not well established. The purpose of this study was to evaluate and quantify the amount of potassium reduction in emergency department patients who received intravenous sodium bicarbonate as part of treatment for hyperkalemia compared with those who did not.

METHODS

A retrospective electronic chart review was conducted on adult patients who presented to the emergency department with initial potassium concentration greater than or equal to 5.4 mMol/L and received intravenous insulin as part of hyperkalemia treatment. Patients who received intravenous sodium bicarbonate in addition to intravenous insulin were included in the sodium bicarbonate group. The control group included patients who did not receive intravenous sodium bicarbonate. The primary objective of this study was to compare the absolute reduction in serum potassium between initial and second concentrations in patients from the sodium bicarbonate group and those in the control group.

RESULTS

A total of 106 patients were included in this study with 38 patients in the sodium bicarbonate group and 68 patients in the control group. Median initial potassium concentration was 6.6 mMol/L in the sodium bicarbonate group and 6.1 mMol/L in the control group (P = 0.009). Absolute reduction of potassium at first repeat was 1 and 0.9 mMol/L in sodium bicarbonate group and control group respectively (P = 0.976).

CONCLUSIONS

The addition of sodium bicarbonate therapy to intravenous insulin in the treatment of hyperkalemia did not offer statistically significant added efficacy in potassium lowering. Larger studies are needed to further validate the result findings.

Incidence, risk factors, and recognition of pseudohyperkalemia in patients with chronic lymphocytic leukemia

Pseudohyperkalemia, a false elevation of potassium level in vitro, can be observed in chronic lymphocytic leukemia (CLL) patients due to fragility of leukocytes along with a high leukocyte count. This retrospective, observational study included all patients diagnosed with CLL at our hospital who had at least one leukocyte count ≥ 50.0 × 10⁹/L during the years 2008-2018. All hyperkalemic episodes (including when leukocyte count was below 50.0 × 10⁹/L) during this period were assessed. Pseudohyperkalemia was defined as when a normal potassium level was measured in a repeated blood test or when known risk factors and ECG changes typical of hyperkalemia were absent. Of the 119 episodes of hyperkalemia observed, 41.2% were considered as pseudohyperkalemia. Pseudohyperkalemia episodes were characterized by significantly higher leukocyte counts as well as higher potassium and LDH levels compared to true hyperkalemia. Pseudohyperkalemia was documented in medical charts only in a minority of cases (n = 4, 8.1%). Treatment was administered in 17 of 49 (34.7%) cases and caused significant hypokalemia in 6 of those cases. The incidence of pseudohyperkalemia in this study was rather high, suggesting that physicians should be more aware of this phenomenon in patients with CLL.

Order of draw of blood samples affect potassium results without K-EDTA contamination during routine workflow

Introduction

A specific sequence is recommended for filling blood tubes during blood collection to prevent erroneous test results due to carryover of additives. However, requirement of this procedure is still debatable. This study was aimed to investigate the potassium ethylenediaminetetraacetic acid (K-EDTA) contamination in blood samples taken after a tube containing the additive during routine workflow. The study was also carried out to examine the effect of order of draw on potassium results, regardless of K-EDTA contamination.

Materials and methods

In 388 outpatients, to determine the probability of K-EDTA cross-contamination, blood was drawn sequentially into a serum tube, followed by a tube containing K-EDTA, and by another serum tube. In another 405 outpatients, to evaluate the effect of order of draw blood unrelated to K-EDTA contamination, two serum tube were successively collected. Potassium was measured on Cobas 6000 c501 analyser (Roche Diagnostic GmbH, Mannheim, Germany) by indirect ion selective electrode method.

Results

Of paired samples collected before and after a K-EDTA tube, 24% had a potassium difference of above 0.3 mmol/L. However, no EDTA contamination was detected in these samples as well as 95% confidence intervals (CI) of limits of agreement for calcium were within the allowable error limits based on reference change values. Interestingly, of blood samples drawn successively, 24% had also a difference greater than 0.3 mmol/L for potassium.

Conclusion

Incorrect order of draw using closed blood collection system does not cause K-EDTA contamination, even in routine workflow. However, regardless of K-EDTA contamination, order of draw has significant influence on the potassium results.

Abnormalities of Potassium in Heart Failure: JACC State-of-the-Art Review

Potassium (K⁺) is the most abundant cation in humans and is essential for normal cellular function. Alterations in K⁺ regulation can lead to neuromuscular, gastrointestinal, and cardiac abnormalities. Dyskalemia (i.e., hypokalemia and hyperkalemia) in heart failure is common because of heart failure itself, related comorbidities, and medications. Dyskalemia has important prognostic implications. Hypokalemia is associated with excess morbidity and mortality in heart failure. The lower the K⁺ levels, the higher the risk, starting at K⁺ levels below approximately 4.0 mmol/l, with a steep risk increment with K⁺ levels <3.5 mmol/l. Hyperkalemia (>5.5 mmol/l) has also been associated with increased risk of adverse events; however, this association is prone to reverse-causation bias as stopping renin angiotensin aldosterone system inhibitor therapy in the advent of hyperkalemia likely contributes the observed risk. In this state-of-the-art review, practical and easy-to-implement strategies to deal with both hypokalemia and hyperkalemia are provided as well as guidance for the use of potassium-binders.

The potential role of the eGFR in differentiating between true and pseudohyperkalaemia

BACKGROUND

Differentiating between true and pseudohyperkalaemia is essential for patient management. The common causes of pseudohyperkalaemia include haemolysis, blood cell dyscrasias and EDTA contamination. One approach to differentiate between them is by checking the renal function, as it is believed that true hyperkalaemia is rare with normal function. This is logical, but there is limited published evidence to support it. The aim of this study was to investigate the potential role of the estimated glomerular filtration rate in differentiating true from pseudohyperkalaemia.

METHODS

GP serum potassium results >6.0 mmol/L from 1 January 2017 to 31 December 2017, with a repeat within seven days, were included. Entries were retrospectively classified as true or pseudohyperkalaemia based on the potassium reference change value and reference interval. If the initial sample had a full blood count, it was classified as normal/abnormal to remove blood cell dyscrasias. Different estimated glomerular filtration rate cut-points were used to determine the potential in differentiating true from pseudohyperkalaemia.

RESULTS

A total of 272 patients were included with potassium results >6.0 mmol/L, with 145 classified as pseudohyperkalaemia. At an estimated glomerular filtration rate of 90 ml/min/1.73 m², the negative predictive value was 81% (95% CI: 67-90%); this increased to 86% (95% CI: 66-95%) by removing patients with abnormal full blood counts. When only patients with an initial potassium ≥6.5 mmol/L were included (regardless of full blood count), at an estimated glomerular filtration rate of 90 ml/min/1.73 m², the negative predictive value was 100%. Lower negative predictive values were seen with decreasing estimated glomerular filtration rate cut-points.

CONCLUSION

Normal renal function was not associated with true hyperkalaemia, making the estimated glomerular filtration rate a useful tool in predicting true from pseudohyperkalaemia, especially for potassium results ≥6.5 mmol/L.

Hyperkalemic Emergency: When You Have Taken a Few Too Many KCl Tablets

Hyperkalemia is a common clinical problem that varies significantly in severity and indications for treatment. Hyperkalemic emergency exists when there are clinical signs or symptoms, including cardiac conduction abnormalities. The combination of nebulized albuterol and insulin with glucose is most effective for managing clinically significant hyperkalemia. Prompt recognition of hyperkalemic emergency, immediate interventions to lower extracellular potassium, and involvement of multiple disciplines (including critical care and nephrology) are essential to addressing this life-threatening presentation.

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

OBJECTIVES

Preanalytical factors, such as hemolysis, affect many components of a test panel. Machine learning can be used to recognize these patterns, alerting clinicians and laboratories to potentially erroneous results. In particular, machine learning might identify which cases of elevated potassium from a point-of-care (POC) basic metabolic panel are likely erroneous.

METHODS

Plasma potassium concentrations were compared between POC and core laboratory basic metabolic panels to identify falsely elevated POC results. A logistic regression model was created using these labels and the other analytes on the POC panel.

RESULTS

This model has high predictive power in classifying POC potassium as falsely elevated or not (area under the curve of 0.995 when applied to the test data set). A rule-in and rule-out approach further improves the model's applicability with a positive predictive value of around 90% and a negative predictive value near 100%.

CONCLUSIONS

Machine learning has the potential to detect laboratory errors based on the recognition of patterns in commonly requested multianalyte panels. This could be used to alert providers at the POC that a result is suspicious or used to monitor the quality of POC results.

Etiology and Treatment of Intraoperative Hyperkalemia During Posterior Spinal Fusion in an Adolescent

Hyperkalemia, defined as a serum or plasma potassium greater than 5.5 mEq/L, while an uncommon occurrence in children, is a serious medical problem that warrants immediate attention as it can result in serious cardiac arrhythmias and death. Although hyperkalemia may occur in the critically ill patient or in the setting of renal failure and insufficiency, there are limited reports of its occurrence during intraoperative care. The authors report a previously healthy, 18-year-old patient, who developed hyperkalemia intraoperatively during posterior spinal fusion to treat adolescent idiopathic scoliosis. The potential etiologies of hyperkalemia are reviewed, a differential diagnosis for the possible etiologies presented, and treatment modalities discussed.

Comparative pharmacokinetics of maxacalcitol in healthy Taiwanese and Japanese subjects

Pharmacokinetic studies of maxacalcitol in healthy Taiwanese subjects have been conducted. This study to compare the pharmacokinetic properties of maxacalcitol in healthy Taiwanese and Japanese subjects. Healthy male Taiwanese subjects (n = 24) and healthy male Japanese subjects (n = 24) were enrolled in separate single-center and received a single intravenous dose of 1.25, 2.5 and 5 μg maxacalcitol. Male subjects were exclusively employed in the study due to the first administration of maxacalcitol to Taiwanese. Serum samples were collected for up to 72 h for pharmacokinetic analysis, and safety was assessed. Exposures to maxacalcitol as mean C₅ and AUC_inf appeared to increase with increase of doses in Taiwanese subjects (C₅: 74.0, 159, and 321 pg/mL; AUC_inf: 473, 763, and 1460 h･pg/mL) and Japanese subjects (C₅: 92.9, 174, and 346 pg/mL; AUC_inf: 312, 588, and 1040 h･pg/mL). After single bolus IV administration, linearity in maxacalcitol exposure was shown over the dose range of 1.25-5 μg in both Taiwanese and Japanese male healthy subjects. C₅ of maxacalcitol was slightly lower (85%) in Taiwanese compared with that in Japanese and AUC_inf of maxacalcitol in Taiwanese subjects was contrarily 15.0 (41.6%) higher than that in Japanese subjects, resulted in not much difference in pharmacokinetics of maxacalcitol between Taiwanese and Japanese. Moreover, maxacalcitol was well tolerated in both healthy Taiwanese and Japanese subjects.

Potassium disorders in pediatric emergency department: Clinical spectrum and management

INTRODUCTION

Potassium abnormalities are frequent in intensive care but their incidence in the emergency department is unknown.

AIM

We describe the spectrum of potassium abnormalities in our tertiary-level pediatric emergency department.

METHODS

Retrospective case-control study of all the patients admitted to a single-center tertiary emergency department over a 2.5-year period. We compared patients with hypokalemia (<3.0mEq/L) and patients with hyperkalemia (>6.0mEq/L) against a normal randomized population recruited on a 3:1 ratio with potassium levels between 3.5 and 5mEq/L.

RESULTS

Between January 1, 2013 and August 31, 2016 we admitted 108,209 patients to our emergency department. A total of 9342 blood samples were tested and the following potassium measurements were found: 60 cases of hypokalemia (2.8±0.2mEq/L) and 55 cases of hyperkalemia (6.4±0.6mEq/L). In total, 200 patients with normokalemia were recruited (4.1±0.3mEq/L). The main causes of the disorders were non-specific: lower respiratory tract infection (23%) and fracture (15%) for hypokalemia, lower respiratory tract (21.8%) and ear-nose-throat infections (20.0%) for hyperkalemia. Patients with hyperkalemia had an elevated creatinine level (0.72±1.6 vs. 0.40±0.16mg/dL, P<0.0001) with lower bicarbonate (19.4±3.8 vs. 21.8±2.8mmol/L, P=0.0001) and higher phosphorus levels (1.95±0.6 vs. 1.42±0.27mg/dL, P=0.0001). Patients with hypokalemia had an elevated creatinine level (0.66±0.71 vs. 0.40±0.16mg/dL, P<0.0001) and a lower phosphorus level (1.12±0.31 vs. 1.42±0.27mg/dL, P=0.0001). We did not observe significant differences in pH, PCO₂, base excess and lactate, or in the mean duration of hospitalization in general wards and pediatric intensive care units according to the PIM and PRISM scores.

DISCUSSION

Dyskalemia is rare in emergency department patients: 0.64% for hypokalemia and 0.58% for hyperkalemia. This condition could be explained by a degree of renal failure due to transient volume disturbance. The main mechanism is dehydration due to digestive losses, polypnea in young patients, and poor intake. In the case of hypokalemia, poor intake and digestive losses could be the main explanation. These disorders resolve easily with feeding or perfusion and do not impair development.

CONCLUSION

Dyskalemia is rare in emergency department patients and is easily resolved with feeding or perfusion. A plausible etiological mechanism is a transient volume disturbance. Dyskalemia is not predictive of poor development in the emergency pediatric population.

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.

Data-driven quality assurance to prevent erroneous test results

Increasing laboratory automation and efficiency requires quality assurance (QA) approaches to ensure that reported results are precise and accurate. Prerequisites for designing optimal QA strategies include an in-depth understanding of the laboratory processes, the expected results, and of the mechanisms that can cause erroneous results. Oftentimes, a laboratory's own data, extracted from the laboratory information system, electronic medical record, and/or clinical data warehouse are necessary to master the aforementioned requirements. Data-driven QA utilizes retrospective and/or prospective laboratory results to minimize errors in the clinical laboratory due to pre-analytical or analytical vulnerabilities. Additionally, exploitation of this data may improve result interpretation. The objective of this review is to illustrate specific examples of data-driven QA approaches for several areas of the clinical laboratory and for different phases of the testing cycle.

Spurious Laboratory Values in Patients With Leukocytosis

Physiological derangements such as hypoxemia and hyperkalemia are medical emergencies that warrant prompt interventions to prevent further patient clinical deterioration. However, in patients with myeloproliferative diseases or malignancies that result in extreme leukocytosis, hypoxemia and hyperkalemia demonstrated in laboratory results could be deceiving due to in vitro reactions and may not reflect actual patient condition. Clinicians have to be familiar with these phenomena so as to not cause harm by treating these spurious laboratory values.

Chronic Hyperkalemia in Cardiorenal Patients: Risk Factors, Diagnosis, and New Treatment Options

Chronic hyperkalemia (HK) is a serious medical condition that often manifests in patients with chronic kidney disease (CKD) and heart failure (HF) leading to poor outcomes and necessitating careful management by cardionephrologists. CKD, HF, diabetes, and renin-angiotensin-aldosterone system inhibitors use is known to induce HK. Current therapeutic options are not optimal, as pointed out by a large number of CKD and HF patients with HK. The following review will focus on the main risk factors for developing HK and also aims to provide a guide for a correct diagnosis and present new approaches to therapy.

Renal involvement in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most commonly diagnosed adult leukemia in the USA and Western Europe. Kidney disease can present in patients with CLL as a manifestation of the disease process such as acute kidney injury with infiltration or with a paraneoplastic glomerular disease or as a manifestation of extra renal obstruction and tumor lysis syndrome. In the current era of novel targeted therapies, kidney disease can also present as a complication of treatment. Tumor lysis syndrome associated with novel agents such as the B-cell lymphoma 2 inhibitor venetoclax and the monoclonal antibody obinutuzumab are important nephrotoxicities associated with these agents. Here we review the various forms of kidney diseases associated with CLL and its therapies.

Evidence-Based Validation of Hemolysis Index Thresholds by Use of Retrospective Clinical Data

Background

Semiquantitative hemolysis indices (HIs) are used by chemistry analyzers to measure sample integrity, but there is little standardization in HI reporting or validation of analyte-specific HI flagging. Additional methods of HI threshold validation are needed.

Methods

We retrospectively queried serum and plasma potassium measurements, HIs, and contemporaneous whole blood potassium measurements. Serum and plasma values were compared to whole blood values drawn within 6 h (n = 6422 pairs), and discrepancies between values were compared across HIs. We also retrieved orders of potassium-lowering medications occurring shortly after release of potassium results from hemolyzed samples.

Results

While nonhemolyzed samples showed high agreement, a significant percentage of released hemolyzed samples (36.1% of the most hemolyzed group) were discrepant by 1 mEq/L or more. In total, 15.5% of patients with an order from the hyperkalemia order set had the order after a hemolyzed value; the majority of those patients (42 of 46; 91.3%) received a potassium-lowering medication, most of whom did not have a redraw before drug administration.

Conclusions

Retrospective review of discrepancies identified marked inconsistencies among higher HI samples and identified opportunities for improving the laboratory reporting policy, offering a clinical validation of the HI thresholds for potassium. Clinicians generally treated patients with hemolyzed samples, underscoring the importance of maintaining sample quality.

Establishing evidence-based thresholds and laboratory practices to reduce inappropriate treatment of pseudohyperkalemia

BACKGROUND

Unrecognized pseudohyperkalemia (PHK), defined as an artificial increase in measured potassium concentration, due to thrombocytosis and leukocytosis can lead to inappropriate patient treatment. Understanding the laboratory and patient characteristics that increase risk of PHK is key to preventing diagnostic errors.

METHODS

Serum/plasma potassium results collected at 2 laboratories over 4years were selected based on blood cell counts collected within 24h and whole blood potassium concentrations determined within 2h of the serum/plasma sample. Differences between whole blood and serum or plasma potassium were compared as functions of platelet or leukocyte count, fit to linear models, and stratified based on leukemia diagnosis codes. Patients having a serum/plasma potassium concentration that was at least 1mEq/mL higher than the whole blood concentration were defined as having PHK. Based on this analysis, high-risk patients were prospectively identified and PHK risk was communicated to providers. Medication administration records were queried to compare rates of kayexalate use pre- and post-intervention.

RESULTS

Approximately 14% of serum samples with platelet counts >500×10⁹/L had a>1mEq/L increase relative to whole blood potassium. >25% of serum and plasma samples showed a>1mEq/L increase relative to whole blood potassium when leukocyte counts were >50×10⁹/L. Patients with chronic lymphocytic leukemia and high WBC count demonstrated the highest rates of PHK. The rate of kayexalate administration prior to confirmatory testing decreased from 37% to 16% after the laboratory started verbally communicating the possibility of PHK to treating providers.

CONCLUSIONS

According to our data, a leukocyte count threshold for plasma samples of 50×10⁹/L is appropriate for indicating a high risk of PHK. Direct communication by the laboratory to the care team reduces inappropriate potassium lowering treatment in populations at high risk.

Electrolyte and Acid-Base Disorders in Chronic Kidney Disease and End-Stage Kidney Failure

The kidneys play a pivotal role in the regulation of electrolyte and acid-base balance. With progressive loss of kidney function, derangements in electrolytes and acid-base inevitably occur and contribute to poor patient outcomes. As chronic kidney disease (CKD) has become a worldwide epidemic, medical providers are increasingly confronted with such problems. Adequate diagnosis and treatment will minimize complications and can potentially be lifesaving. In this review, we discuss the current understanding of the disease process, clinical presentation, diagnosis and treatment strategies, integrating up-to-date knowledge in the field. Although electrolyte and acid-base derangements are significant causes of morbidity and mortality in CKD and end-stage renal disease patients, they can be effectively managed through a timely institution of combined preventive measures and pharmacological therapy. Exciting advances and several upcoming outcome trials will provide further information to guide treatment and improve patient outcomes.

Variability in, variability out: best practice recommendations to standardize pre-analytical variables in the detection of circulating and tissue microRNAs

microRNAs (miRNAs) hold promise as biomarkers for a variety of disease processes and for determining cell differentiation. These short RNA species are robust, survive harsh treatment and storage conditions and may be extracted from blood and tissue. Pre-analytical variables are critical confounders in the analysis of miRNAs: we elucidate these and identify best practices for minimizing sample variation in blood and tissue specimens. Pre-analytical variables addressed include patient-intrinsic variation, time and temperature from sample collection to storage or processing, processing methods, contamination by cells and blood components, RNA extraction method, normalization, and storage time/conditions. For circulating miRNAs, hemolysis and blood cell contamination significantly affect profiles; samples should be processed within 2 h of collection; ethylene diamine tetraacetic acid (EDTA) is preferred while heparin should be avoided; samples should be “double spun” or filtered; room temperature or 4 °C storage for up to 24 h is preferred; miRNAs are stable for at least 1 year at –20 °C or –80 °C. For tissue-based analysis, warm ischemic time should be <1 h; cold ischemic time (4 °C) <24 h; common fixative used for all specimens; formalin fix up to 72 h prior to processing; enrich for cells of interest; validate candidate biomarkers with in situ visualization. Most importantly, all specimen types should have standard and common workflows with careful documentation of relevant pre-analytical variables.

Spurious elevation of serum potassium concentration measured in samples with thrombocytosis

BACKGROUND

Several factors that can lead to falsely elevated values of serum. Thrombocytosis is one of these factors, since breakage or activation of platelets during blood coagulation in vitro may lead to spurious release of potassium. The purpose of the study was to evaluate to which extent the platelet count may impact on potassium in both serum and plasma.

METHODS

The study population consisted of 42 subjects with platelets values comprised between 20 and 750×109/L. In each sample potassium was measured in both serum and plasma using potentiometric indirect method on the analyzer Modular P800 (Roche, Milan, Italy). Platelet count was performed with the hematological analyzer Advia 120 (Siemens, Milano, Italy).

RESULTS

Significant differences were found between potassium values in serum and in plasma. A significant correlation was also observed between serum potassium values and the platelet count in whole blood, but not with the age, sex, erythrocyte and leukocyte counts in whole blood. No similar correlation was noticed between plasma potassium and platelet count in whole blood. The frequency of hyperkalemia was also found to be higher in serum (20%) than in plasma (7%) in samples with a platelet count in whole blood >450×109/L.

CONCLUSIONS

The results of this study show that platelets in the biological samples may impact on potassium measurement when exceeding 450×109/L. We henceforth suggest that potassium measurement in plasma may be more accurate than in serum, especially in subjects with thrombocytosis.