Pseudohyperkalemia Due to Pneumatic Tube Transport in a Leukemic Patient

Pneumatic tube transport-induced pseudohyperkalemia in patients with extreme leukocytosis: a retrospective study from a single medical center

BACKGROUND

Pseudohyperkalemia (falsely elevated serum potassium) must be distinguished from true hyperkalemia to avoid unnecessary treatment. Some case reports suggest that pneumatic tube transportation may increase the risk of pseudohyperkalemia, but comprehensive research on the topic is lacking. Here, we aimed to assess the association between WBC levels, pneumatic tube transport, and pseudohyperkalemia prevalence.

METHODS

We analyzed 1188 samples collected from 240 patients between 2019 and 2022. Samples with elevated WBC counts (≥ 100 × 103/μL) and potassium levels were included in this study. The method of specimen transportation was documented.

RESULTS

Pseudohyperkalemia was observed (7/390) in specimens transported using pneumatic tubes. No pseudohyperkalemia was identified with manually transported specimens (0/132). Every increase in WBC count by 100 × 103/μL in the specimens multiplied the odds ratio of pseudohyperkalemia by 3.75 when delivered with pneumatic tube. The prevalence of pseudohyperkalemia increased as WBC count increased, especially at WBC counts greater than 200 × 103/μL.

CONCLUSION

Pneumatic tube transport poses a risk for pseudohyperkalemia in patients with extreme leukocytosis. Physicians should anticipate odd potassium levels when interpreting blood test results. Redrawing of blood samples, manual specimen transportation, or point-of-care testing are suggested to prevent further misdiagnosis.

Manual flagging failed to identify pseudohyperkalemia in acute myeloid leukemia: case report

BACKGROUND

Pseudohyperkalemia is well known in acute or chronic lymphocytic leukemia, but it is very rare in acute myeloid leukemia (AML). The lab flagging system for leukocytosis to prevent pseudohyperkalemia may not work.

CASE PRESENTATION

A 55 year-old white man with AML was sent to emergency department for transfusion due to severe anemia. Blood test showed severe leukocytosis and elevated potassium. Repeated blood test showed his potassium was even higher. Anti-hyperkalemic medical treatment was given. He was then diagnosed with pseudohyperkalema.

INVESTIGATION

I was repeatedly reassured that the lab's manual flagging system for leukocytosis was the key in reaching the correct diagnosis. My persistent inquiries, however, revealed that the flagging system was not functioning in the care of this patient. It was clinicians' suspicion of pseudohyperkalema that led to the correct diagnosis, although the clinicians' recommendation of obtaining a heparinized plasma for test did not play a role because all blood samples were already heparinized. The cause of pseudohyperkalemia was pneumatic tube transport. After this incident, our laboratory is investigating the options of using the Laboratory Information System to automatically flag the results and Clinical Laboratory Scientists to make the chemistry team more aware of potentially erroneous potassium results due to pseudohyperkalemia.

CONCLUSIONS

Pseudohyperkalemia associated with leukocytosis still occurs. This is the first case of pneumatic tube transport causing pseudohyperkalemia associated with AML. When significant leukocytosis, thrombocytosis, hyperproteinemia, or hyperlipidemia is present, whole blood should be utilized for potassium measurements and walked to the lab instead of sent by pneumatic tube transport. Even in a lab with a manual flagging system, there is still room to improve by implementing an automatic flagging system.

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.

Erroneous potassium results: preanalytical causes, detection, and corrective actions

Potassium is one of the most requested laboratory tests. Its level is carefully monitored and maintained in a narrow physiological range. Even slightly altered potassium values may severely impact the patient's health, which is why an accurate and reliable result is of such importance. Even if high-quality analytics are available, there are still numerous ways in which potassium measurements may be biased, all of which occur in the preanalytical phase of the total laboratory testing process. As these results do not reflect the patient's in-vivo status, such results are referred to as pseudo-hyper/hypokalemia or indeed pseudo-normokalemia, depending on the true potassium result. Our goal in this review is to present an in-depth analysis of preanalytical errors that may result in inaccurate potassium results. After reviewing existing evidence on this topic, we classified preanalytical errors impacting potassium results into 4 categories: 1) patient factors like high platelet, leukocytes, or erythrocyte counts; 2) the sample type 3) the blood collection procedure, including inappropriate equipment, patient preparation, sample contamination and others and 4) the tube processing. The latter two include sample transport and storage conditions of whole blood, plasma, or serum as well as sample separation and subsequent preanalytical processes. In particular, we discuss the contribution of hemolysis, as one of the most frequent preanalytical errors, to pseudo-hyperkalemia. We provide a practical flow chart and a tabular overview of all the discussed preanalytical errors including possible underlying mechanisms, indicators for detection, suggestions for corrective actions, and references to the according evidence. We thereby hope that this manuscript will serve as a resource in the prevention and investigation of potentially biased potassium results.

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.

Spurious Electrolyte and Acid-Base Disorders in the Patient With Cancer: A Review

Electrolyte and acid-base disorders are frequently encountered in patients with malignancy, either due to cancer itself or as a complication of its therapy. However, spurious electrolyte disorders can complicate the interpretation and management of these patients. Several electrolytes can be artifactually increased or decreased such that the serum electrolyte values do not correspond to their actual systemic levels, potentially resulting in extensive diagnostic investigations and therapeutic interventions. Examples of spurious derangements include pseudohyponatremia, pseudohypokalemia, pseudohyperkalemia, pseudohypophosphatemia, pseudohyperphosphatemia, and artifactual acid-base abnormalities. Correctly interpreting these artifactual laboratory abnormalities is imperative for avoiding unnecessary and potentially harmful interventions in cancer patients. The factors influencing these spurious results also must be recognized, along with the steps to minimize them. We present a narrative review of commonly reported pseudo electrolyte disorders and describe strategies to exclude erroneous interpretations of these laboratory values and avoid pitfalls. Awareness and recognition of spurious electrolyte and acid-base disorders can prevent unnecessary and harmful treatments.

Managing Hyperkalemia in the Modern Era: A Case-Based Approach

The last decade has seen tremendous advances in the prevention and treatment of recurrent hyperkalemia. In this narrative review, we aim to highlight contemporary data on key areas in the epidemiology and management of hyperkalemia. Focusing on drug-induced hyperkalemia (the implications of renin-angiotensin-aldosterone system inhibitors [RAASi] discontinuation and the role of mineralocorticoid receptor antagonists), newer concurrent therapies that modify potassium handling (sodium-glucose transporter 2 inhibitors [SGLT2i]), the introduction of new treatment agents (oral potassium binding agents), and the controversial role of dietary potassium restriction, we apply recent research findings and review the evidence in a case-based format.

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.

Electrolytes disturbances in cancer patients

PURPOSE OF REVIEW

Hypernatremia, hyperphosphatemia, hypocalcaemia, hyperkalaemia and hypermagnesemia are electrolytes disturbances that can arise in cancer patients in relation to unique causes that are related to the cancer itself or its treatment and can lead to delay or interruption of cancer therapy. This article summarizes these main causes, the proposed pathophysiology and the recommended management for these disturbances.

RECENT FINDINGS

There have been many cancer drugs approved in the field of oncology over the past several years and a subset of these drugs have been associated with electrolytes disturbances. This includes, for example, immune checkpoint inhibitor related hyperkalemia, fibroblast growth factor 23 inhibitor associated hyperphosphatemia and epidermal growth factor receptor inhibitor associated hypomagnesemia and hypocalcaemia.

SUMMARY

This article provides an updated review of certain electrolytes disturbance in cancer patients and allows clinicians to have a greater awareness and knowledge of these electrolyte abnormalities in efforts to early recognition and timely management.

Investigation of the effects of pneumatic tube transport system on routine biochemistry, hematology, and coagulation tests in Ankara City Hospital

OBJECTIVES

Academics are far from a consensus regarding the effects of pneumatic tube system (PTS) delivery on sample integrity and laboratory test results. As for the reasons for conflicting opinions, each PTS is uniquely designed, sample tubes and patient characteristics differ among studies. This study aims to validate the PTS utilized in Ankara City Hospital for routine chemistry, coagulation, and hematology tests by comparing samples delivered via PTS and porter.

METHODS

The study comprises 50 healthy volunteers. Blood samples were drawn into three biochemistry, two coagulation, and two hemogram tubes from each participant. Each of the duplicate samples was transferred to the emergency laboratory via Swiss log PTS (aka PTS-immediately) or by a porter. The last of the biochemistry tubes were delivered via the PTS, upon completion of coagulation of the blood (aka PTS-after). The results of the analysis in these groups were compared with multiple statistical analyses.

RESULTS

The study did not reveal any correlation between the PTS and serum hemolysis index. There were statistically significant differences in several biochemistry tests. However, none of them reached the clinical significance threshold. Basophil and large unidentified cell (LUC) tests had poor correlations (r=0.47 and r=0.60; respectively) and reached clinical significance threshold (the average percentages of bias, 10.2%, and 15.4%, respectively). The remainder of the hematology and coagulation parameters did not reach clinical significance level either.

CONCLUSIONS

The modern PTS validated in this study is safe for sample transportation for routine chemistry, coagulation, and hematology tests frequently requested in healthy individuals except for basophil and LUC.

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.

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.

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.

Reverse pseudohyperkalemia is more than leukocytosis: a retrospective study

BACKGROUND

Hyperkalemia is a potentially life-threatening electrolyte abnormality that often requires urgent treatment. Clinicians should distinguish true hyperkalemia from pseudohyperkalemia and reverse pseudohyperkalemia (RPK). RPK has exclusively been described in case reports of patients with hematologic malignancies (HMs) and extreme leukocytosis [white blood cell (WBC) count >200 × 103/mL].

METHODS

This single-center retrospective study analyzed laboratory data from the Mount Sinai Data Warehouse between 1 January 2010 and 31 December 2016 for plasma potassium and serum potassium samples drawn within 1 h of each other, with plasma potassium ≥1 mEq/L of the serum potassium. Only plasma potassium ≥5 mEq/L were included. Samples that were documented to be hemolyzed or contaminated were excluded. Clinical history and laboratory data were collected from the identified cases.

RESULTS

After applying the inclusion/exclusion criteria to 485 potential cases, the final cohort included 45 cases from 41 patients. There were 24 men and 17 women with a mean age of 52 years. The median plasma potassium was 6.1 mEq/L and serum potassium was 4.4 mEq/L. The median WBC count was 9.35 × 103/mL (interquartile range 6.5-19.7 × 103/mL). Only 44% of the samples had leukocytosis, defined as WBC >11 × 103/mL.Seven patients had a HM and comprised 11 of the cases (24%) with a median WBC of 181.8 × 103µL. There was no difference in their plasma and serum potassium levels when compared with the total cohort, despite a higher median WBC count. Thirty-eight percent of the cases required medical management.

CONCLUSIONS

The literature on RPK is limited to case reports and series associated with extreme leukocytosis. This is the first study characterizing RPK predominantly associated with normal leukocyte counts. Further investigation is required to more precisely characterize factors associated with RPK and to elucidate RPK mechanisms.

[Pseudohyperkalemia and thrombocytosis]

INTRODUCTION

Hyperkalemia is common in medicine and requires rapid management. Besides the easily evoked causes such as renal failure, adrenal insufficiency, cell lysis or iatrogenic causes, false or pseudo-hyperkalemia should not be forgotten.

OBSERVATIONS

Three patients (1 man, 2 women, aged 78, 84, 88) were managed for thrombocytosis (between 1306 and 2404 G/L) and non-symptomatic hyperkalemia (between 6.1 and 7.7mmol/L) are reported. Kalemia on blood collected in heparin tube was normal (4.4-4.6mmol/L). Therefore, no specific treatment for this pseudohyperkalemia was required.

CONCLUSION

The combination of thrombocytosis and non-symptomatic hyperkalemia should suggest the diagnosis of pseudohyperkalemia and should prompt for a control of kalemia on blood collected in heparin tube. The recognition of this diagnosis is important in order to avoid unnecessary and potentially deleterious treatment of hyperkalemia.

Reverse pseudohyperkalemia and pseudohyponatremia in a patient with B-cell non-Hodgkin lymphoma

OBJECTIVES

Investigate concomitant and spurious high potassium and low sodium results in heparinized plasma.

METHODS

Potassium and sodium values were measured from heparinized plasma and serum in a patient with B-cell non-Hodgkin lymphoma using both an automated chemistry analyzer (indirect ion selective electrode) and blood gas analyzer (direct ion selective electrode).

RESULTS

Potassium levels were significantly increased while sodium levels were significantly decreased in heparinized plasma compared to serum on several occasions.

CONCLUSIONS

To our knowledge, concomitant reverse pseudohyperkalemia and pseudohyponatremia has not been reported previously. We postulate the discrepancy between plasma and serum sodium (pseudohyponatremia in plasma) may be unique to cases of reverse pseudohyperkalemia with extreme potassium elevations.

Management of electrolyte disorders: also the method matters!

Introduction: For the last few decades, electrolyte determinations in plasma or serum are carried out by reliable potentiometric methods. In recent years, a marked technical evolution has taken place, where the clinical analysis of common analytes (e.g. electrolytes) is partly moving from centralised clinical core laboratories to near-patient point-of-care testing. Methods: As the measuring principle used by point-of-care testing markedly differs from the one used in core laboratories, sodium results are not always interchangeable in critically ill patients due to the different sensitivity of the analytical methods for the electrolyte exclusion effect. Results: This effect mainly occurs in patients with decreased plasma protein values. The observed differences in generated test results might significantly affect the judgment and the treatment of electrolyte disturbances. As technical solutions are not likely to occur in the near future, clinicians and laboratorians should be well aware of this growing problem. Mathematical correction of the sodium results for plasma protein concentration may resolve the problem to a certain extent. Discussion: Although electrolyte determinations are generally very reliable, analytical interferences can occur for sodium rarely, mainly due to contamination by surfactants, benzalkonium in particular. For potassium, the major problem is hemolysis. To a lesser extent, leukocyte lysis and thrombocytopenia may also interfere. For chloride determination, the selectivity of the electrodes used is not ideal. Occasionally, false positive signals can be observed in presence of interfering ions (e.g. bromide).

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.

Pseudohyperkalemia: Hyperkalemia Cocktail or Alternative Diagnosis

Introduction

Hyperkalemia is a commonly encountered clinical problem. Pseudohyperkalemia is believed to be an in vitro phenomenon that does not reflect in vivo serum potassium and therefore should not be treated. Here, we present a case who unfortunately underwent unnecessary treatment because of failure to detect the common lab abnormality of pseudohyperkalemia.

Case Presentation

A 91-year-old female with a history of chronic lymphocytic leukemia presented to the emergency with nausea and vomiting 24 hours after her first chemotherapy with chlorambucil. Physical examination was overall unremarkable. She had a leukocytosis of 210 × 10³/µL with 96% lymphocytes along with chronic anemia with hemoglobin of 8.1 g/dL. Her initial sodium and potassium levels were normal. During the clinical course, her potassium progressively worsened and failed to improve despite standard medical treatment. Patient ultimately underwent dialysis.

Conclusions

Differentiating true hyperkalemia from pseudohyperkalemia is very important in selected group of patients to avoid unnecessary medications, higher level of care, and unnecessary procedure including dialysis. We want to emphasize the importance of simple yet profound knowledge of technique of blood draws and basic metabolic panel processing for every clinician in day-to-day practice.

[Safe treatment of acute hyperkalemia : The 1:4 and other principles]

Acute hyperkalemia is a dangerous electrolyte disorder, which must be treated immediately. It can lead to cardiac arrhythmia and death due to alterations in cell membrane potentials. The resulting alterations in the electrocardiogram (ECG) are multifarious and need to be rapidly recognized. Treatment consists of various stages. In addition to membrane stabilization, which is always necessary, potassium must be displaced into the intracellular space and then eliminated from the body. A commonly applied method for displacement of potassium into the intracellular space involves the administration of insulin-glucose mixtures, which is associated with many complications. In the clinical routine many prescription variations are applied, which do not always appear to be ideal with respect to the individual risk-benefit ratio. A practically useful and easily memorized insulin-glucose mixture has a relationship of 1IU insulin to 4g glucose. The therapeutic elimination from the body is carried out using an enhanced diuresis or the utilization of renal replacement procedures. Special attention must be paid to the continous monitoring of potassium and blood sugar levels. After overcoming the acute situation, attention must be paid to treatment of the underlying disorder and if necessary to readjustment of the long-term medication of the patient.

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.

Reverse pseudohyperkalemia in a patient with chronic lymphocytic leukemia

A man, age 78 years, with a history of chronic lymphocytic leukemia presented to clinic for evaluation of a cough. On further evaluation, he was noted to have an elevated potassium level. This case report highlights the importance of distinguishing cases of true hyperkalemia from pseudohyperkalemia and reverse pseudohyperkalemia.

Comparison of red blood cell hemolysis using plasma and serum separation tubes for outpatient specimens

Background

To rapidly obtain outpatient results, we use plasma separation tubes (PST) for chemistry analysis. If lactate dehydrogenase measurement is required, serum separation tubes (SST) are used. There has been no evaluation of hemolysis with these tubes. We compared the hemolytic index (HI) obtained by using PST and SST and applied this for choosing appropriate tubes for clinical laboratories.

Methods

The HI of specimens obtained from outpatients visiting Asan Medical Center between July and December 2012 was analyzed. The HI was scored from 0 to 10 by using the Toshiba 200FR (Toshiba Medical Systems Co., Japan). HI was classified by sample tube type, and significant hemolysis was defined as a HI of 2 or more. For significant hemolysis cases, medical records were reviewed to identify the causes.

Results

Among 171,519 specimens, significant hemolysis was observed in 0.66% of specimens (0.68% of PST specimens, 0.46% of SST specimens). The mean HI in PST was 0.18 (SD: 0.43) and that in SST was 0.14 (SD: 0.37). The proportion of significant hemolysis was significantly higher in PST than in SST (P=0.001). The cause of significant hemolysis was identified as chemotherapy and prosthetic valve in 48.1% of specimens. Complex sampling errors may have caused significant hemolysis in the remaining 51.9% of specimens.

Conclusions

The incidence of hemolysis was slightly higher for PST than SST, although both were <1%. PST are thought to be more useful than SST in outpatient testing because of rapid turnaround time, greater sample volume, and less risk of random errors due to fibrin strands.

Errors in potassium measurement: a laboratory perspective for the clinician

Errors in potassium measurement can cause pseudohyperkalemia, where serum potassium is falsely elevated. Usually, these are recognized either by the laboratory or the clinician. However, the same factors that cause pseudohyperkalemia can mask hypokalemia by pushing measured values into the reference interval. These cases require a high-index of suspicion by the clinician as they cannot be easily identified in the laboratory. This article discusses the causes and mechanisms of spuriously elevated potassium, and current recommendations to minimize those factors. "Reverse" pseudohyperkalemia and the role of correction factors are also discussed. Relevant articles were identified by a literature search performed on PubMed using the terms "pseudohyperkalemia," "reverse pseudohyperkalemia," "factitious hyperkalemia," "spurious hyperkalemia," and "masked hypokalemia."

Effect of blood collection tubes on the incidence of artifactual hyperkalemia on patient samples from an outreach clinic

BACKGROUND

An offsite satellite clinic of the University of Chicago Medical Center (UCMC) requested an investigation by the Clinical Chemistry Laboratory (CCL) into several cases of possible falsely elevated potassium (K⁺) values in their patients. Bloods for K⁺ and chemistry profiles are routinely collected in mint-green, heparinized plasma separator tubes (PST), centrifuged, and transported by courier from satellite clinic to CCL within several hours. Samples from on-site phlebotomy areas are similarly collected but sent uncentrifuged to CCL via a pneumatic tube system within minutes of collection.

METHODS

Our investigations included extensive QC and QA review of UCMC onsite and offsite outpatient clinics, reference range studies using PST and serum separator tubes (SST), assessment of pre-analytic handling of specimens, including transportation simulation study, and comparison of K⁺ results for samples collected simultaneously using PST and SST tubes at an offsite clinic.

RESULTS

Our transportation simulation demonstrated elevations in K⁺ concentrations following sample jostling and perturbations. We also observed RBC escape across the gel barrier further contributing to K⁺ elevations.

CONCLUSION

Serum is preferred sample type for an offsite clinic.

Pseudohyperkalemia from a Pneumatic Tube Transport System: Case Report and Literature Review

Objective

To report a case of pseudohyperkalemia due to a pneumatic tube transport system.

Case Summary

A 75-year-old male presented to the emergency medicine department with chest pain and intermittent vision loss over the previous 2 days. Laboratory studies revealed a potassium value of 9.6 mEq/L and a white blood cell (WBC) count of 262 × 109/L. An electrocardiogram did not reveal changes consistent with hyperkalemia. Emergent treatment for the hyperkalemia was instituted. Repeat plasma potassium values obtained after treatment for the hyperkalemia remained significantly elevated. It was eventually recognized that the hyperkalemia was due to the combination of undiagnosed leukemia causing a significantly elevated WBC count and transport of the patient's specimen to the laboratory via a pneumatic tube transport system. Manual transport of the specimen to the laboratory repeatedly revealed normal or hypokalemic values.

Discussion

Hyperkalemia is a potentially fatal electrolyte abnormality that must be differentiated from pseudohyperkalemia. Pseudohyperkalemia is defined as a spurious elevation of potassium levels usually due to mechanical trauma during venipuncture resulting in hemolysis and release of potassium from the cellular elements of blood. Pneumatic tube transport systems should be listed in the scientific literature as another potential cause of pseudohyperkalemia, especially in patients with high WBC and/or platelet counts.

Conclusion

Pharmacists and other health care providers should be aware of pneumatic tube transport systems potentially causing pseudohyperkalemia, because regular treatments for hyperkalemia for this problem may cause patient harm.

Pseudohyperkalemia without reported haemolysis in a patient with chronic lymphocytic leukaemia

Hyperkalemia is a medical condition that requires immediate recognition and treatment to prevent the development of life-threatening arrhythmias. Pseudohyperkalemia is most commonly due to specimen haemolysis and is often recognised by laboratory scientists who subsequently report test results with cautionary warnings. The authors present a case of pseudohyperkalemia in a patient with chronic lymphocytic leukaemia that was the result of white blood cell lysis during phlebotomy. False elevations of potassium from this condition may not be reported with a warning from the laboratory. This places the patient at risk of unnecessary and potentially dangerous treatments. This phenomenon has not been published in the emergency medicine literature to date.

Pseudohyperkalemia in a patient with chronic lymphoblastic leukemia and tumor lysis syndrome

Purpose:

Recognition of pseudohyperkalemia is essential to prevent medical mismanagement of erroneous hyperkalemia. The purpose of this case is to describe pseudohyperkalemia attributed to malignant leucocytosis in a patient with chronic lymphoblastic leukemia and tumor lysis syndrome. Methods for determination of pseudohyperkalemia are discussed.

Summary:

A 75-year-old male with progressive chronic lymphoblastic leukemia was hospitalized for medical evaluation and chemotherapy administration. Notable laboratory findings included white blood cell count of 479 × 103 cells/µL (4.00 × 103 cells/µL–10.80 × 103 cells/µL) with 95% lymphocytes (20%–50%) and 5% blasts (zero) present in the differential, serum potassium 9.8 mM/L (3.4 mM/L–5.0 mM/L), uric acid of 11.8 mg/dL (3.5 mg/dL–8.0 mg/dL), serum creatinine 1.47 mg/dL (0.60 mg/dL–1.30 mg/dL), and lactate dehydrogenase of 2529 IU/L (100 IU/L–220 IU/L). The patient was anemic (Hb 7.6 g/dL (14.0 g/dL–18.0 g/dL)) and thrombocytopenic (17 × 103 platelets/μL (140 × 103 platelets/μL–400 × 103 platelets/μL)). There were no electrocardiographic findings indicating systemic hyperkalemia. Repeat analysis of the blood potassium level using a heparinized tube assayed immediately after specimen collection demonstrated a plasma potassium level 4.1 mM/L. Subsequent analysis of specimens using similar methodology demonstrated potassium results within the normal limits despite continued laboratory evidence of pseudohyperkalemia. Based on the patient’s conscious and interactive condition, ECG findings, and normal plasma potassium level following immediate analysis, the diagnosis of pseudohyperkalemia was made. Laboratory findings of pseudohyperkalemia persisted throughout the period of leukocytosis.

Conclusion:

This case describes pseudohyperkalemia attributed to malignant leucocytosis in a patient with chronic lymphoblastic leukemia (CLL). Practitioners should consider pseudohyperkalemia as the underlying cause of elevated potassium levels in patients with malignant leucocytosis who do not have signs or symptoms of systemic hyperkalemia.

Pseudohyperkalemia in patients with chronic lymphocytic leukemia

Pseudohyperkalemia occurs occasionally in patients with extreme leukocytosis. Increased white blood cell fragility coupled with mechanical stress is felt to be causal. Serum and plasma potassium levels have been both associated with pseudohyperkalemia. Whole blood potassium determination will usually verify the correct diagnosis. It is important to diagnose this condition early so that patients are not inappropriately treated. Two patients with chronic lymphocytic leukemia and extreme leukocytosis are presented, one with pseudohyperkalemia and one with probable pseudohyperkalemia, and diagnostic considerations are discussed

Ion Selective Electrodes (ISEs) and interferences--a review

Ion Selective Electrodes (ISEs) are used to measure some of the most critical analytes on clinical laboratory and point-of-care analysers. These analytes which include Na(+), K(+), Cl(-), Ca(2+), Mg(2+) and Li(+) are used for rapid patient care decisions. Although the electrodes are very selective, they are not free of interferences. It is important for laboratories to have an understanding of the type and extent of interferences in order to avoid incorrect clinical decisions and treatment.

Pneumatic transport is critical for leukaemic patients with major leukocytosis: what precautions to measure lactate dehydrogenase, potassium and aspartate aminotransferase?

False elevations of plasma lactate dehydrogenase (LDH), potassium and aspartate aminotransferase (AST) have been described, in relation to haemolysis, occurring most often by mechanical release during phlebotomy or specimen processing. We present the cases of two leukaemic patients with severe hyperleukocytosis for whom LDH, potassium and AST were dramatically but falsely elevated. This false elevation was not caused by haemolysis but could be related to white cells lysis during transport through a pneumatic transportation system, enhanced by a specific fragility of leukaemic cells. Interestingly, this interference almost completely disappeared when serum rather than plasma was used, or when leukocytosis came back to normal. This work is meant to alert clinicians to the risks of errors in LDH, potassium and AST in leukaemic patients and suggest what precautions to take.

Factitious biochemical measurements resulting from hematologic conditions

Factitious laboratory results often lead to unnecessary testing or treatment. This brief review of factitious biochemical results due to preexisting hematologic conditions focuses on the mechanisms underlying the factitious results and suggests ways to prevent them. An observant pathologist identifies these errors, intervenes in a timely fashion, investigates the sources of error diligently, and institutes measures to prevent their recurrence.