Reverse Pseudohyperkalemia: An Important Clinical Entity in Chronic Lymphocytic Leukemia

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 and diabetic ketoacidosis

Pseudohyperkalemia can lead to inaccurate hyperkalemia diagnosis, inappropriate initiation of potassium-lowering therapies, and overall unnecessary treatment possibly inducing iatrogenic hypokalemia. Patients with leukocytosis and thrombocytosis should raise clinical suspicion that hyperkalemic laboratory results in the absence of other traditional signs of hyperkalemia may be indicative of pseudohyperkalemia. Here we present a case of severe leukocytosis with chronic lymphocytic leukemia (CLL) found to have critically elevated potassium levels on admission to the intensive care unit (ICU). The patient was also diagnosed with diabetic ketoacidosis (DKA) at admission, requiring an increased frequency of electrolyte monitoring. The events leading to the prompt recognition of pseudohyperkalemia in this patient will be delineated alongside our recommendations for revising the institutional protocol to avoid false hyperkalemia diagnoses in patients with CLL.

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.

False, Reversed but Not True: A Curious Case of Hyperkalemia

Falsely elevated potassium levels are common in routine laboratory tests and should be differentiated from true hyperkalemia. If the patient is inappropriately treated for hyperkalemia, the resulting hypokalemia can lead to life-threatening cardiac arrhythmias. We present the case of a 67-year-old woman with a past medical history of stable chronic lymphocytic leukemia, who presented for chest pain and had an elevated potassium level of 5.8 mEq/L, which, upon repeat laboratory testing, was then 6.7 mEq/L. She was initially treated for hyperkalemia. Laboratory test results showed creatine kinase levels at 43 U/L, lactate dehydrogenase levels at 177 U/L, phosphorus levels at 4.5 mg/dL, and uric acid levels at 6.4 mg/dL, indicating no evidence of tumor lysis syndrome. The patient was later diagnosed with reverse pseudohyperkalemia, indicated by falsely elevated plasma potassium levels in the presence of serum potassium levels within normal limits and venous blood gas samples.

Pseudohyperkalemia in Serum and Plasma: The Phenomena and Its Clinical Implications

Hyperkalemia is a life threatening electrolyte derangement that must be recognized and treated quickly. Pseudohyperkalemia is defined as a difference between serum and plasma potassium concentration of more than 0.4 meq/L with serum values on the higher side when both the samples are obtained at the same time, remain at room temperature and are tested within 1 h of sample collection. Given the implication of basing medical decisions on falsely elevated potassium levels, timely identification of the entity of pseudohyperkalemia and differentiating it from true hyperkalemia becomes utmost important. Here we present a case report of a 36 year old female admitted with a provisional diagnosis of pyrexia of unknown origin with hepatosplenomegaly and anaemia under evaluation. During hospital stay her potassium levels in whole blood, serum and plasma reportedly differed significantly. An abnormal WBC count beyond assay range was reported and during subsequent investigations this lead to a peripheral smear being advised and diagnosis revealed chronic lymphoblastic leukaemia with blast crisis and 86% blast cells. In patients with leukocytosis and thrombocytosis, pseudohyperkalemia may exist in the absence of electrocardiogram changes or other clinical manifestations of true hyperkalemia thus leading to reevaluation of potassium values in serum, plasma and whole blood to arrive at the true picture.

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.