Pseudohyperkalemia: Look before you treat

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 and the Need for Imperative Caution With the Newly Introduced Potent Potassium Binders: Two Cases

Pseudohyperkalemia was first reported in 1955 by Hartmann and Mellinkoff, as a marked elevation of serum potassium in the absence of clinical evidence of electrolyte imbalance - simultaneous serum potassium exceeds plasma potassium by >0.4 mmol/L. We describe two patients with pseudohyperkalemia who inadvertently received inappropriate potassium binder therapy for weeks to months before the diagnosis of pseudohyperkalemia was entertained and subsequently confirmed. Potassium binders ultimately were promptly discontinued once the diagnosis of pseudohyperkalemia was confirmed. Physicians’ attention must be drawn to the availability of the new potent oral potassium binders, patiromer and sodium zirconium cyclosilicate. We strongly advocate for imperative caution with these new binders. Iatrogenic life-threatening hypokalemia remains a real concern and must be avoided. Our patients highlighted the importance of caution in the use of the newer potent potassium binders to mitigate against the causation of iatrogenic hypokalemia. Also as important is the observation that in the same patient, with changing clinical scenarios, a patient might exhibit true hyperkalemia that alternated with pseudohyperkalemia, the first of such a report.

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.

Pseudohyperkalemia and Pseudohyponatremia in Two Children with T-Cell Acute Lymphoblastic Leukemia

Pseudohyperkalemia and pseudohyponatremia are phenomena in which hematologic disorders with high cell counts result in factitious electrolyte measurements that can result in inappropriate treatment. We describe 2 children with leukemia presenting with both disturbances to highlight the importance of correlating electrolyte results from plasma with those from whole blood before intervening.

[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.

A Case of Hyperkalemia Versus Pseudohyperkalemia in Chronic Lymphocytic Leukemia

Introduction

Both hyperkalemia and pseudohyperkalemia occur in the emergency department. True hyperkalemia necessitates emergent treatment while pseudohyperkalemia requires recognition to prevent inappropriate treatment. It is imperative that the emergency physician (EP) have an understanding of the causes and clinical presentations of both phenomena.

Case Report

We present a case of an 88-year-old male with chronic lymphocytic leukemia (CLL) and suspected blast crisis who was found to have elevated serum potassium levels without other manifestations of hyperkalemia and eventually was determined to have pseudohyperkalemia due to white cell fragility.

Discussion

Differentiation of hyperkalemia and pseudohyperkalemia is a critical skill for the EP. We discuss multiple causes of hyperkalemia and pseudohyperkalemia in an effort to broaden the knowledge base.

Conclusion

We present a case of CLL as an unusual cause of pseudohyperkalemia and review common causes of pseudohyperkalemia.

Pseudohyperkalemia - Potassium released from cells due to clotting and centrifugation - a case report

Hyperkalemia is a potentially lethal condition. Pseudohyperkalemia should be always excluded before implementing treatment to prevent inappropriate cause of hypokalemia – equally a potentially lethal condition. Here we present a case report of a 62 year female with chronic myeloproliferative disorder, i.e. essential thrombocythemia. The laboratory test results for potassium concentration were 6.3 mmol/L, for platelet count 1305 x10⁹/L and for leukocyte count 39.8 x10⁹/L. This was due to a temporary drug withdrawal after a surgical intervention for gastric bleeding. Potassium concentration in lithium heparin plasma collected in a vacuum tube without gel separator and in whole blood syringe were 4.6 mmol/L and 3.4 mmol/L, respectively. It means that mechanical stress such as centrifugation can contribute to spurious hyperkalemia.
Prior to reporting unexpected hyperkalemia result, pseudohyperkalemia should always be considered by the laboratory. Such potassium results require investigation in case it is pseudohyperkalemia, which may be due to thrombocytosis and leukocytosis. In cases where thrombocytosis or leukocytosis exists, an interpretative comment indicating these conditions inserted with the results of the potassium concentration can increase awareness for more accurate patient care decisions.