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.

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.

Prevalence and management of hyperkalemia in chronic kidney disease and heart failure patients in the Gulf Cooperation Council (GCC)

Hyperkalemia is a frequent complication in patients with chronic kidney disease (CKD) or heart failure (HF) and associated with neuromuscular manifestations, changes in the electrocardiogram, and increased risk of mortality. While data on the prevalence and management of hyperkalemia in the gulf region are scarce, risk factors such as preference for potassium-rich foods (e.g., dates and dried fruits/vegetables), periods of intense fasting (e.g., Ramadan), and diabetes (an ancestor of CKD and HF) are common. Therefore, a panel of nephrologists and cardiologists from countries of the Gulf Cooperation Council (GCC) convened to collate and review available data on the prevalence, regional drivers, and current practice in the management of hyperkalemia in the region. Eventually, this review provides consensus recommendations on a balanced utilization of dietary and pharmacological options including new potassium binders for achieving and sustainably maintaining desirable serum potassium levels in countries of the GCC region. Alignment with regional habits and practice was a key aspect to facilitate the uptake of the recommendations into physicians' practice and patients' lives.

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.

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.

Assessing Safety of Pneumatic Tube System (PTS) for Patients with Very Low Hematologic Parameters

Background

Preventive interventions save lives during the process of chemotherapy for hematologic malignancies, when a hematology laboratory can ensure accurate results. The use of a pneumatic tube system (PTS) is associated with measurement errors and unnecessary transfusions. The aim of this study was to evaluate pre-analytical errors associated with transportation method (PTS versus hand-delivered) and to investigate whether there are unnecessary transfusion events in pancytopenia leukemia patients with very low hematological parameters.

Material/Methods

A total of 140 paired blood collections were performed for hemogram and biochemistry assays. Paired EDTA and serum gel blood samples were collected from 58 cases with acute leukemia on different days. For each pair, one sample was hand-delivered by a courier (Group 1) while the other sample was transported through a PTS (Group 2).

Results

The hand-delivered method showed that some platelet transfusions were unnecessary for different thrombocyte cut-off values. Calculated unnecessary platelet (PLT) transfusion ratios when using PTS (PLT <30×10³/μL, 16.3%; PLT <25×10³/μL, 16.4%; PLT <20×10³/μL, 80.3%; PLT <15×10³/μL, 48.6%; and PLT <10×10³/μL, 150.0%) were found to be statistically significant (p=0.002, p=0.046, p<0.000, p=0.028, and p<0.000, respectively). In contrast, for RBC transfusion ratios, although the ratios were high in Group 2, we found no significant difference between the two groups; (HGB <8.0 g/dL, 23.3%; HGB <9.0 g/dL, 25.0%, HGB<10.0 g/dL, 19.3%) and (p=0.002, p=0.085, p<0.160, and p=0.235, respectively).

Conclusions

Although our results cannot be universally applied, physicians should be careful, skeptical, and suspicious of transfusion decisions in hematology clinics and consider potential analytical and pre-analytical errors in cases of severe cytopenia when using PTS.

Gentle blood aspiration and tube cushioning reduce pneumatic tube system interference in lactate dehydrogenase assays

Background

Use of a hospital pneumatic tube system may be associated with measurement errors.

Methods

A venous blood sample was collected from 79 patients into a pair of lithium heparin tubes; one tube was sent to the laboratory by porter and the other was sent via the pneumatic tube system. Plasma lactate dehydrogenase concentrations were then assayed.

Results

Lactate dehydrogenase concentrations were overestimated (median bias: 18.8%) when evacuated vacuum lithium heparin tubes were sent by pneumatic tube system. This bias was reduced by bubble-wrapping the standard lithium heparin tube or using Monovette lithium heparin tubes in aspiration mode (median bias: +8.7% and −0.3%, respectively).

Conclusions

Cushioning and aspiration-mode sampling may limit pneumatic tube system-associated overestimation of lactate dehydrogenase concentrations.