Do hemolyzed potassium specimens need to be repeated?

Hyperkalemia in a Hemolyzed Sample in Pediatric Patients: Repeat or Do Not Repeat?

OBJECTIVE

The aim of the study is to analyze whether repeat testing is necessary in healthy children presenting to a pediatric emergency department (ED) who are found to have hyperkalemia on a hemolyzed specimen.

METHODS

A 5-year retrospective analysis of pediatric ED patients found to have elevated potassium values on laboratory testing of a sample reported to be hemolyzed. All patients aged 0 to 17 years who had an elevated potassium level after an intravenous draw resulted from a serum sample that was reported as hemolyzed during an ED visit were included in the study.

RESULTS

One hundred eighty-seven patients with some degree of both hemolysis and hyperkalemia were included in the final analysis. The median age was 1.9 years of age. The most common race among all patients was White, followed by African American, and Asian. One hundred forty-five children had repeat sampling for hemolyzed hyperkalemia, 142 children, 97.9% (95% confidence interval, 95.6%-100%) had a normal potassium on repeat and 3 children, 2.1% (95% confidence interval, 0.0%-4.4%) had true hyperkalemia. The frequency of true hyperkalemia in our study population was 2% (3/145). All 3 of these patients had underlying conditions that would appropriately have raised clinician suspicion for hyperkalemia.

CONCLUSIONS

It may be unnecessary to obtain repeat samples to confirm normal potassium in a hemolyzed sample with normal blood urea nitrogen and creatinine.

Increased specimen minimum volume reduces turnaround time and hemolysis

Quantity not sufficient (QNS) specimens with minimal blood volume for testing are common in clinical laboratories. However, there is no universal definition of minimum volume for a QNS specimen and little data is available addressing the impact of QNS / low volume specimens on turnaround time (TAT) and sample hemolysis. We compared the TAT and hemolysis index from samples ≤1.0 mL to all specimens received and quantified the number of specimens with reduced blood volume. A new QNS policy requiring ≥1.5 mL of sample in a blood tube for laboratory analysis was implemented and the results were assessed by sample hemolysis and TAT. The median laboratory TAT for samples with ≤1.0 mL of blood was 61 min (Interquartile Range, IQR: 50-82), in contrast to 28 min (26-34) for all samples. The hemolysis index for samples ≤1.0 mL was 112 (65-253) and 15 (8-29) for all samples. Requirement of a minimum volume of 1.5 mL of blood resulted in the proportion of samples with TAT ≥ 60 min to decrease from 10.4% to 4.24% in the ED, and for specimens cancelled due to hemolysis to decrease from 4.24% to 3.38%. This policy was introduced hospital wide with similar effects. Together, we correlate limited specimen volume with an increase in laboratory TAT and hemolysis. Implementation of a QNS policy of ≥1.5 mL and provider education provided a significant and durable reduction in TAT and specimen hemolysis.

Accuracy of Hemolyzed Potassium Levels in the Emergency Department

Introduction

In the emergency department (ED), pseudohyperkalemia from hemolysis may indirectly harm patients by exposing them to increased length of stay, cost, and repeat blood draws. The need to repeat hemolyzed potassium specimens in low-risk patients has not been well studied. Our objective was to determine the rate of true hyperkalemia among low-risk, adult ED patients with hemolyzed potassium specimens.

Methods

We conducted this prospective observational study at two large (129,000 annual visits) academic EDs in the mid-Atlantic. Data were collected from June 2017–November 2017 as baseline data for planned departmental quality improvement and again from June 2018–November 2018. Inclusion criteria were an initial basic metabolic panel in the ED with a hemolyzed potassium level > 5.1 milliequivalents per liter that was repeated within 12 hours, age (≥18, and bicarbonate (HCO₃) > 20. Exclusion criteria were age > 65, glomerular filtration rate (GFR) < 60, creatine phosphokinase > 500, hematologic malignancy, taking potassium-sparing or angiotensin-acting agents, or treatment with potassium-lowering agents (albuterol, insulin, HCO₃, sodium polystyrene sulfonate, or potassium-excreting diuretic) prior to the repeat lab draw.

Results

Of 399 encounters with a hemolyzed, elevated potassium level in patients with GFR ≥ 60 and age > 18 that were repeated, we excluded 333 patients for age > 64, lab repeat > 12 hours, invalid identifiers, potassium-elevating or lowering medicines or hematologic malignancies.This left 66 encounters for review. There were no instances of hyperkalemia on the repeated, non-hemolyzed potassium levels, correlating to a true positive rate of 0% (95% confidence interval 0–6%). Median patient age was 46 (interquartile range [IQR] 34 – 56) years. Median hemolyzed potassium level was 5.8 (IQR 5.6 – 6.15) millimoles per liter (mmol/L), and median repeated potassium level was 3.9 (IQR 3.6 – 4.3) mmol/L. Median time between lab draws was 145 (IQR 87 – 262) minutes.

Conclusion

Of 66 patients who met our criteria, all had repeat non-hemolyzed potassiums within normal limits. The median of 145 minutes between lab draws suggests an opportunity to decrease the length of stay for these patients. Our results suggest that in adult patients < 65 with normal renal function, no hematologic malignancy, and not on a potassium-elevating medication, there is little to no risk of true hyperkalemia. Further studies should be done with a larger patient population and multicenter trials.

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.

Prevalence and factors associated with false hyperkalaemia in Asians in primary care: a cross-sectional study (the Unlysed Hyperkalaemia- the Unseen Burden (UHUB) study)

Serum potassium is part of routine laboratory tests done for patients with hypertension or diabetes mellitus in primary care. Those found to have raised potassium (K>5.5 mmol/L) are recalled for repeat potassium in emergency departments or primary care clinics. Repeat potassium are often normal (≤5.5 mmo/L), that is, false hyperkalaemia. Haemolysis is known to cause false hyperkalaemia. We postulated that unlysed false hyperkalamia was prevalent and was associated with factors such as delayed processing time.

OBJECTIVE

We aimed to determine the prevalence of unlysed false hyperkalaemia and the factors associated with false-and-true-hyperkalaemia.

SETTING

Outpatients in a cluster of public primary care clinics (polyclinics) in Singapore.

PARTICIPANTS

All patients of any ethnicity aged ≥21 with serum potassium test done.

METHODS

Electronic health records of index patients with potassium >5.5 mmol/L and its corresponding laboratory processing time in seven local polyclinics were reviewed between August 2015 and August 2017. Haemolysed specimens and patients on sodium polystyrene sulfonate (SPS) suspension were excluded. If repeat potassium level was ≤5.5 mmol/L within 8 days, the case was defined as false hyperkalaemia. The proportion of such patients was computed to determine its prevalence. Linear and logistic regressions were used to identify the associated factors.

RESULTS

The study population comprised of 3014 index cases, of which 1575 had repeat potassium tests without preceding SPS. 86.4% (1362/1575) of them had potassium ≤5.5 mmol/L. The average processing time among specimens with potassium ≥6.0 mmol/L was 50 min longer, compared with those with potassium <5.1 mmol/L. Risk factors significantly associated with false hyperkalaemia included estimated glomerular filtration rate (eGFR) (60-89 mL/min/1.73 m², OR=3.25, p<0.001;>90 mL/min/1.73 m², OR=3.77, p<0.001) and delayed laboratory processing time (beta coefficient 0.001, p<0.001).

CONCLUSION

The prevalence of false hyperkalaemia was 86.4%. Recommendation to repeat potassium tests may target those with eGFR<60ml/min/1.73m².

Preliminary study on the correlation of plasma hemolysis index and potassium measurement of inpatient in the Biochemistry Laboratory of General Hospital Kuala Lumpur

Background: Potassium (K+) is the essential micronutrient and major intracellular fluid cation which involves in various cellular metabolism activities, maintaining fluid and electrolyte balance. Measurement of blood concentration in a medical laboratory has often encountered disturbances such as hemolysis, which may lead to the elevation in measurement and affects the medical diagnosis and treatment of the patient, conceivably fatal. Hemolysis can be decided using hemolysis index (H-index) through automation. Methods: In this study, H-index and concentration of fifty hospitalized patients (n=50) hemolysed blood samples were measured and correlated. Freezing-and-thaw method was used to hemolyse the blood samples. Different concentrations were diluted and analyzed using COBAS 8000 biochemistry analyser. Data were collected and analyzed using SPSS version 25. Results: Our findings showed significant mean differences, 0.001 (p ≤ 0.05) and strong positive linear relationship between two variables (H-index and ) (r=0.764, p ≤ 0.05). By applying calculated linear equation [y = 0.0048x + 5.146, = 0.5838], critical value of 6.0 mmol/l gives H-index of 178, H-index above 178 is suggested to be critical. Discussion and Conclusion: concentration increases in proportion to H-index. A greater degree of hemolysis causes more ions to be released into extracellular fluid, respectively. In conclusion, when H-index less than 178 in measurement and there is no analytical significance bias generated, the result is acceptable, whilst H-index with analyte variation between clinically significant bias range can be released with a comment regarding the potential of data alteration. Meanwhile, result with H-index exceeding the cut-offs should be suppressed and recollection of sample is required.

Manual versus Pump Infusion of Distending Media for Hysteroscopic Procedures: A Randomized Controlled Trial

Fluid overload is a potential complication of hysteroscopic procedures with the possibility of dangerous electrolyte changes. This prospective randomized controlled trial aimed to compare perioperative outcomes and changes in electrolytes after hysteroscopic procedures between the manual infusion (MI) and the pump infusion (PI) methods for distending media infusion. One hundred consecutive women who had hysteroscopic procedures between December 2013 and February 2017 were recruited and randomly allocated to either the MI or PI group. The PI group was associated with an increased volume of infused fluid and collected fluid compared with the volumes of the MI group. Almost all serum electrolyte levels differed significantly between the baseline and postoperative values in both groups; however, no significant differences were noted between the groups. The change in potassium level was positively correlated with the volume of fluid deficit (Spearman's rho = 0.24, P = 0.03), whereas the change in calcium level was negatively correlated with the volume of fluid deficit (Spearman's rho = -0.26, P = 0.046). With no between-group differences in the changes in the other perioperative parameters and electrolytes, the MI method can be a good alternative for delivering distending media for hysteroscopic procedures.

Potassium homoeostasis and pathophysiology of hyperkalaemia

Determination of potassium level is one of the most frequent laboratory tests in clinical medicine. Hyperkalaemia is defined as a potassium level >5.0 mmol/L and is one of the most clinically important electrolyte abnormalities, because it may cause dangerous cardiac arrhythmia and sudden cardiac death. Here, we review methodological challenges in the determination of potassium levels, important clinical aspects of the potassium homoeostasis as well as of the pathophysiology of hyperkalaemia.