A paradigmatic case of haemolysis and pseudohyperkalemia in blood gas analysis

The influence of undetected hemolysis on POCT potassium results in the emergency department

OBJECTIVES

This study aimed to evaluate discrepancies in potassium measurements between point-of-care testing (POCT) and central laboratory (CL) methods, focusing on the impact of hemolysis on these measurements and its impact in the clinical practice in the emergency department (ED).

METHODS

A retrospective analysis was conducted using data from three European university hospitals: Technische Universitat München (Germany), Hospital Universitario La Paz (Spain), and Erasmus University Medical Center (The Netherlands). The study compared POCT potassium measurements in EDs with CL measurements. Data normalization was performed in categories for potassium levels (kalemia) and hemolysis. The severity of discrepancies between POCT and CL potassium measurements was assessed using the reference change value (RCV).

RESULTS

The study identified significant discrepancies in potassium between POCT and CL methods. In comparing POCT normo- and mild hypokalemia against CL results, differences of -4.20 % and +4.88 % were noted respectively. The largest variance in the CL was a +4.14 % difference in the mild hyperkalemia category. Additionally, the RCV was calculated to quantify the severity of discrepancies between paired potassium measurements from POCT and CL methods. The overall hemolysis characteristics, as defined by the hemolysis gradient, showed considerable variation between the testing sites, significantly affecting the reliability of potassium measurements in POCT.

CONCLUSIONS

The study highlighted the challenges in achieving consistent potassium measurement results between POCT and CL methods, particularly in the presence of hemolysis. It emphasised the need for integrated hemolysis detection systems in future blood gas analysis devices to minimise discrepancies and ensure accurate POCT results.

Clinical Thresholds for Pseudohyperkalemia and Pseudonormokalemia in Patients with Thrombocytosis

BACKGROUND

The lysis of platelets during in vitro coagulation leads to increased potassium concentrations.We aimed to establish the cut-off value for platelet count interfering serum potassium and to estimate the percentage of cases of pseudohyperkalemia and pseudonormokalemia in our hospital.

MATERIALS AND METHODS

Individuals diagnosed with essential thrombocytosis (2010-2019) based on the WHO criteria for the classification of myeloid neoplasms and acute leukemia were considered.The cut-off value for the interference of platelet count on serum potassium results was calculated using the reference change value. Sensitivity and specificity were calculated using a ROC-curve, and the size of the effect by the Cohen's d.The clinical impact of both phenomena was assessed by reviewing the medical records of individuals classified as such, and also looking for potential cases in 2019 on the laboratory information system.

RESULTS

Fifty-four individuals with essential thrombocytosis were included. Potassium concentration correlated with platelet count (P-value<0.001; Spearman's ρ =0.394) in serum. The cut-off value of platelet count interfering potassium was 598x10³/μL [CI95%: 533-662x10³/μL], with an associated sensitivity and specificity of 0.67 [CI95%:0.52-0.80] and 0.58 [CI95%:0.42-0.72] respectively.The medical records of patients classified as pseudohyperkalemia or pseudonormokalemia did not include any medical action for the modification of potassium levels. In 2019, up to 0.14% of the total serum potassium determinations were susceptible to be pseudohyperkalemia or pseudonormokalemia.

CONCLUSION

This study provides a cut-off value for platelet count interfering serum potassium concentrations, and brings to light not only pseudohyperkalemia-related issues, but also the pseudonormokalemia phenomenon, which usually goes unnoticed.

Perspectives On Blood-Based Point-Of-Care Diagnostics

Background

Point of Care (POC) diagnostics are an essential component of modern medicine and are employed in a variety of clinical disciplines to improve patient outcomes and provider efficiency. Despite these benefits, there are aspects of POC testing which may still hold room for improvement. In the present study, a group of healthcare professionals familiar with different facets of blood-based POC testing provided their perspectives on the benefits and challenges of POC testing within their respective fields.

Materials and methods

The study was conducted from April to June 2019, in Colorado, United States of America. Five healthcare professionals, each working in a distinct field (anesthesiology, nursing, emergency medicine, trauma surgery, and POC management) were interviewed. Results from each of the interviews were transcribed as qualitative perspectives on POC diagnostics.

Discussion

The general consensus among participants in this study is that POC testing is tremendously beneficial, providing rapid test results, increased access to diagnostics, and improvements in hospital efficiency. However, significant challenges remain in blood-based POC diagnostics, particularly in maintaining sample quality, due to the fact that devices used for sample acquisition and handling are not designed for POC. This raises the possibility for interferents like hemolysis to occur, which may alter diagnostic results. Errors in POC diagnostics, whether due to sample, operator, or instrument error, may cause providers to lose confidence in the test. This lack of confidence can lead to duplicate testing and delayed patient diagnoses.

Conclusion

The perspectives presented in this study suggest there is a significant need for improvement in the pre-analytical phase of POC testing, and that current practice employs specimen collection technology not designed for POC. Therefore, one hypothesis is that the introduction of a collection device designed specifically for POC could reduce pre-analytical errors, standardize sample quality, improve efficiency, and further benefit patient care.