Performance of electrolyte measurements assessed by a trueness verification program

Electrolyte measurements are essential for diagnosing and monitoring various clinical conditions. However, ensuring consistency and accuracy across laboratories remains a challenge. Prior research has shown that biological variation can guide acceptable performance limits. Despite this, no prior work had resolved how real-world laboratory systems perform against these limits. This gap motivated a need to assess laboratory performance using commutable samples and reference methods. Standardization efforts often rely on external quality assessment programs, but the impact of system homogeneity on accuracy is not well understood. Laboratories may use different combinations of instruments, reagents, and calibrators, leading to variability. This uncertainty drove the need for a study to evaluate the effects of system homogeneity on electrolyte measurement performance. No prior work had resolved the comparative performance of homogeneous versus non-homogeneous systems in this context. This study aimed to fill that gap by analyzing data from a national trueness verification program.

The study aimed to evaluate the performance of electrolyte measurements in Chinese clinical laboratories using a trueness verification program. The goal was to assess how well laboratories met performance criteria based on biological variation. The focus was on four key electrolytes: sodium, potassium, calcium, and magnesium. These electrolytes are frequently measured but can vary significantly between laboratories. The researchers wanted to determine whether system homogeneity influenced measurement accuracy. They also aimed to compare the performance of homogeneous and non-homogeneous systems. The motivation stemmed from the need to improve standardization and reduce variability in electrolyte testing. By analyzing data from 187 laboratories, the study aimed to provide insights into current performance levels and identify areas for improvement. This approach allowed for a comprehensive evaluation of precision, trueness, and total error.

Frozen sera with known commutability were distributed to 187 clinical laboratories in China. Each laboratory measured four electrolytes: sodium, potassium, calcium, and magnesium. Target values were assigned by two reference laboratories using reference methods. The study evaluated three performance metrics: precision (CV), trueness (bias), and total error (TEa). Biological variation was used to derive tolerance limits for each metric. The researchers compared the performance of homogeneous and non-homogeneous systems. Homogeneous systems used the same manufacturer for instrument, reagent, and calibrator. Non-homogeneous systems used different manufacturers for at least one component. The study aimed to determine whether system homogeneity affected the ability to meet performance criteria. This approach allowed for a direct comparison of system types and their impact on measurement accuracy.

Approximately half of the laboratories used a homogeneous system for calcium and magnesium measurements. Over 80% used a homogeneous system for sodium and potassium. More laboratories met the imprecision tolerance limit (CVa) than the trueness (biasa) or total error (TEa) limits. For sodium, calcium, and magnesium, pass rates for total error were similar to those for bias, with both below 50%. For potassium, pass rates for CV and TE exceeded 90%. Homogeneous systems outperformed non-homogeneous systems for all three quality specifications. The minimal performance criteria for sodium, calcium, and magnesium were based on biological variation. The use of commutable PT/EQA samples with reference-assigned values helped monitor performance. These findings suggest that system homogeneity is a key factor in achieving better measurement accuracy.

The study found that homogeneous systems for electrolyte measurement outperformed non-homogeneous systems in terms of precision, trueness, and total error. The researchers propose that system homogeneity contributes to better performance. The use of commutable PT/EQA samples with reference-assigned values is essential for monitoring and improving laboratory performance. For sodium, calcium, and magnesium, the pass rates for total error were similar to those for bias, indicating a need for improvement in accuracy. For potassium, the pass rates for CV and TE were higher, suggesting better performance. The authors suggest that calibrator accuracy and assay stability remain challenges in achieving optimal performance. The findings highlight the importance of using reference methods for assigning values in PT/EQA programs. These results support the use of homogeneous systems to enhance the reliability of electrolyte measurements.