A-345 Effect of Hemolysis on Routine Blood Gas Analytes

Abstract

Background Hemolysis is a major pre-analytical concern for most laboratory analytes. Detection of hemolysis and mitigation efforts are especially important for analytes, such as potassium, with high intracellular concentrations. Routine serum and plasma chemistry tests are performed on analyzers with the capacity to detect and measure the degree of hemolysis. However, for whole blood chemistries and blood gas measurements, the instruments utilized lack this capacity. The aim of this study was to evaluate the effect of hemolysis on whole blood and blood gas analytes and to compare visual assessments of hemolysis to measured hemolysis indices (H-index). Methods Remnant whole blood samples were split into two portions and each portion was aspirated and dispensed through a syringe one or more times. For the mock portion, only the syringe was used, while the hemolyzed portion had a needle affixed to the end of the syringe. The needle provided shear stress on the red blood cells to induce hemolysis, while the mock procedure was used to assess the impact of aspirating/dispensing on the sample in the absence of hemolysis. Each portion was then analyzed on a Radiometer ABL800 series instrument, spun down, and the H-index of the plasma portion was measured on a Roche cobas 8000 instrument. Medical technologists recorded their visual assessment of the specimens, with two technologists agreeing to the categorization of the specimen as either slightly, moderately, or severely hemolyzed. Degree of hemolysis was categorized by the delta (hemolyzed - mock) of the measured H-index: slight hemolysis was defined as an H-index delta of <100, moderate as 100-500 and severe as >500. Results The effect of hemolysis, with H-indices ranging from 2 to 3861, on 13 routine blood gas analytes was studied for 85 whole blood specimens. Hemolysis had little effect on metabolites, as percent bias was within ±3% at all levels of hemolysis for glucose, creatinine, and lactate. Similarly, most cooximetry components were minimally affected, with total hemoglobin, oxyhemoglobin, carboxyhemoglobin, and oxygen saturation within ±5% bias at all levels of hemolysis. Methemoglobin had a larger overall negative bias, with slight, moderate, and severe hemolysis levels yielding percent biases of -6.6, -12.3, and -13.3%, respectively. As expected, potassium displayed a significant positive bias with increasing hemolysis, with a generally linear trend. At moderate levels of hemolysis, the average potassium bias was 24.0% and at severe levels, over 100%. Sodium and ionized calcium also displayed overall linear trends but with a negative bias. At slight, moderate, and severe levels of hemolysis, sodium had a -0.56, -1.10, and -3.96% bias, and ionized calcium had a -2.99, -5.65, and -15.5% bias respectively. Conclusions Hemolysis can falsely increase or decrease a range of blood gas analytes and lead to misinterpretation of results and adversely affect clinical decision-making. Therefore, equipping current blood gas analyzers with hemolysis detection capabilities is crucial to enable laboratories to mitigate this effect and ensure accurate results for patient care.