A-190 The Effect of Lipemia on the Laboratory Assessment of Blood Gases

Abstract

Abstract Background Unlike the electrolyte exclusion phenomenon, little is known about the effects of lipemia on the laboratory assessment of total carbon dioxide (tCO2) and bicarbonate (HCO3−). Depending on the method used, lipemia-induced turbidity of a specimen can impact the outcome of the results. The photometric-enzymatic, rather than the indirect ion selective method is more easily interfered with by a turbid sample. Consequently, HCO3− and tCO2 results from a severely lipemic sample may be falsely diminished. A recent case report suggests an association between high lipids and HCO3−. A larger study to investigate this trend is imperative to guide laboratory and medical practice, since preanalytical component accounts for approximately 68% of all clinical laboratory errors. This study aims to investigate the analytical relationship between lipemia and blood gases analyses. Methodology Three months’ worth of patient test results totaling 660 data points were retrospectively extracted from the electronic health record and filtered using an excel spreadsheet. Data collected included patient results of triglycerides (TGs), total cholesterol (tChol), HDL-Cholesterol as well as tCO2 (using enzymatic method), HCO3−, pH and pCO2 from both ambulatory and in-patient setting. The data was analyzed using excel spreadsheet and GraphPad prism. Results 399 patients had TGs results, 372 had tCO2, and 162 had TGs and tCO2 simultaneously resulted. Of the 372 tCO2 measurements, 79 had lower than the reference interval and 87 were simultaneously performed with pH and TGs, out of which 22 had low tCO2, unextreme TGs (<1000 mg/dL) and low pH; only 2 had low tCO2, unextreme TGs and normal pH; 1 patient had low tCO2, high TGs (>1000 mg/dL) and low pH and 4 patients had low tCO2, high TGs and normal pH. All low HDL-C measurements also had low tCO2 and high TGs. Of the 31 patients who had TGs above 1000 mg/dL, 20 had normal tCO2 while 11 recorded low tCO2 and none had high tCO2; 3 had low tCO2 and low pH and, no patient recorded normal tCO2 and low pH, 4 had low tCO2 and normal pH of which 3 had TGs > 4000 mg/dL. In all 5 instances of high initial TGs with low tCO2 measurements, tCO2 continually increased as the high TGs were being serially resolved. Discussion and Conclusion Overall, our data shows an inverse correlation between extremely high TGs > 4000 mg/dL and tCO2 which in the presence of normal pH, rules out metabolic disturbance. Since tCO2 chiefly represents HCO3-, low tCO2 in the setting of low pH and unextreme TG, indicates metabolic acidosis. The serial increase in tCO2 as the extremely high TGs are resolved corroborates this converse correlation. The present data demonstrates that resolution of the lipemic sample is essential not only for the accuracy of electrolytes results, but also to improve the interpretation of blood-gas results. The outcome of this study is beneficial for minimization of preanalytical interferences, quality improvement of laboratory process and the improvement of the management of patients suspected with metabolic abnormalities. In the future, an expanded data set and interventional studies will be explored to further authenticate our present understanding.