Intravenous lipid emulsion interference in coagulation testing: an ex vivo analysis.

Introduction: Intravenous lipid emulsion is used in the rescue treatment of certain poisonings. A complication is interference with laboratory analyses. The aim of this study was to determine the impact of intravenous lipid emulsion on routine laboratory analysis of coagulation parameters ex vivo and determine if any of the analytical techniques remain reliable.

Methods: Samples were obtained from 19 healthy volunteers and divided in triplicate. One sample served as a control, and the other two were diluted to simulate the treatment of an average adult with Intralipid^® 20 per cent Fresenius Kabi 100 mL (dilution-1) or 500 mL (dilution-2). Coagulation tests performed were prothrombin time, activated prothrombin time, D-dimer concentration and fibrinogen. Coagulation testing was performed by three techniques. Test-1 was performed on a Sysmex CN6000 analyzer. Test-2 was performed with a manual mechanical endpoint method using the semi-automated Stago KC4 Delta. Test-3 involved high-speed centrifugation before repeat testing on the Sysmex CN6000 analyzer.

Results: For test-1, only nine (47 per cent) samples in dilution-1 could be analyzed for coagulation tests, and no coagulation tests could be analyzed for dilution-2 because of lipaemia. For test-2 and test-3, all samples could be analyzed, and all results of both testing methods fell within the limits of the laboratory reference range.

Discussion: Difficulties in laboratory analysis of patients having received intravenous lipid emulsion are due to multiple factors. Most automated coagulation analyzers use optical measurements, which can be unreliable in the presence of a high intravenous lipid concentration. By altering the lipaemia in the testing solution using high-speed centrifugation or by using manual mechanical endpoint detection, we were able to obtain reliable results. These findings are limited by the use of an ex vivo method and healthy volunteers.

Conclusions: This ex vivo model confirms that Intralipid^® interferes with routine coagulation studies. It is important that clinicians are aware and inform their laboratories of its administration.