Lipemia: causes, interference mechanisms, detection and management

Abstract

In the clinical laboratory setting, interferences can be a significant source of laboratory errors with potential to cause serious harm for the patient. After hemolysis, lipemia is the most frequent endogenous interference that can influence results of various laboratory methods by several mechanisms. The most common preanalytical cause of lipemic samples is inadequate time of blood sampling after the meal or parenteral administration of synthetic lipid emulsions. Although the best way of detecting the degree of lipemia is measuring lipemic index on analytical platforms, laboratory experts should be aware of its problems, like false positive results and lack of standardization between manufacturers. Unlike for other interferences, lipemia can be removed and measurement can be done in a clear sample. However, a protocol for removing lipids from the sample has to be chosen carefully, since it is dependent on the analytes that have to be determined. Investigation of lipemia interference is an obligation of manufacturers of laboratory reagents; however, several literature findings report lack of verification of the declared data. Moreover, the acceptance criteria currently used by the most manufacturers are not based on biological variation and need to be revised. Written procedures for detection of lipemia, removing lipemia interference and reporting results from lipemic samples should be available to laboratory staff in order to standardize the procedure, reduce errors and increase patient safety.

Keywords: biological variation; interference testing; laboratory error; lipemia interference; preanalytical phase.

Figure 1.

Lipoprotein particle sizes and lipemia. Lipoproteins that are coloured dark grey cause turbidity of the sample. VLDL – very low density lipoproteins (L – large; M - medium; S – small), LDL - low density lipoproteins; HDL - high density lipoproteins.

Figure 2.

Interferogram – a graphical presentation of interference. Figure presents measurement of interference for three different reagents (Reagent 1, Reagent 2 and Reagent 3). Increasing concentrations of interferent are presented on x-axis, and measured bias on y-axis. Dashed lines present criteria of acceptance. A point where the full line intercepts the dashed line is highest accepted concentration of interferent.

Figure 3.

Flowchart for management of lipemic samples.