DIAGNOSTICS
Pre-analytical errors: how to detect and interpret HIL interference
In diagnostic testing errors can occur at any stage of testing, with pre-analytical interference from haemolysis, icterus, and lipaemia (HIL) being particularly common. HIL interference can lead to inaccurate results and is therefore a major concern for clinical laboratories. Jason Armstrong explores the causes and effects of HIL interference and discuss strategies for its detection and mitigation in clinical laboratory analysis.
Errors can occur at any stage in the pre- analytical, analytical, or post-analytical stage of a diagnostic test. It is general practice for errors in the analytical stage to be identified through quality control procedures. However, pre-analytical errors are often treated with less importance than those in later stages of testing. Interference caused by haemolysis, icterus and lipaemia (HIL) are common forms of pre-analytical error which affect assay methods, yielding erroneous results. HIL interference is not novel and has been historically identified through a series of visual assessments.
While haemolytic, icteric and lipaemic interference causes a visual change in the sample, these methods are not quantitative and are subject to interpretation by laboratory professionals. Modern analysers have built-in capabilities for the automated detection of HIL interference which can quantitatively or semi-quantitatively measure haemolysis, icterus and lipaemia, and provide and an index for each. This data can then be used to determine if a sample should be accepted for testing or rejected due to intrinsic interference.
Haemolysis Around 30% of samples received from emergency rooms are subject to haemolysis and therefore, are rejected for testing.1
Haemolytic interference
occurs as a result of degradation of red blood cells due to tangential stress which causes a denaturation of the membrane and the release of erythrocyte components. This is commonly due to poor sample collection technique, poor sample storage, or inadequate sample transportation.2
Haemolysis can cause
interference through various mechanisms, the most common is the presence of erythrocyte intracellular components, due to the degradation of cells, which are detected by assays and result in falsely high results in those analytes
2.0 2.5 3.0
0.0 0.5 1.0 1.5
Haemolysis
already present in high concentrations within the cell and falsely low results for analytes of low intracellular concentration. Additionally, erythrocyte components such as haemoglobin, potassium ions, and aspartate aminotransferase can cause degradation to some analytes such insulin and troponin T.1
measured at 340-440nm and 540- 580nm3
greatest absorbance at 415nm,1
Haemolysis is likely to affect assays as haemoglobin exhibits its
causing
interference in diagnostic tests such as those for iron, lipase and albumin.1
Icterus
Lipaemia 300 350 400 450 500 550 Wavelength (Nm)
A graph displaying wavelengths at which interference caused by haemolysis, icterus and lipaemia are likely to be evident.
WWW.PATHOLOGYINPRACTICE.COM JUNE 2023 49 600 650 700 750
Absorbance
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