Estimation of lipemia interference with automated HIL-test on d-dimer ACL TOP 50 series analysis - reveals a higher cut-off than manufacturer's recommendations.

Fibrin-d-dimer (d-dimer) is essential for the diagnosis and treatment of thrombosis patients. The new ACL TOP 50- series used for d-dimer determination, integrates a preanalytical interference check for hemolysis, icterus and lipemia (HIL-test). Using earlier versions of ACL TOP, HIL was evaluated by visual inspection by the biomedical laboratory scientist. With the new integrated HIL-test, lipemia is determined by measuring turbidity in the sample at 671 nm, reflecting the lipid content in the sample. Using the new ACL TOP 50- series, we observed more samples being rejected for d-dimer analysis due to lipemia-interference evaluated by the integrated HIL-test suggesting a discrepancy between the former triglyceride-based cut-off and the new turbidity-based cut-off. Therefore, to re-evaluate the lipemia interference cut-off with the turbidimetric measurement, we did a spike-in experiment, using intralipid as lipemia simulation. Three × six different patient pools were prepared from sodium-citrate plasma. We observed no interference in the d-dimer assay by intralipid concentrations resulting in milli absorbances (mAbs) below 3000 mAbs. Thus, the cut-off for lipemia interference using the integrated HIL-test on ACL TOP 550 should be 3000 mAbs. This cut-off will reduce the number of samples rejected due to false positive interference and at the same time reduce 'hands on' time for the biomedical laboratory scientists and minimize the risk of subjective evaluation by a visual inspection.