Does the use of fish oil-based lipid emulsion in the clinical setting of total parenteral nutrition and lipid rescue therapy interfere with common laboratory analytes on Roche Cobas 6000?

Abstract

Background Lipaemic interference on automated analysers has been widely studied using soy-based emulsion such as Intralipid. Due to the greater adoption of fish oil-based lipid emulsion for total parenteral nutrition in view of improved clinical outcomes, we seek to characterize the optical properties of SMOFlipid 20% (Fresenius Kabi, Bad Homburg, Germany), a fish oil-based emulsion, on the Roche Cobas 6000 chemistry analyser (Roche Diagnostic, Basel, Switzerland). Method Various amounts of SMOFlipid were spiked into pooled serums. We plotted Roche Cobas Serum Index Gen.2 Lipaemia Index (L-index) against the amount of SMOFlipid added. We then studied the interference thresholds for aspartate aminotransferase, alanine aminotransferase, albumin and renal panel analytes using SMOFlipid. We subjected five levels of spiked lipaemia to high-speed centrifugation and analysed the specimens pre- and post-centrifugation. To postulate whether fish oil-based lipid emulsion interferes with laboratory results in the clinical setting, we calculated concentrations of SMOFlipid post-lipid rescue therapy and steady-state concentration of a typical total parenteral nutrition regime using pharmacokinetic principles. Results SMOFlipid optical behaviour is similar to Intralipid using the Serum Index Gen.2 L-index, with 1 mg/dL of SMOFlipid representing 1 unit of L-index. Manufacturer-stated interference thresholds are accurate for alanine aminotransferase, aspartate aminotransferase, albumin, urea and creatinine. High-speed centrifugation at 60 min 21,100 g facilitates the removal of fish oil-based SMOFlipid. Conclusion Based on the interference thresholds we verified and pharmacokinetics parameters provided by SMOFlipid manufacturer, total parenteral nutrition may not interfere with chemistry analytes given sufficient clearance, but lipid rescue therapy will interfere. Further studies assessing lipaemic interference on immunoassays are needed.

Authors’ reply to ‘Plasma clearance and lipaemic index of lipid emulsion used for lipid emulsion treatment’

“…1 Indeed, we have accounted for the clearance of lipaemia for physiological doses of total parenteral nutrition in our article. 2 We agree that lipid rescue therapy is effective in the management of cardiovascular collapse from overdose of lipophilic drugs (e.g. calcium channel blockers, tricyclic antidepressants) and local anaesthetic systemic toxicity (LAST), which was one of our motivations for performing the interference experiments.…”

“…1 Interference is most likely to occur if the paraprotein is an IgM type, due to its large pentameric structure, although IgA interference has also been reported. 2 We aimed to determine the prevalence and extent of paraprotein interference using three commonly measured analytes (bilirubin, creatinine, and phosphate) which have been previously reported to suffer from assay interference.…”

Plasma clearance and lipaemic index of lipid emulsion used for lipid emulsion treatment

“…I read with interest the article entitled ‘Does the use of fish-oil based lipid emulsion in the clinical setting of total parenteral nutrition (TPN) and lipid rescue therapy interfere with common laboratory analytes on Roche Cobas 6000?’ recently published in the Annals of Clinical Biochemistry . 1 Tan and Wong describe that initial administration alone (1.5 mL/kg, 20% SMOFlipid emulsion) followed by 15 mL/kg/h for 5 min, pharmacokinetically produced a lipaemic index of 660 (660 mg/dL) and 1220 (1220 mg/dL), respectively, causing interference with aspartate aminotransferase and alanine aminotransferase measurements, on account of exceeding the lipaemic threshold for these assays. 1 However, the in vivo plasma clearance of lipid emulsion will also affect the plasma concentration of lipid emulsion.…”

“…1 Tan and Wong describe that initial administration alone (1.5 mL/kg, 20% SMOFlipid emulsion) followed by 15 mL/kg/h for 5 min, pharmacokinetically produced a lipaemic index of 660 (660 mg/dL) and 1220 (1220 mg/dL), respectively, causing interference with aspartate aminotransferase and alanine aminotransferase measurements, on account of exceeding the lipaemic threshold for these assays. 1 However, the in vivo plasma clearance of lipid emulsion will also affect the plasma concentration of lipid emulsion. Lipid emulsion, containing triglyceride, bypasses the gastrointestinal tract and directly enters the blood stream.…”

“…5 The lipaemic index of SMOFlipid described in this study would be expected to decrease relatively quickly after discontinuation of infusion of SMOFlipid. 1…”