Clinical utility of the lipemic index for identifying severe triglyceride-rich lipoprotein disorders in adults undergoing routine blood testing.

BACKGROUND

The lipemic index (L-index) is an automated measure of plasma turbidity used for pre-analytical quality control in clinical chemistry. As turbidity often reflects accumulation of triglyceride-rich lipoproteins (TRL), elevated L-index values may indicate underlying hyperlipoproteinemias, including severe hypertriglyceridemia and familial dysbetalipoproteinemia (FD). These rare, underdiagnosed disorders can have severe clinical consequences such as pancreatitis and cardiovascular disease.

OBJECTIVE

This study evaluated the clinical utility of the L-index for identifying severe TRL disorders in adults undergoing routine blood testing.

METHODS

In this cross-sectional study, all samples with an L-index result were eligible, except pediatric and ICU samples. In patients with L-index ≥1, a lipid panel and apoB were measured in leftover material. After excluding patients receiving intravenous lipid emulsions, patients with dyslipidemia were screened for severe TRL disorders (severe hypertriglyceridemia [>10 mmol/L] or an FD-like phenotype [TG ≥2.0 mmol/L, TC ≥5.2 mmol/L and non-HDL-C/apoB >3.69]). FD-like phenotypes were assessed using polyacrylamide gradient gel electrophoresis (PGGE).

RESULTS

Among 332,476 consecutive samples from 71,768 unique patients, 575 patients (0.8%) had L-index ≥1, of whom 441 (77%) had dyslipidemia. Among patients with L-index ≥1 and dyslipidemia, 154/441 (35%) met biochemical screening criteria for a severe TRL disorder. PGGE confirmed an FD-like phenotype in 2/20 (10%) cases.

CONCLUSION

Although the prevalence of an elevated L-index was low, approximately one-third of patients with L-index ≥1 and dyslipidemia met biochemical screening criteria for a severe TRL disorder. As an automated measure available at no additional cost, the L-index may help identify patients warranting further evaluation, particularly for severe hypertriglyceridemia and potentially FD-like phenotypes.