Discordance between apolipoprotein B and low-density lipoprotein particle number is associated with insulin resistance in clinical practice

- Discordance between apolipoprotein B (apoB) and low-density lipoprotein (LDL) particle number by nuclear magnetic resonance spectroscopy in routine clinical practice is more widespread than currently recognized.
- In a large cohort of patients (N = 412,013), discordance (LDL particle concentration [LDL-P] > ApoB) was associated with smaller LDL particle sizes and hyperinsulinemia, whereas discordance (ApoB > LDL-P) was associated with elevated levels of lipoprotein (a).
- In a smaller group of well-characterized patients (N = 1411), similar patterns were observed, and discordance (LDL-P > ApoB) was also associated with higher rates of statin use.

BackgroundDiscordance between measures of atherogenic lipoprotein particle number (apolipoprotein B [ApoB] and low-density lipoprotein [LDL] particle number by nuclear magnetic resonance spectroscopy [LDL-PNMR]) is not well understood. Appropriate treatment considerations in such cases are unclear.ObjectivesTo assess discordance between apoB determined by immunoassay and LDL-PNMR in routine clinical practice, and to characterize biomarker profiles and other clinical characteristics of patients identified as discordant.MethodsTwo retrospective cohorts were evaluated. First, 412,013 patients with laboratory testing performed by Health Diagnostic Laboratory, Inc., as part of routine care; and second, 1411 consecutive patients presenting for risk assessment/reduction at 6 US outpatient clinics. Discordance was quantified as a percentile difference (LDL-PNMR percentile − apoB percentile) and attainment of percentile cutpoints (LDL-PNMR ≥ 1073 nmol/L or apoB ≥ 69 mg/dL). A wide range of cardiovascular risk factors were compared.ResultsApoB and LDL-PNMR values were highly correlated (R2 = 0.79), although substantial discordance was observed. Similar numbers of patients were identified as at-risk by LDL-PNMR when apoB levels were < 69 mg/dL (5%-6%) and by apoB values when LDL-PNMR was < 1073 nmol/L (6%-7%). Discordance (LDL-PNMR > apoB) was associated with insulin resistance, smaller LDL particle size, increased systemic inflammation, and low circulating levels of “traditional” lipids, whereas discordance (apoB > LDL-PNMR) was associated with larger LDL particle size, and elevated levels of lipoprotein(a) and lipoprotein-associated phospholipase A2 (Lp-PLA2).ConclusionDiscordance between apoB and LDL-PNMR in routine clinical practice is more widespread than currently recognized and may be associated with insulin resistance.