Discordance between apoB and LDL-c levels among general population

A cross-sectional survey study of US adults not taking statins showed discordantly high apoB levels relative to LDL-c or non–HDL-c levels, even among metabolically healthy participants.

This summary is based on the publication of Sayed A, Peterson ED, Virani SS, et al. - Individual Variation in the Distribution of Apolipoprotein B Levels Across the Spectrum of LDL-C or Non-HDL-C Levels. JAMA Cardiol. 2024 Aug 1;9(8):741-747. doi: 10.1001/jamacardio.2024.1310.

Introduction and methods

Background

Although LDL-c, non–HDL-c, and apoB levels are highly correlated, they can diverge because the cholesterol content of apoB particles is variable. As a marker of ASCVD risk, apoB has been recognized as being superior to LDL-c [1-5], and for patients with hypertriglyceridemia—who have more apoB particles than estimated by their LDL-c level—the current US guideline on the management of blood cholesterol gives a relative recommendation for measuring apoB [6].

However, it is unknown whether individuals with no metabolic risk factors exhibit a similar discordance between apoB and LDL-c levels. In addition, there are few data to translate the LDL-c goals and thresholds to their apoB equivalents.

Aim of the study

The authors (1) assessed the variability in the apoB level across the spectrum of LDL-c or non–HDL-c levels, (2) quantified discordance between apoB and LDL-c or non–HDL-c levels, and (3) evaluated whether discordance between levels of apoB and LDL-c or non–HDL-c is limited to people with metabolic risk factors.

Methods

In a cross-sectional study, data on apoB, total cholesterol, HDL-c, and triglyceride levels were collected from 12,688 participants aged ≥18 years in the National Health and Nutrition Examination Survey in the US between 2005 and 2016. To estimate LDL-c levels, the Martin-Hopkins equation was used. Exclusion criteria were statin use and triglycerides >400 mg/dL.

Discordance between apoB and LDL-c levels was the difference between the observed (measured) apoB level and the estimated apoB level (i.e., median apoB level for an individual’s LDL-c level). A metabolically healthy profile was defined as BMI 18.5–24.9 kg/m², triglycerides <150 mg/dL, and absence of diabetes.

Main results

Distribution of apoB level across spectrum of LDL-c or non–HDL-c levels

• For LDL-c values of 55, 70, 100, and 190 mg/dL, the corresponding population median apoB levels were 49, 60, 80, and 140 mg/dL, respectively.
• For any given LDL-c value, a range of apoB levels was observed.
• At an LDL-c level of 100 mg/dL, 50% of the population had an apoB level between 75 and 86 mg/dL (i.e., the 25th and 75th apoB percentiles, respectively, for that LDL-c level) and 95% of the population had an apoB level in the range of 66 to 99 mg/dL (i.e., the 2.5th and 97.5th apoB percentiles, respectively, for that LDL-c level).
• Across the spectrum of non–HDL-c values, substantial variability in the apoB level was also observed. • At a non–HDL-c level of 130 mg/dL, 95% of the population had an apoB level between 73 and 102 mg/dL.
• ApoB variability was highest for LDL-c values estimated using the Friedewald equation, lower when the Martin-Hopkins or Sampson equation was used, and lowest when using non–HDL-c values.

Discordance between apoB and LDL-c or non–HDL-c levels by subgroup

• The following characteristics were associated with greater positive discordance (i.e., higher observed versus estimated apoB level): older age, male sex, Hispanic ethnicity, obesity (BMI ≥30 kg/m²), diabetes, higher triglyceride levels, higher HbA1c levels, higher BMI, statin use, and poor metabolic health.
• Across all comparisons, variability within subgroups was greater than the between-group difference.
• Although individuals with metabolic risk factors were more likely to have discordantly high apoB levels, significant variability in the apoB level was also observed among metabolically healthy participants.

Conclusion

This cross-sectional study of a nationally representative sample of US adults not taking statins showed substantial variability in the apoB level across the spectrum of LDL-c or non–HDL-c levels and considerable discordance between apoB and LDL-c or non–HDL-c levels. In individuals with metabolic risk factors, measured apoB levels were, on average, higher than estimated based on LDL-c or non–HDL-c levels. However, discordantly high apoB levels were also observed among metabolically healthy participants. According to the authors, “[t]he current guideline approach for apoB testing only for those with hypertriglyceridemia appears [to be] too narrow.”

Find this article online at JAMA Cardiol.

References

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