Examining Low Rates of Real-World Lp(a) Testing: Insights From a Decade-Long Cohort Study in a Diverse Health System

The results of a recent retrospective cohort study found low rates of real-world lipoprotein(a) (Lp[a]) testing within a large, diverse health system between 2010 and 2021. Furthermore, certain patient characteristics were associated with disparities in testing rates.¹ The findings were presented as a poster, “Predictors of Lp(a) Testing Among Multiethnic Individuals” during a session at the American Heart Association Scientific Sessions 2023, which ran from November 11 to 13, 2023, in Philadelphia, Pennsylvania.¹

Lp(a) is an apolipoprotein B–containing lipoprotein with atherogenic potential.^2,3 A high concentration of Lp(a) in the blood is associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD).⁴

Investigators from Stanford Cardiovascular Institute, Stanford Medicine, and other institutions analyzed data from Sutter Health, a Northern California health system treating over 3 million patients, to determine the prevalence of Lp(a) testing, as well as to identify any specific patient characteristics that were associated with those patients who received testing. Patients who were 18 years or older and who had at least 2 primary care visits between 2010 and 2021 were included in the study. Those patients who had at least 1 Lp(a) laboratory test ordered were defined as Lp(a) cases. Incident density matching was used to select controls matched with Lp(a) cases by visit date at a ratio of 5:1. The investigators used conditional logistic regression to assess associations between Lp(a) testing and individual patient demographics, including age, gender, race and ethnicity, and certain clinical characteristics.¹

A total of 1,484,410 patients were included in the cohort. Of this total, only 1% of patients (n = 14,818) underwent Lp(a) testing during the study period. In the tested cohort, the mean age was 54.3 years and 48.1% of the population was female, while in the untested cohort, the mean age was 51.6 years and 59.3% of the population was female. Additionally, among those who underwent Lp(a) testing, there was a lower prevalence of Hispanic ethnicity, and a higher prevalence of patients who identified as non-Hispanic Asian, and specifically as South Asian. The prevalence of ASCVD was more than doubled in the tested cohort compared with the untested cohort (17.5% vs 8.6%). However, in patients without a diagnosis of ASCVD, the mean 10-year ASCVD risk was higher among those who were not tested (9.70%) than those who underwent testing for Lp(a) (6.30%), and a greater proportion of patients in the untested cohort had a 10-year ASCVD risk of greater than 20%. Preferred provider organization or fee-for-service was the primary insurance coverage for 55.6% of those tested and for 49.6% of those who were not tested, and the prevalence of Medicaid/Medi-Cal or Medicare coverage was lower among tested patients. Furthermore, a greater proportion of patients who underwent Lp(a) testing had cardiology visits and statin prescriptions.¹

Among those who were assessed, the median concentration of Lp(a) was 35 mg/dL. Investigators emphasized differences in testing rates associated with patient race and ethnicity: compared with non-Hispanic White patients, South Asian patients were 3 times more likely to have undergone Lp(a) testing (odds ratio [OR], 3.19; 95% Cl, 2.98-3.41) whereas non-Hispanic Black and Hispanic patients were less likely to have undergone testing (OR, 0.70; 95% Cl, 0.62-0.80; and OR, 0.64; 95% Cl, 0.59-0.69; respectively). Additionally, having history of ASCVD was noted to be associated with over twice the likelihood of undergoing testing (OR, 2.14; 95% CI, 1.99-2.29).¹

According to the 2019 clinical practice guidelines released by the American College of Cardiology and American Heart Association Task Force, an Lp(a) of at least 50 mg/dL is a risk-enhancing factor for CVD, and the National Lipid Association notes that Lp(a) levels above 30 mg/dL are associated with coronary heart disease and emphasizes that elevated Lp(a) is an independent, causal risk factor for both cardiovascular and all-cause mortality.^2,4

The American Association of Clinical Endocrinologists/American College of Endocrinology Guidelines for Management of Dyslipidemia and Prevention of Cardiovascular Disease note that Lp(a) testing should be considered in certain patients, including patients with clinical ASCVD, a family history of premature ASCVD or increased Lp(a), a 10-year ASCVD risk of at least 10%, and South Asian or African ancestry.⁵ Furthermore, elevated Lp(a) levels may inform appropriate pharmacotherapeutic treatment decision-making.^2,4

These study results provide real-world data on implementation of Lp(a) testing in Northern California, showing consistently low testing rates between 2010 and 2021, as well as differences in testing rates by patient race and ethnicity. Certain findings indicate that clinical practice aligns with guideline recommendations, including higher testing rates among South Asian patients and those with a history of ASCVD; yet, low rates of testing among Black patients and those at highest risk of ASCVD indicate inconsistencies in aligning to testing guidelines.¹ For example, Black patients have an approximately 3-fold higher median concentration of Lp(a) than do White patients, but results of the analysis showed that Black patients were 30% less likely to undergo Lp(a) testing than were White patients.^1,3,4 Study investigators asserted that expanding Lp(a) testing access may help reduce disparities in ASCVD risk assessment and treatment.¹

References

1. Brar S, Huang Q, Yan S, et al. Predictors of Lp(a) testing among multiethnic individuals. Poster presented at: American Heart Association Scientific Sessions 2023; November 11-13, 2023; Philadelphia, PA. GR.APS.P5.
2. Grundy SM, Stone NJ-bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2019;73(24):3168-3209. doi:10.1016/j.jacc.2018.11.002
3. Reyes-Soffer G, Ginsberg HN-berglund L, et al. Lipoprotein(a): a genetically determined-causal, and prevalent risk factor for atherosclerotic cardiovascular disease: a scientific statement from the American Heart Association. Arterioscler Thromb Vasc Biol. 2022;42(1):e48-e60. doi:10.1161/ATV.0000000000000147
4. Wilson DP, Jacobson TA, Jones PH, et al. Use of lipoprotein(a) in clinical practice: a biomarker whose time has come. A scientific statement from the National Lipid Association. J Clin Lipidol. 2019;13(3):374-392. doi:10.1016/j.jacl.2019.04.010
5. Handelsman Y, Jellinger PS, Guerin CK, et al. Consensus statement by the American Association of Clinical Endocrinologists and American College of Endocrinology on the management of dyslipidemia and prevention of cardiovascular disease algorithm – 2020 executive summary. Endocr Pract. 2020;26(10):1196-1224. doi:10.4158/CS-2020-0490