The Value of Lipid Testing in Recognizing Residual Risk.

The accuracy of various lipid measurements, assays and calculations and their impact on clinical decision making is controversial. Equations for calculating LDL-C include Friedewald (FE), Martin Hopkins (MH), Sampson (S) as well as measuring direct LDL (d-LDL). Two Lp(a) assays, molar (nmol/L) and mass (mg/dL), exhibit inter-assay differences and variability in repeat measures due to lab or patient related factors. Non-HDL, apoB and hs-CRP are associated with residual risk, potentially optimizing risk stratification. This study aimed to assess the additional value of various assays and biomarkers at guiding treatment for residual risk. Baseline data from the Young Heart study of patients <60 years old with coronary artery disease (CAD) included total cholesterol, triglycerides, HDL, d-LDL, non-HDL, apoB, Lp(a) mass assay (mg/dL), Lp(a) molar assay (mmol/L) and LDL-C calculated using above equations. The median age of our 60 patients was 51, 70% male, with HTN (76.7%), HLD (91.7%) and obstructive CAD (88.3%). Triglycerides >150, >200 and >400 mg/dL were noted in 32%, 17% and 2% of patients, respectively. Only 42% of patients were at goal for LDL-C <70mg/dL (FE) and 48% for non-HDL <100 mg/dL (Table). When using the MH and S equations, and d-LDL, population at goal became 35%, 38% and 52% respectively. In patients at goal for LDL-C (<70 mg/dL), 9.7% had non-HDL >100 mg/dL and 6% had apoB >80 mg/dL. In those with non-HDL <100 mg/dL, apoB was also at goal at <80 mg/dL with no incremental value in recognizing residual risk. The two Lp(a) assays noted a median Lp(a) of 57.8 nmol/L and 46 mg/dL. Lp(a) above 75 or 125 nmol/L was recorded in 42% and 25% of patients respectively. With a mass assay, Lp(a) was above 30 or 50 mg/dL in 30% and 28% of patients respectively. A total of 13 patients (22%) with LDL <70 had hsCRP >2. Non-HDL and apoB similarly recognized a subgroup of patients not meeting goals despite achieving LDL-C targets. Hs-CRP recognized a substantial number of patients who may have an additional, independent component of risk. Newer LDL-C calculators identified more patients for intensified LDL-C lowering therapy. Despite assay differences regarding abnormal Lp(a) levels, high-risk identification was similar. Attention to laboratory accuracy and biomarkers of residual risk is crucial for optimizing treatment to improve cardiovascular outcomes. [ABSTRACT FROM AUTHOR]