The PLAC^® Activity Test is an FDA-cleared enzyme assay for the in vitro quantitative determination of Lp-PLA₂ (lipoprotein-associated phospholipase A2) activity in ethylenediaminetetraacetic acid (EDTA) plasma and serum on automated clinical chemistry analyzers. The PLAC Activity Test is to be used in conjunction with clinical evaluation and patient risk assessment as an aid in predicting risk for coronary heart disease (CHD) in patients with no prior history of cardiovascular events.

The PLAC Activity Test is substrate based and is conveniently performed using a wide range of automated clinical chemistry analyzers.

Patients with normal cholesterol remain at risk for CHD

• In a large cohort of patients hospitalized with coronary artery disease, nearly 50% had admission LDL levels <100 mg/dL¹
• Patients with low and moderate CHD risk still have a significant risk for events for over 10 years²
• When assessing CHD risk, cholesterol testing alone is not always enough³

The PLAC Activity Test

• Novel risk prediction for CHD in patients with no prior history of cardiovascular events
• Prognostic value independent of standard lipid profile testing
• Valuable risk predictor for patients without hypercholesterolemia
• Validated in thousands of patients in multicenter substudy using a cut point of 225 nmol/min/mL
• At the cut point of 225 nmol/min/mL, the primary composite end point of risk for CHD events was reached (Figure 1)
• The cut point of 225 nmol/min/mL achieved statistical significance for each individual risk component (Table 1)

Flexibility and performance for the clinical laboratory Validated on multiple automated chemistry analyzers Robust analytical performance with high degree of accuracy and precision Validated cut point of 225 nmol/min/mL

The REGARDS* multicenter study and the PLAC Activity Test

• One of the largest National Institutes of Health (NIH) studies ever undertaken, with over 30,000 patients enrolled across the United States
• The Lp-PLA₂ substudy examined 4,598 case-matched patients
• A cut point of 225 nmol/min/mL was prospectively assigned based on prior studies and publications
• In a REGARDS multicenter substudy, high Lp-PLA2 activity was more closely associated with outcome than high low-density lipoprotein cholesterol (LDL) and low high-density lipoprotein cholesterol (HDL). Only status of diabetes or smoking was more closely associated with events (Figure 2)

* Reasons for Geographic and Racial Differences in Stroke.

The PLAC Activity Test is analytically robust, allowing for adoption of Lp-PLA₂ activity in clinical practice⁶

PERFORMANCE EVALUATION OF AN AUTOMATED ASSAY FOR Lp-PLA₂ ACTIVITY:

Clinical Chemistry; Vol. 59, No. 10. Supplement, 2013
Callahan H, Jaffe AS, Saenger AK; Mayo Clinic: Rochester, MN

We collaboratively developed and validated an automated Lp-PLA₂ activity assay. Specific test parameters for Lp-PLA2 activity were determined using an open, user-defined channel on the Roche Cobas® 600/c501 Chemical Analyzer.

Analytical performance was established and assessed across multiple parameters:

• Sample stability for Lp-PLA₂ activity was established using serum and ethylenediaminetetraacetic acid (EDTA) plasma; ≤4 hours ambient, ≤31 days refrigerated, and ≤31 days frozen at either -20°C or -70°C
• For serum Lp-PLA₂ activity, the Beckman Coulter AU400® Clinical Chemical Analyzer and the Cobas 600/c501 were highly correlated with minimal bias (y = 0.9911x + 0.926; r2 = 0.999)
• Four (4) lot-to-lot comparisons demonstrated excellent correlation (slope: 0.98 to 1.03; r2 ≥ 0.999)
• On-board reagent stability was validated for up to 61 days
• Assay linearity was established between 10 to 400 nmol/min/mL in this analysis
• Accuracy was proven with mean recoveries between 96% and 103%
• Within run precision, 0.4% to 0.7%
• Between-assay precision, 1.5% to 1.7%

Lp-PLA₂ assay performance summary

• Test using serum and EDTA plasma
• Highly correlated across platforms and lot to lot
• On-board and refrigerated reagent stability
• Excellent precision within run and between run
• Linearity established across the analytical range
• Highly accurate assay measurements

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