A vascular inflammation marker for rupture-prone plaque
Your Laboratory can offer now a comprehensive cardiovascular risk assessment panel including i-plaq Test for Lp-PLA2 and help to identify modifiable risk factors for cardiovascular disease events.
What is the i-plaq Test?
The i-plaq Test for Lp-PLA2 is a simple blood test that measures the enzymatic activity of Lp-PLA2 (lipoprotein-associated phospholipase A2), a vascular specific inflammatory marker critical in the formation of rupture-prone plaque.
What is the test principle of the i-plaq Test?
The i-plaq test for Lp-PLA2 is an enzymatic activity assay and Lp-PLA2 in serum hydrolyzes the sn-2 position of the substrate, 1-myristoyl-2-(4- nitrphenylsuccinyl) phosphatidylcholine, producing a colored reaction product, 4-nitrophenol. The rate of formation of 4-nitrophenol is measured spectrophotometrically and the Lp-PLA2 activity is calculated from the rate of change in absorbance.
Which analyzers can run the i-plaq Test?
The most common clinical chemistry analyzers can be used for measuring the i-plaq Test for Lp-PLA2 like:
- Hitachi 917, Hitachi Roche P Modular,
- Roche Cobas 6000 / 8000 c501 & c502 / Cobas 8000 c701 & c711
- Beckman AU 480, 680, 5800
- Abbott Architect 4000 / c8000/ ci8200
- Siemens ADVIA 2400
- ERBA XL 180
Applications for other analyzers are in development.
What is the Calibration Procedure?
The i-plaq Test is calibrated with one human serum based calibrator and uses the internal blank or water blank as the zero point. The calibration curve is valid for 2 weeks with acceptable control performance. Two levels of human serum based controls, one high and one low, are available.
Specimen Collection and Storage
Serum is the recommended sample type:
- Fasting is not required
- Collect blood by venipuncture in serum collection tubes with our without gel separation
- Whole blood can be kept up to 4 hours at room temperature or up to 30 hours at 2-8 °C prior to
- Serum can be stored at:
- 8 hours at RT
- 1 week at 2-8 °C
- 1 year at -20 °C
- >2 years at – 70 °C
- Serum samples can be frozen and thawed up to 5 times.
Expected values for the i-plaq Test:
Proposed guidance values for the i-plaq test.
Each laboratory should establish its own reference ranges.
- The i-plaq test does not replace blood lipid testing or other traditional risk factors for CVD
Clinical Interpretation of the Lp-PLA2 values
People with high levels of Lp-PLA2 have an increased risk for CVD events independent from other CVD risk factors.
- Lp-PLA2 is produced in the plaque itself. It is vascular specific, unlike other inflammatory markers that measure systemic inflammation such as hs-CRP.
- The i-plaq Test may be used as a management tool in patients with intermediate to high risk for coronary heart disease or ischemic stroke events. The test results can help to set treatment goals and determine how aggressively the physician should treat risk factors.
- Tracking the reduction in Lp-PLA2 and LDL-C together in response to therapy is a better indicator of future CVD events than the reduction of LDL-C alone.
- Knowing that there is active disease, rather than just risk, may create a greater sense of urgency in patients to become more complaint with treatment recommendations.
(Source: The Lp-PLA2 Study Collaboration. Lipoprotein-associated phospholipase A2 and risk for coronary disease, stroke and mortality: collaborative analyses of 32 prospective studies. Lancet. 2010;375:1536-1544)
White HD, et al. J Am Heart Assoc. 2013;2:e000360)