The PLAC test is used to determine Lp-PLA2 in serum or plasma.

Lp-PLA2 stands for Lipoprotein-Associated Phospholipase A2.

The test is used to determine your cardiovascular risk disease, myocardial infarction and ischemic stroke associated with atherosclerosis. In recent years, a number of studies have been published pointing to Lp-PLA2 as a marker for determining cardiovascular risk.

Lp-PLA2 activity is to be used in conjunction with clinical evaluation and a risk assessment as an aid in predicting risk of coronary heart disease (CHD) in people with no prior history of cardiovascular events.

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Lp-PLA2 is a calcium-independent phospholipase A2 enzyme that is associated with both low-density lipoprotein (LDL) and, to a lesser extent, high-density lipoprotein (HDL) in human plasma and serum and is distinct from other such phospholipases such as cPLA2 and sPLA2.2,3 Lp-PLA2 is produced by macrophages and other inflammatory cells and is expressed in greater concentrations in advanced atherosclerotic lesions than early-stage lesions.

Several lines of evidence suggest that oxidation of LDL plays a critical step in the development and progression of atherosclerosis.

Lp-PLA2 participates in the breakdown of oxidized LDL in the vascular wall by hydrolyzing the oxidized phospholipid, producing lysophosphatidylcholine and oxidized free fatty acids, both of which are potent pro-inflammatory products that contribute to the formation of atherosclerotic plaques.

Lp-PLA2 has demonstrated modest intra- and inter-individual variation, commensurate with other cardiovascular lipid markers and substantially less variability than high sensitivity C-reactive protein (hs-CRP). In addition, Lp-PLA2 is not elevated in systemic inflammatory conditions, and may be a more specific marker of vascular inflammation. The relatively small biological variation of Lp-PLA2 and its vascular specificity are of value in the detection and monitoring of cardiovascular risk.

References:

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- Kudo I, Murakami M. Phospholipase A2 enzymes. Prostaglandins Other Lipid Mediat. 2002 Aug;68-69:3-58. PubMed 12432908

- Burke JE, Dennis EA. Phospholipase A2 structure/function, mechanism, and signaling. J Lipid Res. 2009 Apr;50:s237-242. PubMed 19011112

- Hakkinen T, Luoma JS, Hiltunen MO, et al. Lipoprotein-associated phospholipase A(2), platelet-activating factor acetylhydrolase, is expressed by macrophages in human and rabbit atherosclerotic lesions. Arterioscler Thromb Vasc Biol. 1999 Dec;19(12):2909-2917. PubMed 10591668

- Kolodgie FD, Burke AP, Skorija KS, et al. Lipoprotein-associated phospholipase A2 protein expression in the natural progression of human coronary atherosclerosis. Arterioscler Thromb Vasc Biol. 2006 Nov;26(11):2523-2529. PubMed 16960105

- Witztum JL. The oxidation hypothesis of atherosclerosis. Lancet. 1994 Sep;344(8925):793-795. PubMed 7916078

- Chisolm GM, Steinberg D. The oxidative modification hypothesis of atherogenesis: an overview. Free Radic Biol Med. 2000 Jun 15;28(12):1815-1826. PubMed 10946223

- Macphee CH, Moores KE, Boyd HF, et al. Lipoprotein-associated phospholipase A2, platelet-activating factor acetylhydrolase, generates two bioactive products during the oxidation of low-density lipoprotein: use of a novel inhibitor. Biochem J. 1999 Mar 1;338(Pt 2):479-487. PubMed 10024526

- Macphee CH. Lipoprotein-associated phospholipase A2: a potential new risk factor for coronary artery disease and a therapeutic target. Curr Opin Pharmacol. 2001 Apr;1(2):121-125. PubMed 11714085

- Suckling KE, Macphee CH. Lipoprotein-associated phospholipase A2: a target directed at the atherosclerotic plaque. Expert Opin Ther Targets. 2002 Jun;6(3):309-314. PubMed 12223071

- Wolfert RL, Kim NW, Selby RG, Sarno MJ, Warnick GR, Sudhir K. Biological variability and specificity of lipoprotein-associated phospholipase A2 (Lp-PLA), a novel marker of cardiovascular risk (abstract). Circulation. 2004;110(Supplement 3):309.

- Lerman A, McConnell JP. Lipoprotein-associated phospholipase A2: a risk marker or a risk factor? Am J Cardiol. 2008 Jun 16;101(12A):11F-22F. PubMed 18549867

- Thompson A, Gao P, Orfei L, et al. Lipoprotein-associated phospholipase A(2) and risk of coronary disease, stroke, and mortality: collaborative analysis of 32 prospective studies. Lancet. 2010 May 1;375(9725):1536-1544. PubMed 20435228