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Introduction

There is an increased incidence of coronary artery disease (CAD) in South Asian populations, regardless of whether they live in their native countries or overseas . Moreover, CAD tends to emerge earlier in their life . There is also increasing trend of cardiovascular disease among young people in Pakistan . Various mechanisms are involved in the pathogenesis of CAD. Oxidative stress occurs due to a local imbalance between the reactive oxygen species (ROS) and antioxidant defense which is thought to be an important contributor of atherogenesis . Oxidative stress mediates many pathways linked to atherosclerosis by forming oxidized low-density lipoprotein (LDL) cholesterol and foam cells. Reactive oxygen species particularly superoxide is thought to react rapidly with nitric oxide (NO), which results in the formation of highly reactive oxidant peroxynitrite, decreasing the availability of NO and thus impairing vasorelaxation . Thus, oxidative stress is a key event in pathogenesis of atherosclerosis leading to CAD and may be accelerated by various cardiovascular risk factors .

Gamma glutamyl transferase (GGT) is an enzyme responsible for the extracellular catabolism of glutathione. Recently, emerging evidence has shown that increased serum GGT is strongly associated with development of cardiovascular disease . Gamma glutamyl transferase activity has been detected in atheromatous plaques of carotid and coronary arteries where it colocalizes with oxidized LDL . Increase in GGT activity has been found to be associated with several cardiovascular risk factors especially hypertension and type 2 diabetes . Population-based studies have revealed a strong association between high levels of serum GGT and increased risk of atherosclerotic cardiovascular disease .

Serum GGT within its high reference range is an early and sensitive enzyme related to oxidative stress . There are other biological markers that are used to assess oxidative stress which include F ₂ isoprostanes, 8-hydroxydeoxyguanosine and protein carbonyls. These biomarkers are associated with oxidative damage to lipid, DNA and protein, but individually do not give a clear oxidative stress burden in the body. Furthermore, these tests are expensive and difficult to perform in our medical laboratory. A simple and inexpensive test as a surrogate marker of overall oxidative stress would be very useful for researchers investigating its relation with CAD in developing countries like Pakistan where alcohol is not consumed by majority of the population.

Atherosclerotic plaques, the hallmark of atherosclerosis, progressively narrow the coronary artery lumen and impair myocardial blood flow. Coronary angiography remains the gold standard for the diagnosis of CAD. However, this is an invasive and costly procedure for most of these poor patients with very limited source of income. A noninvasive cheap test for assessment of high-risk cardiac patients is desirable in our clinical setup. Based on the role of GGT for the assessment of oxidative stress and epidemiological studies, we postulate that GGT present in the serum, even within its upper reference range, is a promising biomarker for assessment of premature coronary heart diseases. The study aimed to estimate the diagnostic accuracy of the serum GGT and its relationship with the diagnosis of CAD in young Pakistani patients attending coronary angiography.