Usefulness of serum tryptase level as an independent biomarker for coronary plaque instability in a Chinese population.

Tryptase and chymase are unique mast cell proteases that are essential in atherogenesis. This study establishes a link between serum tryptase and chymase levels and human coronary heart diseases (CHD) in a cohort of 270 subjects. Serum tryptase levels were significantly higher in patients with substantial CHD than in those without substantial CHD (substantial CHD vs. unsubstantial CHD: 7.81 ± 0.52 ng/mL vs. 6.11 ± 0.51 ng/mL, P=0.002). After subgrouping the substantial CHD patients into those with acute myocardial infarction (AMI) and those with unstable or stable angina pectoris (UAP or SAP), we demonstrated that serum tryptase levels were nearly doubled in AMI patients as compared with unsubstantial CHD patients (11.13 ± 1.55 ng/mL vs. 6.11 ± 0.51 ng/mL, P<0.01), and significantly higher than in UAP patients (7.19 ± 0.62 ng/mL, P<0.05) or SAP patients (6.80 ± 0.94 ng/mL, P<0.05). Although Spearman's correlation test showed that serum tryptase correlated significantly with age (P=0.014) and weakly with fasting glucose (P=0.084), total cholesterol (P=0.071), low-density lipoprotein (P=0.063), and triglyceride (P=0.058), serum tryptase levels remained significantly higher in substantial CHD patients than in unsubstantial CHD patients in a multiple linear regression test after adjusting for all these confounders (P=0.008). Serum chymase levels were also higher in AMI patients (27.64 ± 7.57 ng/mL) or UAP patients (24.62 ± 8.06 ng/mL) than in SAP patients (15.20 ± 0.81 ng/mL) or unsubstantial CHD patients (16.84 ± 0.56 ng/mL), although such differences were not statistically significant. Spearman's correlation test revealed that serum chymase levels correlated significantly only with fasting glucose levels (P=0.019), and CHD status did not affect chymase levels before and after adjusting for all confounders. Our observations suggest that serum tryptase is an independent biomarker for coronary plaque stability in this Chinese population.