Tissue Kallikrein Activity, Detected by a Novel Method, May Be a Predictor of Recurrent Stroke: A Case-Control Study

Aim. Tissue kallikrein (TK) protein content in plasma has been shown to be negatively associated with both incident and recurrent strokes. The aims of this study were to develop a novel method for detecting TK activity and to investigate its association with event-free survival over 5 years in Chinese first-ever stroke patients. Methods. We designed a case-control study with 321 stroke patients (174: ischemic stroke, 147: hemorrhagic stroke) and 323 healthy local controls. TK activity was measured by a novel assay utilizing the immunological characteristics of TK and the catalysis of benzoyl arginine ethyl ester hydrochloride (BAEE). Results. TK protein levels above 0.200 mg/L in plasma were not associated with urinary TK activity or the risk of stroke recurrence. TK activity was significantly lower in stroke patients compared with controls (1.583 ± 0.673 Eu/mL versus 1.934 ± 0.284 Eu/mL, P < 0.001). After adjusting for traditional risk factors, TK activity was negatively associated, in a dose-response manner, with the risk of overall stroke recurrence and positively associated with event-free survival during a 5-year follow-up (relative risk (RR), 0.69; 95% CI, 0.57–0.84; P < 0.001). Conclusions. Our findings suggest that urinary TK activity may be a stronger predictor of stroke recurrence than plasma TK levels.