This study was a diagnostic research, so the content was decomposed according to PIRO : P: Patients diagnosed with sudden death; I: C-reactive protein; R: There is no gold standard for sudden death, and the definition of sudden death varies from literature to literature. The World Health Organization defines sudden death: "Patients who are normally healthy or seemingly healthy die suddenly due to natural diseases in an unexpectedly short period of time." In our study, sudden death is determined by the history, symptoms, physical examination and electrocardiogram results assesed by doctor. If death events were collected from the patients’ medical records, deaths coded using the International Classification of Diseases-9th Revision, codes 410 to 414 for non-SCD and 798.1 for SCD; or the International Classification of Diseases-10th Revision, codes I20 to I25 for non-SCD and I46 for SCD. All deaths registered as sudden deaths were confirmed in interviews with the patient’s physician or family members again. O: sudden death.