Risk stratification for Ischemic Stroke in Patients with Atrial Fibrillation Revisited: An investigation using the national TuRkish Atrial fibriallation (TRAF) registry Banu Evranos, Private Akay Hospital, Ankara, Turkey; Emre Oto, MITS, Ankara, Turkey; Naim Ata, Social Security Inst, Ankara, Turkey; Bünyamin Yavuz, Keçiören Training and Res Hosp, Ankara, Turkey; Deniz Katırcıoğlu Öztürk, MITS, Ankara, Turkey; Kudret Aytemir, Hacettepe University of Medical School, Ankara, Turkey; Altay Güvenir,Bılkent University Computer Engineering Department, Ankara, Turkey; Ergun Karaağaoğlu,Hacettepe Univ of Medical School, Ankara, Turkey; Emre Ertugay, Rasim Koselerli, Abdülkadir Bürkan, Mustafa Kuruca, Yadigar Gokalp Ilhan, Social Security Inst, Ankara, Turkey; John Camm, St. George's University of London, London, United Kingdom; Ali Oto, Hacettepe Univ of Medical School, Ankara, Turkey Objective: Stroke risk is not homogenous in atrial fibrillation(AF) and is identified by risk stratification schemes created by adding the risk factors. The impact of some risk factors for stroke has been debated. Our objective was to investigate risk factors for stroke in AF, and compare the traditional CHADS2 scheme with the new CHA2DS2-VASc risk scheme. Methods: We analyzed the records of patients over the age 18 who had the diagnosis of non-valvular atrial fibrillation (AF) according to ICD-10 code I48 from a claims and utilization management system called MEDULA which processes claims for all health insurance funds in Turkey since 2008. In this study we have used completely anonymized data. The risk of stroke was quantified for each patient on the basis of age, gender, and clinical risk factors for stroke using Cox proportional hazards regression models and estimates give as Hazard Ratios (HR) with 95% confidence intervals (CI). In order to quantify the predictive validity of these 2 stroke risk classification schemes, we calculated the c-statistics. Results: 402674 patients were diagnosed as nonvalvular AF during the 5 years study. Patients who did not receive warfarin (n=268,225) were identified and considered the sampling frame. The mean duration of follow-up was 24 months. There was an age-related increase in the risk of ischaemic stroke, for ages ≥75 years [HR (95% CI) 4,59 (4,32-4,87)] and ages between 65–74 years [HR 3,37 (3,16–3,58)]. Significant independent associations were found with prior ischaemic stroke [HR 2,49 (2.37– 2,64)], emboli [HR 1.38(1.18–1.62)], hypertension [HR 1.44(1.36–1.51)], diabetes mellitus [HR 1.16 (1.11–1,21)], female gender [HR 1.21 (1.14–1.28)], heart failure [HR 1.36 (1.32–1.42)] and hyperthyroidism[HR 1.10 (1.02–1.17)]. There was a significant increase in stroke risk over the age of 65 for women. A history of peripheral vascular disease, coronary artery disease, CKD and COPD were not independent risk factors for stroke. When we compared revised CHADS2 and categorised CHA2DS2VASc scores, the resulting c-indexes were 0.59 (95% CI, 0.58 to 0.59) and 0.54 (95% CI, 0.53 to 0.54), respectively. Conclusions: CHADS2 risk scheme better predicts ischeamic stroke and thromboembolic endpoint than CHA2DS2VASC risk scheme in AF patients. CHADS2 risk scheme underestimates the risk whereas CHA2DS2VASc risk scheme overestimates the risk. Both risk scheme has modest ability to predict ischeamic stroke and thromboembolic endpoint. A new risk scheme which augments the CHADS2 score system that emphasizes the role of age and encompasses gender appears to be inevitable.