By evaluating routine clinical practice data from the UK primary care database, researchers in this study want to gather information on the kidney function of patients with non-valvular atrial fibrillation (NVAF, irregularly heart beats which is not caused by a heart valve problem) who are treated with Rivaroxaban (non-vitamin K antagonist, brand name Xarelto) or vitamin K antagonists (VKAs). The study planned to enroll about 25,000 male or female patients who were at least 18 years old and were new users of Rivaroxaban or VKAs between 01 January 2014 and 30 September 2019. Researchers are especially interested in whether patients experienced under treatment any worsening in kidney function, the onset of acute kidney diseases or injuries. In addition, risk of worsening in kidney function in patients with or without diabetes or heart failures are of interest to the researchers.

Inclusion Criteria:

• aged ≥18 years in the IMRD-UK database
• a first prescription for either rivaroxaban or a VKA between 01 January 2014 and 31 March 2019. The date of the first rivaroxaban/VKA prescription will be set as the start date (start of follow-up for that patient). The follow-up will be extended until 30 September 2019 to ensure that each patient has at least 6 months of potential follow-up.
• a diagnosis of AF recorded any time before start date or within 2 weeks after start date.
• registered with their general practice at least 1 year before the start date and have a recorded prescription of any drug at least 1 year before the start date.
• registered with a general practice with data considered to be up-to-standard quality.

Exclusion Criteria:

• a prescription for any OAC before the start date - all first-time rivaroxaban/VKA users will therefore be OAC naïve
• a record of heart valve replacement or mitral stenosis any time before the start date or in the 2 weeks after the start date.
• a record of deep vein thrombosis, pulmonary embolism, or hip/knee surgery in the 3 months before the start date (because these are all alternative reasons for NOAC initiation).
• a record of ESRD (including renal transplant patients) on/before the start date

Patients aged ≥18 years with NVAF and no record of ESRD, with a first prescription for rivaroxaban or a VKA and no previous OAC use between 01 January 2014 and 30 September 2019

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