Influenza clinical risk groups 2017 version - Chronic renal disease diagnoses

Read v2 codes for a diagnosis of long-term kidney disease as an indication for influenza vaccination, including CKD stages 3-5, a history of renal transplant, dialysis or arteriovenous fistula, or nephrotic syndrome. Read v2 codes for CKD stages 1-2 and "resolved" CKD are also included, with an indicator flag. For this project, individuals were considered to have long-term kidney disease if: they had any code in this list AND the latest code before the index date was neither CKD resolved (resolved=1) nor CKD stage 1 or 2 (stage1_2 flag=1). Definition designed to follow national guidance in indications for influenza vaccination https://www.gov.uk/government/publications/influenza-the-green-book-chapter-19