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Table 1 Glossary of terms

From: Establishing a continuum of acute kidney injury – tracing AKI using data source linkage and long-term follow-up: Workgroup Statements from the 15th ADQI Consensus Conference

Variable Definition Comments
Electronic Health Record (EHR) The Electronic Health Record is a longitudinal electronic record of patient health information generated by one or more encounters in any care delivery setting. Included in this information are patient demographics, progress notes, problems, medications, vital signs, past medical history, immunizations, laboratory data and radiology reports. The EHR has the ability to generate a complete record of a clinical patient encounter, as well as supporting other care-related activities directly or indirectly via interface, including evidence-based decision support, quality management and outcomes reporting [31]. EHR serve as one source of data from which pertinent health information can be obtained. However, EHR are not ubiquitous and may result in incomplete data particularly as patients transition from one location to another.
Acute Kidney Injury (AKI) Evidence of an acute decline in kidney function characterized by an elevation in serum creatinine or reduction in urine output over a short interval of 48 h to 7 days [36]. Requires documentation of a measurable change in renal function in relation to a reference point. The time of diagnosis, maximum stage reached, clinical features (oliguric or not) and should be recorded. If ancillary criteria are used e.g. decline in creatinine these should be identified.
AKI Episode A discrete time period recognized with a starting point when diagnostic criteria are present and ending when there is evidence of improvement in renal function to meet criteria of recovery. Repeat episodes should be identified by evidence of a new decline in renal function following an improvement in renal function It is often difficult to determine exact start and end points of an AKI episode when creatinine and urine output are fluctuating. Criteria for classifying discrete episodes of AKI need to be developed.
AKI Follow-up Assessment of clinical and lab data at specific intervals following an AKI episode. Follow up should determine the level of general heath, level of renal function, consequences of the AKI on target organs and functional status and assess modifiable factors influencing outcomes. Specific interventions to improve recovery should be considered at each follow up visit. Data recording should distinguish single from multiple episodes that may be contiguous or separated in time. Analysis of the trajectory of serum creatinine changes could be used to track individual episodes. An electronic “tag” should be placed in patients record identifying the index episode to enable them being recognized as high risk for subsequent events.
Minimal Data set Set of variables that specifies the common data elements (CDE) that would be extracted at different time points after an episode of AKI (and then could be supplemented by additional data items). Core data elements should include: when the AKI episode occurred, location, etiology, associated events, key features in management, course, consequences and outcomes). The frequency of recording would be defined by best practices to allow timely interventions at patient centric levels. This minimum dataset would be the basis for both patient centric and population level tracking across geographic areas or jurisdictions.
Unique patient identifiers (UPI) A system that assigns individuals a unique number (the healthcare version of a Social Security Number) as a tool for patient identification across the different health care systems. Not available in all countries and settings.
Blue Button Initiative A system allowing patients and consumers access to their health records electronically through the “Blue Button” mechanism which allows consumers to take download and use their own health information. Blue Button originated at the Veteran’s Administration as a symbol on its patient portal that beneficiaries could click to securely download their own health record electronically. Since then the Blue Button has spread beyond VA to other to more than 450 government and the private sector organizations making personal health data available to Americans.
SNOMED The Systematized Nomenclature of Medicine is a systematic, collection of medical terms amenable for computer processing. It provides codes, terms, synonyms and definitions which cover anatomy, diseases, findings, procedures, microorganisms, substances, etc.  
Interoperability The ability of a system to exchange electronic health information with and use electronic health information from other systems without special effort on the part of the user. Interoperability is made possible by the implementation of standards.
Renal functional recovery from AKI Evidence of improvement in renal function to a level close to the reference point. There are variable definitions of complete and partial recovery in different studies [59, 60] Determining recovery is often difficult as there may be inadequate follow up of clinical and lab data as patients may be seen in different locations under different providers and systems. This is much easier when patients are cared for in a single health care system with shared data (e.g Veterans Affairs medical centres in the US or UK NHS)
Mortality Documentation of death, cause, contributing factors and time to death from onset of AKI. This endpoint should be measured at several time points from AKI diagnosis but at a minimum at hospital discharge and at 90 days post AKI.
Chronic kidney Disease (CKD) Status State of kidney health prior to development of AKI based on historical data. Consistency in determining and recording CKD stage is necessary. We recommend using consensus staging criteria and validated equation to calculate estimated glomerular filtration rate.