Standardizing the Definition of AKI

By the bioMérieux Connection Editors

Acute Kidney Injury (AKI) is a potentially fatal condition that normally occurs as a comorbidity of other serious illnesses. Serious cases of AKI require dialysis, which helps to support kidney function while the kidneys recover. Clinical diagnosis of AKI can be difficult because there are a wide range of associated symptoms—and sometimes cases are asymptomatic.

For this reason, it is critical that healthcare providers have reliable methods of evaluating kidney function. Effective therapeutic intervention is essential for improving patient outcomes. The development of these interventions relies heavily on research studies that routinely collect health care data. The usefulness of this research, however, depends on a consistent definition of AKI.

Studying Inconsistencies in AKI Research

Consistency in AKI reporting was the topic of a recent article in which an international panel of 55 medical experts examined 174 studies that fit specific criteria. The goal of this panel was to achieve consensus on how the definition of AKI should be applied.

The definition of AKI has evolved since the term was first used in 1918. The current definition is based on the previous two classifications and had the aim of unifying the definition of AKI and was proposed by the KDIGO (Kidney Disease: Improving Global Outcomes) Acute Kidney Injury Working Group. Under the KDIGO definition, AKI is diagnosed by an absolute increase in serum creatinine, at least 0.3 mg/dL (26.5 μmol/L) within 48 hours, or by a 50% increase in serum creatinine from baseline within 7 days, or a urine volume of less than 0.5 mL/kg/h for at least 6 hours.

Of the 174 studies reviewed by the panel, 15.5% did not provide detail on how they measured AKI, except that they used the KDIGO definition; 28.2% gauged AKI via urine output; 77.4% used a 48-hour measure of 0.3 mg/dL creatinine increase; and 20.7% did not define baseline creatinine. Only 19.5% defined recovery of kidney function.

The Journey Toward Consensus

The panel concluded, “The current methods for defining AKI using routinely collected data are inconsistent and poorly described in the available literature. The KDIGO guidelines should be extended to include a standardized definition for how AKI should be defined when using routinely collected data.”

The panel came to a consensus on and recommends the following when defining AKI for research via the KDIGO definition:

  1. Report whenever creatinine rose 0.3 mg/dL in 48 hours and if stage I, II, or III criteria are used
  2. Define timeframe for development of AKI
  3. When defining baseline kidney function include timeframe and if inpatient and outpatient creatinine data were used; if baseline creatinine was excluded, state what was used in its place
  4. State which patient groups, if any, were excluded from analysis
  5. Extend KDIGO guidelines to include a standard process for how to define AKI when using routinely collected data

AKI is a serious condition associated with poor patient outcomes, and more can be done to help ensure patients are receiving proper treatment. Developing interventions to improve patient outcomes requires thorough research based on reliable data. As part of that, establishing universal definitions and practices in analyzing routinely collected data could aid researchers in the design of epidemiologic studies and randomized trials of preventive and therapeutic interventions.


Opinions expressed in this article are not necessarily those of bioMérieux, Inc.

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