Q&A: KDIGO criteria

Q: The Kidney Disease Improving Global Outcomes (KDIGO) criteria defines acute kidney injury (AKI) as any of the following: “Increased creatinine level greater than or equal to 1.5 times the baseline (historical or measured), which is known or presumed to have occurred within the prior seven days.”

I understand that for patient with no history of chronic kidney disease (CKD), you can apply baseline creatinine level from six months or even one year previously. Can you please clarify when a creatinine level has to be within the prior seven days?

A: Let’s first start with KDIGO. As you have said, KDIGO defines AKI is as any of the following:

• An increase in serum creatinine by greater than or equal to 0.3 mg/dL within 48 hours; or
• An increase in serum creatinine by greater than or equal to 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or
• A urine volume less than 0.5 ml/kg/h for 6 hours.

The timing of when a serum creatinine was measured and how it is applied has some very strict rules in KDIGO. Per KDIGO:

It is reasonable for a patient without chronic kidney disease or an individual with previous normal renal function to assume that serum creatinine will be stable over several months/years. Serum creatinine levels obtained during this timeframe would reasonably reflect one’s pre-morbid baseline.

Although Coding Clinic states that old information with no bearing on the current stay should not be reported or resourced, the KDIGO guidelines clearly require consideration of previous serum creatinine levels for the current state of practice in evaluating AKI. We must understand the individual’s baseline to evaluate and compare present renal function.

We must establish a baseline value and trend the creatinine. The creatinine values are important, but the timing of the creatinine measurement in relation to the admission is also of critical importance. You need more than one creatinine measurement in order to see the trending data:

• Prospective measurement: When the creatinine rise is measured during the inpatient hospitalization within a 48-hour period.
• Retrospective measurement: Any measurement taken when the creatinine is already elevated and is in the process of decreasing.

Let’s review these timing definitions a bit further. The serum creatinine increase by greater than 0.3 mg/dL can only be used when measured prospectively, when the baseline has been measured during the preceding 48 hours, or if the patient’s baseline is known from previous records and renal function was considered stable prior to admission.

If the measurement occurs retrospectively, the diagnosis cannot be made until the downward trend stabilizes and will require the higher threshold of a difference of greater than 1.5 times the baseline value. A retrospective measurement is one in which the creatinine was already elevated upon arrival to the emergency department; the levels are only measured as they decrease during the stay. If we have no reliable baseline from previous visits, a baseline is not known with a retrospective measurement until the patient is rehydrated and stable.   

If the measurement occurs retrospectively, the diagnosis cannot be made until the downward trend stabilizes and will require the higher threshold of a difference of greater than or equal to 1.5 times the baseline value.

For example: A patient with a measured stabilization at 0.8 mg/dL after hydration would have required a measurement of 1.2 mg/dL before a diagnosis could be made retrospectively. That is an increase of 0.4 mg/dL. 

Obviously, these assessments require serial labs or basic metabolic panels in order to better evaluate the changing creatinine levels. You need more than one creatinine measurement in order to see the trending data.

KDIGO also states that the lowest measured serum creatinine taken during a hospitalization stay may be assumed to be the newest baseline measurement for the purposes of diagnosing acute kidney injury in an acute care setting. 

If the lowest measured serum creatinine during a stay is lower than a previous measured baseline, use the lowest serum creatinine measured as the baseline.

The serum creatinine does not need to be elevated for 24 hours or more before being considered as a valid data point. Renal recovery status post IV fluids occurs very rapidly in many pre-renal scenarios, and a rapid drop in serum creatinine status post IV hydration is an expected finding.

The prospective measurement can only be used when we have an understanding of the patient’s baseline function. You can use this formula if you have access to historical trending, or if the creatinine is noted to rise from the level reported on admission. Otherwise, we would need to trend the creatinine and determine function based on a retrospective view.

Editor’s Note: Laurie Prescott, RN, MSN, CCDS, CCDS-O, CDIP, CRC, CDI education director at HCPro, answered this question. For information regarding CDI Boot Camps, click here.