Test Overview
Test Usage

Effective 01/05/2022, Michigan Medicine adopted an updated CKD-EPI equation for estimated glomerular filtration rate (eGFR) that does not include race as a variable. All eGFR
results will be expressed as a single “eGFR” and no longer distinguish between “eGFR, Black” and “eGFR, Non-Black”.

There is consensus that elimination of the race modifier used to calculate “eGFR, Black” is appropriate given that race is a social and not a biologic construct. The National Kidney Foundation (NKF) and American Society of Nephrology (ASN) Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease affirmed this position in a formal release on 9/23/2021 (Delgado C, et al. A Unifying Approach for GFR Estimation: Recommendations of the NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease. Am J Kidney Dis. 2021 Sep 23:S0272-6386 (21)00828-3. PMID: 34563581).

However, there are CAVEATS to be considered in the clinical application of the common eGFR 2021 CKD-EPI, creatinine. For additional background on this change, see Inker LA, et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. N Engl J Med. 2021 Nov 4;385 (19):1737-1749. PMID: 34554658.

In scenarios where a more accurate or confirmatory GFR may be required for clinical decision-making, consider additional options such as timed urine collection for creatinine clearance; cystatin C testing; or nephrology referral for formal GFR assessment or measurement.

As recommended by the NKF and ASN, this reported eGFR value was calculated using the 2021 CKD-EPI creatinine equation. Calculated eGFR may be inaccurate when kidney function is unstable. This equation has NOT been validated for children under the age of 18 years or for pregnant women. An eGFR between 15 and 59 mL/min/1.73m2 for greater than or equal to 3 months is classified as Chronic Kidney Disease Stage 3 or 4.

Reference Range *

2021 CKD-EPI ≥ 60 mL/min/1.73m^2

GFR Category: GFR (mL/min/1.73m^2): Interpretation:
G1 90 or greater Normal or high*
G2 60-89 Mild decrease*
G3a 45-59 Mild to moderate decrease
G3b 30-44 Moderate to severe decrease
G4 15-29 Severe decrease
G5 14 or less Kidney failure
*In the absence of evidence of kidney damage, neither GFR category G1 nor G2 fulfill the criteria for CKD (Kidney Int Suppl 2013;3:1-150)

Test Limitations

2021 CKD-EPI calculations are not valid for patients less than 18 years of age and for pregnant women.
The 2021 CKD-EPI formula used to calculate the EGFR result has not been validated in patients > 100
years of age.
EGFR is not calculated when serum creatinine values are <0.1mg/dL [11/20]
The EGFR should NOT be used for pharmacy drug dosing.
The calculation is not useful for estimating GFR in unstable patients or
patients with acute renal failure. There are other conditions where the EGFR will be less
accurate and should not be utilized. These include: extremes of body size and weight, skeletal
muscle disease, paraplegia or quadriplegia, vegetarian diet, and for the calculation of dose of
potentially toxic drugs that are excreted by the kidney. [11/20]

Test Details
Days Set Up
Daily, 24 hours
Analytic Time

2 hours

Soft Order Code
Non-orderable - GFR
MiChart Code
Non-orderable - Estimated GFR, Creatinine-based formula (CKD-EPI 2021)
Laboratory
Chemical Pathology
Section
Automation
STAT Availability

STAT requests for this test will be performed on a STAT basis (supervisory staff approval is not required).

Specimen Requirements
Collection Instructions

Collect specimen in an SST tube. Centrifuge within 4 hours of collection, aliquot serum into a plastic vial and refrigerate. If specimen cannot be centrifuged at client site, please arrange for delivery to MLabs within 3 hours of specimen collection.

Contraindications
GFR estimate can be interpreted accurately only during a steady state of creatinine balance. GFR estimate will overestimate true GFR if serum creatinine is rising (such as acute kidney failure) and will underestimate true GFR if serum creatinine is declining (such as resolution of acute kidney failure).
Normal Volume
1 mL
Minimum Volume
0.5 mL
Additional Information

The Jaffe reaction used for creatinine on the Atellica CH930 can exhibit a positive bias or interference with a number of different compounds. The most common are high levels of ascorbic acid and certain cephalosporin antibiotics (Cefpirone, Cefoxitin, Cefazolin, and Cephalothin). Patients may exhibit fairly dramatic changes in serum creatinine (0.5 - 1.0 mg/dL increases) if samples happen to be drawn at peak drug levels.

Billing
NY State Approved
No