Because chronic kidney disease (CKD)
is poorly inferred from serum creatinine alone, NKDEP strongly
encourages clinical laboratories to routinely estimate and report GFR
when serum creatinine is measured for patients 18 and older, when
appropriate and feasible. Routinely reporting eGFR with all serum
creatinine determinations allows laboratories to help identify reduced
kidney function for providers, thus facilitate the detection of CKD.
Routine reporting is easier for some laboratories than it is for
others. The following information will help laboratories appropriately
report eGFR.
Common
problems. Below are considerations for
addressing common issues laboratories face when reporting eGFR:
- Since a patient's race is often not
available to laboratories, and because mixed ethnicity can make it
difficult to classify a patient's race, a general recommendation is to
report the eGFR values for both African Americans and non-African
Americans. (See Sample
eGFR Reports.) This practice allows the provider to estimate
the appropriate value for the patient's ethnicity. When ethnicity is
known, it is acceptable to report a single eGFR appropriate for the
race.
- Comments can supplement the
calculated eGFR in cases where the laboratory’s information
system cannot be programmed to report estimates based on race (African
American or not African American). For example, if eGFR is reported
based on the non-African American equation, a comment could state
“For African Americans, multiply by 1.212.”
- The laboratory should exercise
discretion regarding reporting multiple eGFR values when data for age
or gender are not available.
- Laboratories
may want to restrict eGFR reporting for some
patients. In cases where information systems cannot identify
patients for whom reporting eGFR is inappropriate, it is suggested that
laboratories report eGFR for all patients and allow the provider to
determine the suitability of a result for a patient’s
condition.
Reporting Values
≥60mL/min/1.73m2. NKDEP recommends reporting eGFR
values greater than or equal to 60 mL/min/1.73 m2
simply as ≥60 mL/min/1.73 m2, and not
as an exact number. For values below 60 mL/min/1.73 m2,
the report should give the numerical estimate rounded to a whole number
(e.g., "32 mL/min/1.73 m2).
There are three reasons for this recommendation:
- Interlaboratory differences in
calibration of creatinine assays and the imprecision of the
measurements have their greatest impact in the near-normal range and,
therefore, lead to greater inaccuracies for values ≥ 60
mL/min/1.73 m2 .1,
2
- The MDRD Study equation has been most
extensively evaluated in people with CKD and reduced GFR, and is less
accurate for persons with normal or mildly impaired kidney
function. 2,
3,
4,
5,
6,
7,
8,
9,
10
- Quantification of eGFR values below
60 mL/min/1.73 m2 has more clinical
implications for classification of kidney function than values above
this level.
References
1.
Myers GL, Miller WG, Coresh J, Fleming J, Greenberg N, Greene T,
Hostetter T, Levey AS, Panteghini M, Welch M, Eckfeldt JH.
Recommendations for improving serum creatinine measurement: a report
from the laboratory working group of the National Kidney Disease
Education Program. Clinical Chemistry. 2006;52:5–18.
2.
Coresh J, Astor BC, McQuillan G, Kusek J, Greene T, Van Lente F, Levey
AS. Calibration and random variation of the serum creatinine assay as
critical elements of using equations to estimate glomerular filtration
rate. American Journal of Kidney Disease.
2002;39(5):920–929.
3.
Poggio ED, Wang X, Greene T, Van Lente F, Hall PM. Performance of the
modification of diet in renal disease and Cockcroft-Gault equations in
the estimation of GFR in health and in chronic kidney disease. Journal
of the American Society of Nephrology.
2005;16(2):459–466.
4.
Bostom AG, Kronenberg F, Ritz E. Predictive performance of renal
function equations for patients with chronic kidney disease and normal
serum creatinine levels. Journal of the American Society of
Nephrology. 2002;13(8):2140–2144.
5.
Vervoort G, Willems HL, Wetzels JF. Assessment of glomerular filtration
rate in healthy subjects and normoalbuminuric diabetic patients:
validity of a new (MDRD) prediction equation. Nephrology,
Dialysis, Transplantation. 2002;17(11):1909–1913.
6.
Stoves J, Lindley EJ, Barnfield MC, Burniston MT, Newstead CG. MDRD
equation estimates of glomerular filtration rate in potential living
kidney donors and renal transplant recipients with impaired graft
function. Nephrology, Dialysis, Transplantation. 2002;17(11):2036–2037.
7.
Lin J, Knight EL, Hogan ML, Singh AK. A comparison of prediction
equations for estimating glomerular filtration rate in adults without
kidney disease. Journal of the American Society of Nephrology.
2003;14(10):2573–2580.
8.
Rule AD, Gussak HM, Pond GR, Bergstralh EJ, Stegall MD, Cosio FG,
Larson TS. Measured and estimated GFR in healthy potential kidney
donors. American Journal of Kidney Disease.
2004;43(1):112–119.
9.
Hallan S, Asberg A, Lindberg M, Johnsen H. Validation of the
Modification of Diet in Renal Disease formula for estimating GFR with
special emphasis on calibration of the serum creatinine assay. American
Journal of Kidney Disease. 2004;44(1):84–93.
10.
Coresh J, Eknoyan G, Levey AS. Estimating the prevalence of low
glomerular filtration rate requires attention to the creatinine assay
calibration. Journal of the American Society of Nephrology.
2002;13(11):2811–2812.
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