Sorted By Test Name - Mayo Medical Laboratories

CREAZ
8472
13-36 months: 0.1-0.4 mg/dL
4-5 years: 0.2-0.5 mg/dL
6-8 years: 0.3-0.6 mg/dL
9-15 years: 0.4-0.7 mg/dL
> or =16 years: 0.6-1.1 mg/dL
Reference values have not been established for patients that are less than 12 months of age.
Clinical References: 1. Post TW and Rose BD: Assessment of renal function: Plasma creatinine;
BUN; and GFR. In UpTo Date 9..1 Edited by BD Rose. 2001. 2. Kasiske BL, Keane WF: Laboratory
assessment of renal disease: clearance, urinalysis, and renal biopsy. In The Kidney. 6th edition. Edited by
BM Brenner. Philadelphia, W.B. Saunders, 2000, pp 1129-1170
Creatinine with Estimated GFR (MDRD), Serum
Clinical Information: Creatinine In muscle metabolism, creatinine is synthesized endogenously from
creatine and creatine phosphate. Creatinine is removed from plasma by glomerular filtration into the urine
without being reabsorbed by the tubules to any significant extent. Renal tubular secretion also contributes
a small quantity of creatinine to the urine. As a result, creatinine clearance often overestimates the true
glomerular filtration rate (GFR) by 10% to >20%. Determinations of creatinine and renal clearance of
creatinine are of value in the assessment of kidney function. Serum or blood creatinine levels in renal
disease generally do not increase until renal function is substantially impaired. Estimated GFR (eGFR)
Use of an estimating or prediction equation to estimate GFR from serum creatinine should be employed
for people with chronic kidney disease (CKD) and those with risk factors for CKD (diabetes,
hypertension, cardiovascular disease, and family history of kidney disease). Studies have shown that GFR
can be reliably estimated from serum creatinine in adults by utilizing the Modification of Diet in Renal
Disease (MDRD) Study equation, which includes the patient's age, sex, and race.(1,2) In Caucasian and
African American populations between the ages of 18 and 70 with impaired kidney function (eGFR 60 mL/min/1.73 m[2]). Some
advantages of the estimated GFR calculation are listed in the following paragraphs: -GFR and creatinine
clearance are poorly inferred from serum creatinine alone. GFR and creatinine clearance are inversely and
nonlinearly related to serum creatinine. The effects of age, sex, and, to a lesser extent, race, on creatinine
production further cloud interpretation. -Creatinine is commonly measured in routine clinical practice.
Microalbuminuria may be a more sensitive marker of early renal disease, especially among patients with
diabetic nephropathy. However, there is poor adherence to guidelines that suggest annual urinary albumin
testing of patients with known diabetes. Therefore, if a depressed eGFR is calculated from a serum
creatinine measurement, it may help providers recognize early CKD and pursue appropriate follow-up
testing and therapeutic intervention. -Monitoring of kidney function (by GFR or creatinine clearance) is
essential once albuminuria is discovered. Estimated GFR is a more practical means to closely follow
changes in GFR over time, when compared to direct measurement using methods such as iothalamate
clearance. -The MDRD equation is the most thoroughly validated of the estimating equations. It has been
extensively validated in patients with CKD and is currently being evaluated for other populations such as
people with normal GFR, people with diabetes, and Hispanics. New equations, or modifications of the
MDRD equation, may be necessary in these groups. -The MDRD equation is superior to other methods of
estimating GFR. The MDRD equation correlates better with measured GFR than other equations,
including the Cockcroft-Gault equation. The MDRD equation is also superior to a 24-hour creatinine
clearance measurement. Measured iothalamate clearance remains the gold standard for measuring GFR.
-Nephrology specialists already routinely use estimating equations. It has long been appreciated among
nephrologists that serum creatinine alone is an insensitive index of GFR. Therefore, renal specialists have
employed estimating equations to convert serum creatinine to an approximate GFR. Reporting eGFR
values with serum creatinine results allows primary care providers and specialists in other fields to better
interpret their results. -The MDRD equation does not require weight or height variables. From a serum
creatinine measurement, it generates a GFR result normalized to a standard body surface area (1.73 m[2])
using sex, age, and race. Unlike the Cockcroft-Gault equation, height and weight, which are often not
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