Sorted By Test Name - Mayo Medical Laboratories

CRC
8500
12-17 years: 94-499 U/L
> or =18 years: 52-336 U/L
Females
6-7 years: 134-391 U/L
8-14 years: 91-391 U/L
15-17 years: 53-269 U/L
> or =18 years: 38-176 U/L
Reference values have not been established for patients that are less than 6 years of age.
Note: Strenuous exercise or intramuscular injections may cause transient elevation of CK.
Clinical References: Tietz Textbook of Clinical Chemistry, Edited by CA Burtis, ER Ashwood, WB
Saunders Company, Philadelphia, 1999
Creatinine Clearance
Clinical Information: Glomerular filtration rate (GFR) is the sum of filtration rates in all functioning
nephrons and so an estimation of the GFR provides a measure of functioning nephrons of the kidney. A
decrease in GFR implies either progressive renal disease, or a reversible process causing decreased
nephron function (eg, severe dehydration). One of the most common methods used for estimating GFR is
creatinine clearance. Creatinine is derived from the metabolism of creatine from skeletal muscle and
dietary meat intake, and is released into the circulation at a relatively constant rate. Thus, the serum
creatinine concentration is usually stable. Creatinine is freely filtered by glomeruli and not reabsorbed or
metabolized by renal tubules. However, approximately 15% of excreted urine creatinine is derived from
proximal tubular secretion. Because of the tubular secretion of creatinine, the creatinine clearance
typically overestimates the true GFR by 10-15%. Creatinine clearance is usually determined from
measurement of creatinine in a 24 hour urine specimen and from serum specimen obtained during the
same collection period. The creatinine clearance is then calculated by the equation: 2.54 cm = 1 inch 1 kg
= 2.2 pounds (lbs) Patient Surface Area (S.A.) = wt (kg)(.425) X ht (cm)(.725) X 0.007184 Urine conc
(mg/dL) x 24 hr Urine volume (mL) Uncorr. creat. clear. = 1440 minutes_____ = ml/min Plasma Creat
(mg/dL) Urine conc (mg/dL) x 24 hr Urine volume (mL) Corr. creat. clear. = 1440 minutes_______ x
1.73m(2) = ml/min/1.73m(2) Plasma Creat (mg/dL) Patient S.A.
Useful For: Estimation of glomerular filtration rate (GFR)
Interpretation: Decreased creatinine clearance indicates decreased glomerular filtration rate.This can
be due to conditions such as progressive renal disease, or result from adverse effect on renal
hemodynamics that are often reversible, including drug effects or decreases in effective renal perfusion
(eg, volume depletion, heart failure). Increased creatinine clearance is often referred to as hyperfiltration
and is most commonly seen during pregnancy or in patients with diabetes mellitus, before diabetic
nephropathy has occurred. It may also occur with large dietary protein intake. A major limitation of
creatinine clearance is that its accuracy worsens in relation to the amount of tubular creatinine secretion.
Often as GFR declines, the contribution of urine creatinine from tubular secretion increases, further
increasing the discrepancy between true GFR and measured creatinine clearance.
Reference Values:
Creatinine Clearance: 70-135 mL/min/SA
Urine: reported in units of mg/dL
Serum
Males
12-24 months: 0.1-0.4 mg/dL
3-4 years: 0.1-0.5 mg/dL
5-9 years: 0.2-0.6 mg/dL
10-11 years: 0.3-0.7 mg/dL
12-13 years: 0.4-0.8 mg/dL
14-15 years: 0.5-0.9 mg/dL
> or = 16 years: 0.8-1.3 mg/dL
Reference values have not been established for patients that are less than 12 months of age.
Females
Current as of January 4, 2013 7:15 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 545