Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (871 page)

   >16 years, male: 0.60–1.30 mg/dL

   
eGFR

   >16 years: >60 mL/minute/1.73 m
²

   Three equations are currently used for the calculation of GFR:

•   
IDMS-Traceable MDRD Study Equation for the calculation of GFR
:

ο   GFR (mL/minute/1.73 m
²
) = 175 × (S
_cr
)
^−1.154
× (age)
^−0.203
× (0.742 if female) × (1.212 if African American) (conventional units); where
S
_cr
is serum creatinine.

ο   (The equation has not been validated in children and will only be reported for patients >16 years of age. The equation is normalized for an average adult body surface area of 1.73 m
²
; weight and height adjustment is not necessary.)

•   Cockcroft-Gault formula

ο   CrCl = {((140 − age) × weight)/(72 SCr)} × 0.85 if female

ο   Where CrCl is expressed in milliliters per minute, age in years, weight in kilograms, and serum creatinine (SCr) in milligrams per deciliter.

•   The chronic kidney disease epidemiology collaboration (CKDEPI) creatinine equation is based on the same four variables as the modification of diet in renal disease (MDRD) Study equation, but uses a two-slope spline to model the relationship between estimated GFR and serum creatinine, and a different relationship for age, sex, and race. The equation was reported to perform better and with less bias than the MDRD Study equation, especially in patients with higher GFR. This results in reduced misclassification of CKD.

ο   GFR = 141 × min(Scr/κ,1)α × max(Scr/κ,1) − 1.209 × 0.993Age × 1.018 [if female] × 1.159 [if black]

ο   Where Scr is serum creatinine (mg/dL), κ is 0.7 for females and 0.9 for males, α is −0.329 for females and −0.411 for males, min indicates the minimum of Scr/κ or 1, and max indicates the maximum of Scr/κ or 1.

   Use

   To diagnose renal insufficiency; more specific and sensitive indicator of renal disease than of BUN. Use of simultaneous BUN and creatinine determinations provides more information in conditions.

   Adjusting dosage of renally excreted medications.

   Monitoring renal transplant recipients.

   Serum creatinine levels are a proxy for reduced skeletal muscle mass.

   eGFR: Serum creatinine measurement is used in estimating GFR for people with CKD and those with risk factors for CKD (DM, hypertension, cardiovascular disease, and family history of kidney disease).

   Interpretation