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Question 2#

B. 24-hour creatinine clearance overestimates true GFR by 5%, and thus, as GFR declines, tubular secretion increases in response to increasing creatinine levels may contribute upto 10%–15% of all creatinine levels at GFR levels of 40–80 mL/min. At best, then, the CrCL should be considered the ‘upper limit’ of the true GFR

C. Cockcroft-Gault measures creatinine clearance by the formula: CrCl = {[(140 – age) × (Lean Body Weight in kg)]/[Serum Creatinine (mg/ dL) × 72]} × 1.05 (women)

D. The simplest estimate of GFR is the four-variable equation (PCr, weight, sex and ethnicity), which estimates GFR using the formula: eGFR (mL/min/ 1.73 m) = 186 × (Serum Creatinine [mg/dL])−1.154 × (weight in kg)−0.203 × (0.742 if female) × (1.210 if African American)

E. MDRD, which is used to calculate the eGFR is not validated for use in children, whilst CG formula overestimates CrCl in children due to reabsorption

Correct Answer is A

Comment:

Question 2#

Which of the following is CORRECT regarding GFR?

A. The best estimate of GFR can be obtained by measuring the rate of clearance of a given substance from the plasma, and inulin clearance is felt to be the best measure of GFRB. 24-hour creatinine clearance overestimates true GFR by 5%, and thus, as GFR declines, tubular secretion increases in response to increasing creatinine levels may contribute upto 10%–15% of all creatinine levels at GFR levels of 40–80 mL/min. At best, then, the CrCL should be considered the ‘upper limit’ of the true GFR

C. Cockcroft-Gault measures creatinine clearance by the formula: CrCl = {[(140 – age) × (Lean Body Weight in kg)]/[Serum Creatinine (mg/ dL) × 72]} × 1.05 (women)

D. The simplest estimate of GFR is the four-variable equation (PCr, weight, sex and ethnicity), which estimates GFR using the formula: eGFR (mL/min/ 1.73 m) = 186 × (Serum Creatinine [mg/dL])−1.154 × (weight in kg)−0.203 × (0.742 if female) × (1.210 if African American)

E. MDRD, which is used to calculate the eGFR is not validated for use in children, whilst CG formula overestimates CrCl in children due to reabsorption

Correct Answer is A

Comment:

Answer A

The 24-hour creatinine clearance (CrCl) overestimates true GFR by 10%–20% and thus as GFR declines, tubular secretion increases in response to increasing creatinine levels may contribute upto 35% of all creatinine levels at GFR levels of 40–80 mL/min. At best, then, the CrCL should be considered the ‘upper limit’ of the true GFR. Cockcroft-Gault measures creatinine clearance by the formula − CrCl = {[(140-age) × (Lean Body Weight in kg)]/[Serum Creatinine (mg/dL) × 72]} × 0.85 (women). It underestimates CrCL in children due to reabsorption. Moreover, the calculation is dependent on accurate collection of the specimen, which can be incomplete. The MDRD formula to estimate GFR is eGFR (in mL/min/1.73 m) = 186 × (Serum Creatinine [mg/dL])^{−1.154} × (age)^{−0.203} × (0.742 if female) × (1.210 if African American). However, this formula is not validated for use in children, whilst Cockcroft-Gault formula overestimates CrCl in children due to reabsorption.