American Society of Radiologic Technologist (ASRT) Practice Exam

Which of the following statements is FALSE about the laboratory value GFR?

1. GFR stands for glomerular filtration rate

2. GFR is calculated from the results of a blood urea nitrogen (BUN) test

3. GFR estimates how much blood passes through the glomeruli of the kidney

4. GFR is a measure of kidney function and estimation of degree of kidney disease

The correct answer is: GFR is calculated from the results of a blood urea nitrogen (BUN) test

The statement that GFR is calculated from the results of a blood urea nitrogen (BUN) test is misleading when considering the specific function of GFR. While BUN is an important laboratory test used to assess kidney function, it is not the sole determinant used to calculate GFR. Instead, GFR is typically estimated using formulas that incorporate serum creatinine levels, age, gender, race, and body surface area. The most commonly used equation for estimating GFR is the MDRD (Modification of Diet in Renal Disease) equation or the Cockcroft-Gault formula, which emphasizes creatinine levels rather than BUN. The other statements accurately reflect the role and significance of GFR in evaluating kidney health. GFR indeed stands for glomerular filtration rate, which quantifies how much blood is filtered by the kidney's glomeruli. It is a critical measure of kidney function, providing insight into how well the kidneys are filtering waste and regulating fluid balance. Thus, the falsehood in the statement regarding GFR is rooted in its reliance on BUN for calculation, rather than the broader and more accurate uses of serum creatinine measurements in GFR assessments.