What is the Difference Between sCr, eGFR, ACR, and BUN
Raymond, Janice L., et al. Krause and Mahan’s Food and the Nutrition Care Process. Elsevier, 2021.
Are there any tips to address a high BUN/creatinine ratio?
Evaluation of any biomarker or biomarker ratio requires a bit of investigation to find out which biomarker is trending high or low, and why.
In this case, the reason for the increased BUN:Creatinine Ratio is that the BUN is above optimal and creatinine is below optimal. With an elevated BUN, you need to investigate the possibility of dehydration, a high protein diet, etc.
The creatinine trending low and being below optimal could be due to reduced muscle mass, sarcopenia, and debilitation.
Kidney dysfunction is less likely because the creatinine is trending low. It would be important to evaluate the eGFR to confirm that renal clearance/function is good.
Review of medical history is imperative to assess renal function over time, cardiovascular status, causes of muscle loss, etc.
- Further investigation is warranted, see the following entries regarding the current labs.
- If possible, review past labs in a series to identify ongoing trends.
High BUN:Creatinine Ratio
High BUN:Creatinine ratio may indicate transient kidney dysfunction, especially above 20 (Raymond 2021). Temporary non-renal causes of an increased ratio include excess protein intake, GI bleeding, catabolic states such as fever or burns), dehydration, shock, congestive heart failure, or urinary tract obstruction (Hosten 1990).
An elevated ratio is also associated with increased risk of coronary artery disease in type 2 diabetics (Liu 2022), mortality from myocardial infarction and acute heart failure (Qian 2019), poorer outcomes in those with congestive heart failure (Tolomeo 2023).and increased severity and mortality from COVID-19 (Ok 2021).
A BUN:Creatinine ratio above 15 was also associated with acute ischemic stroke due to venous thromboembolism caused by dehydration (Kim 2017), as well as poor outcomes in acute ischemic stroke (Schrock 2012).
High BUN
High levels of BUN are associated with renal dysfunction, dehydration, excess protein intake, GI bleeding, shock, burns, heart failure, and myocardial infarction, as well as with certain medications, including allopurinol, diuretics, antibiotics, and aspirin (Pagana 2021). Elevated BUN is observed in acute pancreatitis and may predict severity as well as mortality from the condition (Dai 2022, Lin 2017, Wu 2011). Other catabolic processes, such as fever and infection, can increase BUN as well (Hosten 1990).
Low creatinine
Low creatinine levels are associated with debilitation, decreased muscle mass, muscular dystrophy, and myasthenia gravis (Pagana 2021). A low serum creatinine associated with reduced muscle mass may increase the risk of type 2 diabetes (Harita 2009, Hu 2019).
Please review the following research articles:
- Sarcopenia
- Biomarkers of Kidney Function: BUN to Creatinine Ratio
- Biomarkers of Kidney Function: Blood Urea Nitrogen (BUN)
- Biomarkers of Kidney Function: Creatinine
References
Hosten, Adrian O. “BUN and Creatinine.” Clinical Methods: The History, Physical, and Laboratory Examinations, edited by H Kenneth Walker et. al., 3rd ed., Butterworths, 1990.
Kim, Hoon et al. “Elevated Blood Urea Nitrogen/Creatinine Ratio Is Associated with Venous Thromboembolism in Patients with Acute Ischemic Stroke.” Journal of Korean Neurosurgical Society vol. 60,6 (2017): 620-626. doi:10.3340/jkns.2016.1010.009
Liu, Feng et al. “Elevated blood urea nitrogen-to-creatinine ratio increased the risk of Coronary Artery Disease in patients living with type 2 diabetes mellitus.” BMC endocrine disorders vol. 22,1 50. 28 Feb. 2022, doi:10.1186/s12902-022-00954-3
Ok, Fesih et al. “Predictive values of blood urea nitrogen/creatinine ratio and other routine blood parameters on disease severity and survival of COVID-19 patients.” Journal of medical virology vol. 93,2 (2021): 786-793. doi:10.1002/jmv.26300
Pagana, Kathleen Deska, et al. Mosby’s Diagnostic and Laboratory Test Reference. 15th ed., Mosby, 2021.
Qian, Hao et al. “Predictive value of blood urea nitrogen/creatinine ratio in the long-term prognosis of patients with acute myocardial infarction complicated with acute heart failure.” Medicine vol. 98,11 (2019): e14845. doi:10.1097/MD.0000000000014845
Raymond, Janice L., et al. Krause and Mahan’s Food and the Nutrition Care Process. Elsevier, 2021.
Salvador, López Giacoman et al. “A low BUN/creatinine ratio predicts histologically confirmed acute interstitial nephritis.” BMC nephrology vol. 24,1 75. 27 Mar. 2023, doi:10.1186/s12882-023-03118-0
Shen, Song et al. “The blood urea nitrogen/creatinine (BUN/cre) ratio was U-shaped associated with all-cause mortality in general population.” Renal failure vol. 44,1 (2022): 184-190. doi:10.1080/0886022X.2022.2030359
Schrock, Jon W et al. “Elevated blood urea nitrogen/creatinine ratio is associated with poor outcome in patients with ischemic stroke.” Clinical neurology and neurosurgery vol. 114,7 (2012): 881-4. doi:10.1016/j.clineuro.2012.01.031
Tolomeo, Paolo et al. “Independent prognostic importance of blood urea nitrogen to creatinine ratio in heart failure.” European journal of heart failure, 10.1002/ejhf.3114. 20 Dec. 2023, doi:10.1002/ejhf.3114
Zia Ziabari, Seyyed Mahdi et al. “Blood Urea Nitrogen to Creatinine ratio in Differentiation of Upper and Lower Gastrointestinal Bleedings; a Diagnostic Accuracy Study.” Archives of academic emergency medicine vol. 7,1 e30. 2 Jun. 2019
What is the Difference Between sCr, eGFR, ACR, and BUN?
There are different tests that healthcare professionals use to measure kidney function. Overall, these blood and urine tests are used to find out how well your kidneys are working, check for signs of kidney disease, and look for any changes in a person’s kidney health over time. The earlier kidney disease is found, the better the chance of slowing or stopping it from getting worse.
Serum Creatinine (sCr)
A serum creatinine test measures the amount of creatinine in your blood. Creatinine is a waste product that is produced from the normal wear and tear on muscles in your body. Waste products like creatinine are filtered out of the blood by healthy kidneys and leave your body in your urine. If your kidneys are not working as well as they should, then the amount of creatinine in your blood can increase. Therefore, measuring the amount of creatinine in your blood (serum creatinine, or sCr) is used to check kidney function (a creatinine urine test can also be used to measure creatinine in your urine). A sCr level of greater than 1.2 for women and greater than 1.4 for men may be an early sign that the kidneys are not working well. However, the “normal” creatinine level can depend on your age, race, gender, and body size. What is considered high for one person might be normal for another.
Estimated Glomerular Filtration Rate (eGFR)
Estimated glomerular filtration rate (eGFR) is calculated using serum creatinine and other factors, such as age and gender. This measurement accounts for the possible differences in creatinine levels between people, in order to find out the correct level of kidney function. In other words, eGFR measurements can help account for certain differences between people that measuring sCr alone does not. However, normal eGFR can still vary, mainly according to age (it can decrease as you get older). The normal value for eGFR is 90 or above. An eGFR below 60 is a sign that the kidneys are not working well. Once the eGFR decreases below 15, one is at high risk for needing treatment for kidney failure, such as dialysis or a kidney transplant.
Albumin-to-Creatinine Ratio (ACR)
Albumin-to-creatinine ratio (ACR) is a urine test to see how well your kidneys are working. First, the amount of albumin in your urine is measured. Albumin is the most common type of protein found in your urine. Higher amounts of albumin in the urine can be a sign that your kidneys are not working as well as they should. ACR is calculated by dividing the amount of urine albumin by the amount of urine creatinine. Albuminuria means that there is more albumin in the urine than there should be, which means the kidneys can be damaged. An ACR below 30 is considered normal. An ACR between 30-300 means you have moderately increased albuminuria. An ACR above 300 means you have severely increased albuminuria.
Blood Urea Nitrogen (BUN)
Blood urea nitrogen (BUN) is a blood test that is also used to test how well your kidneys are working. Urea nitrogen comes from the breakdown of protein in the foods you eat. Normally, nitrogen in the blood binds to other wastes that are filtered by the kidneys and leave your body in your urine. The BUN test measures the amount of urea nitrogen in your blood. If your kidneys are not working as well as they should, then the amount of urea nitrogen can be higher. A normal BUN level is between 7 and 20. As kidney function decreases, the BUN level can rise. However, there are other causes of a high BUN that may not mean that there is a problem with your kidneys. For example, certain medications such as prednisone, or tetracycline antibiotics can cause such increases. Bleeding in the stomach and intestines can also cause BUN to rise. It is therefore important for your healthcare professional to discuss these factors with you.
