Table 1 shows the demographics of patients. They were also more likely to be female and had lower baseline creatinine values. Table 2 shows renal and hospital outcomes. Sixteen hundred patients recovered renal function during their hospital stay. Table 3 shows the results of the multivariable logistic regression analysis for hospital mortality. Patient characteristics and outcomes among patients with different BCRs are shown in Supplementary Table 1.
Since approximately three quarters of the patients did not have a known baseline creatinine and it was calculated with the MDRD equation, sensitivity analysis was conducted separately by studying only patients with more than one admission measured baseline creatinine available.
Demographics of patients, renal and hospital outcome and multivariable logistic regression analysis for hospital mortality are shown in Supplementary Tables 2 , 3 and 4. These results were almost identical to those for all patients. We found that this diagnostic test failed on several grounds. Firstly, we did not find a bimodal distribution of BCR. Additionally, we confirmed that, even after adjustment for several major confounding variables, the association between a high BCR and mortality remained greater than for a low BCR value.
Finally, when we analyzed the association between BCR and outcome, we found that it had a J-shaped curve with the lowest mortality in the 15—20 range. BCR has been used to distinguish PRA and ATN for decades, although more recently the usefulness of such terms has been called into question and may not be appropriate or correct [ 3 , 11 ].
However, actual clinical evidence to support the theory is scarce and dated [ 13 , 14 ]. More recently, Tariq et al. BUN has been known to be a risk factor for mortality in variety of conditions: e. BUN is also included in general severity scores for critically ill patients [ 27 ]. Recently, Beier et al.
Feinfeld et al. These observations strongly suggest that BUN is modulated by a number of mechanisms e. Apart from mortality, we found that there were several differences between high BCR and low BCR that suggests that patient characteristic and the nature and severity of disease are more important determinants of the BCR than renal factors.
This study contains several limitations. Firstly, this is a single-center study that limits its generalizability. However, it was conducted in a large academic center, which shares the typical characteristics of other similar centers in resource-rich countries.
As such, it should provide useful information to help clinicians understand the nature of BCR as a diagnostic and prognostic test. However, this threshold is typically used in reviews and textbooks [ 8 ]. Thirdly, creatinine may be a less sensitive marker of AKI in sicker individuals as acute and chronic illness can reduce muscle creatinine generation rate, slowing the rate of rise in creatinine after a fall in GFR.
Our study was the first to look at the clinical meaning of BCR. Our findings relationship between high BCR and mortality therefore need to be confirmed or refuted in other studies and in different health care systems. Future studies could focus on whether BCR, combined with other potential diagnostic tests used to separate PRA from ATN urinary sodium, fractional excretion of sodium or fractional excretion of urea , can still offer diagnostic value in patients with AKI.
However, we found that the BCR did not have a bimodal or near bimodal distribution and that the relationship between BCR and mortality was J-shaped. Additionally, and contrary to expectations, patients with suspected functional AKI had a higher hospital mortality compared with patients with a lower BCR, a finding confirmed with multivariable analysis. We would like to thank Mr Harvey Sutcliffe for his assistance in obtaining the central laboratory data and Mr Peter Davey for his assistance in obtaining the admissions and discharges information.
National Center for Biotechnology Information , U. We use procedural, physical, and electronic security methods designed to prevent unauthorized people from getting access to this information. Our internal code of conduct adds additional privacy protection. All data is backed up multiple times a day and encrypted using SSL certificates. See our Privacy Policy for more details. Optimal Result: 9 - 20 :1 ratio. Understand Lab Results. The level of creatinine in your blood also tells how well your kidneys are working—a high creatinine level may mean your kidneys are not working properly.
A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels. When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch. There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Rhoads MD - Internal Medicine. Author: Healthwise Staff. Medical Review: E. The ratio may be decreased with liver disease due to a decrease in the formation of urea and malnutrition. Urea is made in the liver as a by-product of protein metabolism. Thus, a high ratio is suggestive of prerenal disease as long as some other cause of a high ratio is not present. The BUN will rise out of proportion to the serum creatinine when urea production is increased due to GI bleed upper somewhat more than lower , tissue breakdown, or glucocorticoid therapy.
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