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Screening with blood urea nitrogen before intravenous contrast
1Division of Emergency Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA. mwitt001@umaryland.edu
The American Journal of Emergency Medicine
|October 24, 2003
Summary
Blood urea nitrogen (BUN) can effectively screen for renal insufficiency before creatinine results are available. A BUN level below 15-20 mg/dL strongly suggests normal kidney function, aiding in contrast media decisions.
Area of Science:
- Nephrology
- Clinical Chemistry
- Radiology
Background:
- Blood urea nitrogen (BUN) and creatinine are key indicators of kidney function.
- BUN values are often available sooner than creatinine levels in clinical settings.
- Accurate and timely assessment of renal function is crucial for safe intravenous contrast administration.
Purpose of the Study:
- To evaluate the utility of blood urea nitrogen (BUN) as a screening tool for renal insufficiency.
- To establish reliable BUN cutpoints for predicting elevated creatinine levels (>Â/=2.0 mg/dL).
- To determine if BUN can be used to safely screen patients prior to intravenous contrast administration.
Main Methods:
- Retrospective analysis of laboratory records from 5000 consecutive patients to derive BUN cutpoints.
- Validation of derived cutpoints using a separate random sample of 2000 patients.
- Calculation of sensitivity, specificity, and negative likelihood ratios for identified BUN cutpoints.
Main Results:
- A "sensitive" BUN cutpoint of >Â/=15 mg/dL demonstrated a sensitivity of 0.997 and specificity of 0.56.
- A "high-yield" BUN cutpoint of >Â/=20 mg/dL showed a sensitivity of 0.98 and specificity of 0.71.
- Negative likelihood ratios were low (0.005 and 0.03), indicating strong evidence against renal insufficiency when BUN is below these thresholds.
Conclusions:
- Blood urea nitrogen (BUN) values can serve as an effective and rapid screening tool for renal insufficiency.
- BUN levels <15-20 mg/dL provide significant reassurance of adequate kidney function for contrast administration.
- Utilizing BUN for screening can expedite decisions regarding intravenous contrast use, improving workflow efficiency.