QuantiChrom Urea Assay Kit from BioAssay Systems

As a laboratory that works in the field of kidney disease research, we are interested in the ability to measure kidney function. One of the most common parameters measured in a clinical setting is blood urea nitrogen (BUN), which measures the amount of nitrogen in the blood in the form of urea. When kidney function is compromised, the normal level (~20mg/dL) of BUN increases. Although BUN can be accurately determined in a clinical environment using a machine such as an AutoAnalyzer, we desired a method that would enable us to determine BUN levels in-house using our own samples.

The QuantiChrom Urea Assay Kit from BioAssay Systems is provided as an easy-to-use, two reagent format. Working reagent is prepared immediately prior to use by mixing together equal volumes of reagent A and B. This working reagent is then added to your samples of interest and the colorimetric reaction is allowed to proceed at room temperature for 20min. The intensity of the color formed, which is determined by the OD520nm value, is directly proportional to the concentration of urea in the sample.

Although the kit suggests only running one urea standard per assay (a 1ml stock of 50mg/dL urea is provided), we routinely run a dilution series of standards (10mg/dL up to 100mg/dL in 10mg/dL increments) and plot them on a line. In our opinion, this results in a much better controlled assay and more accurate determination of urea values in unknown samples, which we read directly from the line. Since we deal with models that exhibit chronic renal failure we often prepare a few additional dilutions of our samples to ensure one of the values falls on the line of the standards plot.

The kit comes with all the reagents necessary to perform about 500 assays in 96-well plate format. Since blood urea is often represented as BUN values, a helpful conversion factor allowing easy conversion between the two is provided in the instructions.

We have been very happy with this kit, which we use on a routine basis to measure urea concentration in plasma and serum samples. It is easy to use, requires minimum hands-on time and the results obtained are reliable and reproducible.