Urine Analysis

Over 19 million American adults have chronic kidney disease, and over 300,000 required dialysis or transplantation in 1999.

Moderate kidney disease is treatable, and urine tests play an important role in detecting and diagnosing this condition.

Urine creatinine, urea, and protein levels are all measured as a gauge of kidney function.

For example, the ratio of urea levels in urine and in serum can provide an indication of the efficiency of the kidney in filtering and removing urea from the bloodstream.

Summary of multianalyte IR-based method for the simultaneous determination of urea, protein, and creatinine as compared to reference analytical levels.

Since urea is a protein breakdown product, urine levels may also be measured to gauge the protein requirements of severely ill patients.

The creatinine clearance test gauges the glomerular filtration rate, i.e. the volume of filtrate made by the kidneys per minute.

The large protein molecules are normally filtered by the kidney, so that protein is normally not present in urine. Elevated urine protein levels may result if the kidney is diseased.

All three of these compounds may be assayed simultaneously from the mid-IR absorption spectra of dried urine films, providing analytical accuracy comparable to current methods but avoiding the costs associated with the purchase and storage of reagents which are typically required.

The mid-IR spectrum of an unusual urine specimen reveals:

Representative spectrum of a dried urine film.

• The overall appearance is dominated by urea absorptions, since urea is normally by far the most concentrated species.
• This sample is unusual in that it shows very strong protein absorptions, indicating the need for followup of this donor.
• An internal standard, potassium thiocyanate (SCN-), contributes an absorption at 2060 cm^-1. This absorption serves to normalize the spectra,
  compensating for random variations in film thickness.

References:

1. R.A, Shaw. S. Low Ying, M. Leroux, and H.H. Mantsch. "Toward reagent-free clinical analysis: Quantitation of urine urea, creatinine, and total protein from the mid-infrared spectra of dried urine films". Clinical Chemistry 46, 1493-5 (2000)
2. R.A. Shaw, S. Kotowich, H.H. Mantsch, and M. Leroux. "Quantitation of protein, creatinine, and urea in urine by near-infrared spectroscopy" Clinical Biochemistry 29, 11-19 (1996).

Related Information

Institutes:

• NRC Institute for Biodiagnostics