The applicability of urinary creatinine as a method of specimen normalization in the cystic fibrosis population.
BACKGROUND
Urine specimens are commonly used in biomarker research. Urinary creatinine (UCr) is often used to adjust for urine analyte concentration. We aim to explore the applicability of UCr as a normalization method in a cystic fibrosis (CF) population during hospitalization.


METHODS
Multiple spot urine samples were collected from CF patients hospitalized for a pulmonary exacerbation. Single spot specimens were obtained from asthmatics and healthy children for comparison. The assumptions and implications from the use of UCr as a normalization factor for urinary desmosine measurements were investigated.


RESULTS
UCr differed significantly across disease groups and decreased significantly over time in the CF population. Differing results were obtained when contrasting normalization by UCr with specific gravity.


CONCLUSIONS
UCr levels are not completely attributable to simply variations in urine concentration. Analysis of urinary biomarker measurements should be initiated with an understanding of the relative effects of the normalization process on the results.
Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Denver, 13001 E. 17th Place, B119, Aurora, CO, 80045, USA.
Brandie D
BD
Wagner
Frank J
FJ
Accurso
Theresa A
TA
Laguna
D000293:Adolescent; D001249:Asthma / Q000652:urine; D015415:Biomarkers / Q000652:urine; D016022:Case-Control Studies; D003404:Creatinine / Q000652:urine*; D003550:Cystic Fibrosis / Q000652:urine*; D018450:Disease Progression; D006801:Humans; D007297:Inpatients; D012016:Reference Values; D013046:Specific Gravity; D055815:Young Adult
D015415:Biomarkers; D003404:Creatinine