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A model to predict 24-h urinary creatinine using repeated measurements in an occupational cohort study.

Authors
Kroos-DS; Mays-JE; Harris-SA
Source
J Expo Sci Environ Epidemiol 2010 Sep; 20(6):516-525
NIOSHTIC No.
20038188
Abstract
Creatinine measurements can be used to standardize urinary pesticide concentrations and to estimate "completeness" of urine collections. Published statistical models exist to predict 24-h creatinine, but many were developed assuming independence among observations. Using correlated repeated measurement data collected from an occupational cohort, the objectives were to create a predictive model for 24-h urinary creatinine and to compare the predictive capability of this model to earlier published models. Using a mixed-model methodology, the appropriate covariance structure was identified and utilized to model the measurements. A backwards elimination model building technique applied to the model building data set (110 adult male subjects and 457 creatinine values) yielded a final model that included variables for body mass index (BMI), height, diabetes, allergies, medical conditions that affect kidney function, use of creatine supplements, and anti-inflammatory medications. Using an external model validation data set (21 adult male subjects' creatinine values, n=91 observations from a total of 275) the predictive performance of the model was evaluated using the mean square prediction error (MSPR) and the Pearson's correlation coefficient (r); its performance was better (MSPR=279184, r=0.43) than any of the earlier models investigated (MSPR: range 658860-393139; r, range 0.18-0.38). In conclusion, the use of a covariance structure that allowed repeated measurements for any one individual to be correlated, improved the predictive performance. For purposes of incomplete urine sample identification in observational studies, it is necessary to collect information in addition to age, gender, and BMI, which are typically used in these settings.
Keywords
Pesticides; Urinalysis; Urine-chemistry; Biomarkers; Statistical-analysis; Mathematical-models; Body-weight; Height-factors; Men; Kidney-function; Epidemiology; Medical-monitoring; Age-factors; Medical-screening; Medicinal-chemicals; Author Keywords: biological monitoring; covariance structure; creatinine; mixed model; occupational epidemiology; repeated measurements
Contact
Dr. Shelley A. Harris, Population Studies and Surveillance, University of Toronto, Cancer Care Ontario, 620 University Avenue, Toronto, ON, Canada M5G 2L7
CODEN
JEAEE9
Publication Date
20100901
Document Type
Journal Article
Email Address
Shelley.Harris@cancercare.on.ca
Funding Type
Grant
Fiscal Year
2010
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-004084
Issue of Publication
6
ISSN
1559-0631
Source Name
Journal of Exposure Science and Environmental Epidemiology
State
VA
Performing Organization
Virginia Commonwealth University, Richmond, Virginia
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