The Effect of Age, Sex, and Race on Urinary Markers of Kidney Damage in Children
Received 11 April 2007; accepted 23 August 2007. published online 31 October 2007.
Background
The aim of this study is to examine the effects of age, sex, and race on the excretion and concentrations of albumin, γ-glutamyl transpeptidase (γ-GT), N-acetyl-β-d-glucosaminidase (NAG), α1-microglobulin (α1M), and creatinine in children.
Study Design
Secondary analysis of a clinical trial, The New England Children’s Amalgam Trial, which examined effects of amalgam dental fillings.
Setting & Participants
534 children aged 6 to 10 years at baseline were recruited from Boston, MA, and rural Maine.
Predictors
Age, sex, and race.
Outcomes & Measurements
Urine samples were collected annually for 5 years and analyzed for creatinine, albumin, γ-GT, NAG, and α1M concentrations. Repeated-measures analysis of covariance was used to model effects of age, sex, and race on these values, as well as calculated excretion rates.
Results
All measures of creatinine and γ-GT increased significantly with age. Albumin and γ-GT concentration and excretion (milligrams per gram of creatinine or units per gram creatinine) were significantly greater for girls compared with boys. α1M concentration and creatinine excretion were greater for boys compared with girls. Creatinine concentration was significantly greater for blacks than for whites and Hispanics. Creatinine excretion and all γ-GT levels were significantly greater for blacks and Hispanics compared with non-Hispanic whites.
Limitations
The study population, recruited for a clinical trial, was of lower socioeconomic status than the general population. The high limit of detection for α1M resulted in a majority of samples less than the detection limit.
Conclusions
We recommend considering age, sex, and race in the interpretation of urinary markers. It also is recommended that epidemiological studies and clinical trials account for age, sex, and race in statistical models comparing urinary markers of kidney damage.
ABSTRACT