Confirming the Utility of Four Kidney Biomarker Tests in a Longitudinal Follow-Up Study

Abstract

In this follow-up study, 526 persons were followed for almost 5 years to assess the reversibility and predictive value of four kidney biomarkers in a field epidemiology setting. This study examined (a) whether elevations in urinary albumin, N-acetyl-β-d-glucosaminidase, retinol-binding protein, and alanine aminopeptidase remained elevated at follow-up and (b) whether these initial elevations were predictive of kidney disease (as measured by markers of kidney dysfunction: serum creatinine, serum cystatin C, creatinine clearance, and urine osmolality) at follow-up. Study participants were 8–76 years of age at baseline and were followed for an average of 4.5 years. Approximately 50% of adults who had an elevated biomarker did not have an elevation at followup. Youths with elevated biomarkers at baseline, but who completed adolescence by the time of the follow-up, no longer had any elevations in biomarkers at follow-up. Adult participants who had elevated biomarkers and selected health conditions at baseline (diabetes and, to a lesser extent, heart disease, hypertension, gout, and urinary tract disease) were more likely to show early indicators of kidney impairment at follow-up. Participants with these health conditions and normal kidney biomarker values at baseline had kidney test results at follow-up that were similar to results of study participants who did not have these health conditions at baseline. The presence or absence of elevated biomarkers at baseline among generally healthy participants was not associated with the development of early indicators of kidney impairment at follow-up. This longitudinal study confirmed the utility of these four kidney biomarker tests as markers of preclinical organ dysfunction among adults with certain preexisting medical conditions.

• Alanine aminopeptidase
• Biomarkers
• Albumin
• N-acetyl-β-d-glucosaminidase
• Retinol-binding protein
• Creatinine clearance
• Cystatin C
• Creatinine
• Kidney disease

Abbreviations
AAP:	=	Alanine aminopeptidase
ALB:	=	Albumin
ATSDR:	=	Agency for Toxic Substances and Disease Registry
BUN:	=	Blood urea nitrogen
LMW:	=	Low molecular weight
NAG:	=	N-Acetyl-β-d-glucosaminidase
NC:	=	Cannot be computed
RBP:	=	Retinol-binding protein