Cystatin CCystatinsCreatinineNephelometry and TurbidimetryGlomerular Filtration RateBiological MarkersAscorbic AcidCystatin ACystatin BAscorbic Acid DeficiencyHemoglobin A, GlycosylatedSalivary CystatinsProtein CGastric JuiceCysteine Proteinase InhibitorsKidney Function TestsCerebrospinal Fluid ProteinsPredictive Value of TestsCathepsin BPapainAntioxidantsCathepsinsCytochrome c GroupLipocalinsProspective StudiesVitamin EBlood GlucoseRisk FactorsKidney DiseasesCathepsin HCohort Studies