Reference intervals for the markers of proteinuria with a standardised bed-rest collection of urine

Reference intervals for markers of proteinuria or glomerular charge selecti vity were measured in 61 healthy female and 61 healthy male individuals. Ti med bed-rest and daytime collections were used to assess significance of pr eanalytical variability of results. Bedrest collections are advisable for r esearch on renal damage, whereas in routine care, robust protein/creatinine ratios work as practical estimates of protein excretion rates, the correla tions to excretion rates improving with increasing proteinuria. For glomeru lar charge selectivity, pancreatic/salivary isoamylase clearance ratio show ed lower within-subject biological variation than IgG/IgG4 clearance ratio, allowing more accurate classification into normal and reduced charge selec tivity. With our method, the lower 2.5% reference intervals for isoamylase clearance ratio were 1.1 in men and 1.9 in women.