Bioanalytical comparison between dried urine spots and liquid urine bioassays used for the quantitative analysis of urinary creatinine concentrations

Background: quantitative bioassays for determination of urinary creatinine concentrations using liquid urine and dried urine on paper disks (DUPD) specimens were developed and validated. The bioassays were cross-validated by means of measurement of the urinary creatinine concentrations applying DUPD (3 and 5 mm) and liquid urine specimens. Results: LLOQ and LOD for all bioassays were 0.88 and 0.27 mmol/l creatinine, respectively. All bioassays were cross-validated by the analysis of urine samples from healthy voluntary individuals and bioassays performed were statistically not significantly different. Mean observed urinary creatinine concentrations ranged between 0.44 and 25.6, 0.24 and 23.9, 0.13 and 31.26 mmol/l...