An unresolved issue: The relationship between spot urine protein

To investigate the relationship between spot urine protein-to-creatinine (sP/Cr) ratio and 24-h protein excretion in patients with different diagnoses. This retrospective study analysed data from the medical records of patients admitted for24-h proteinuria determination who also had sP/Cr ratio data for the same day. A total of 1222 urine samples obtained from 694 adult outpatients were analysed. The mean？±？SD age of the patients was 53.6？±？15.9 years. The mean？±？SD 24-h proteinuria and sP/Cr were 1.7？±？2.4 g/day and 1.8？±？2.4, respectively. The correlation between the sP/Cr and 24-h protein excretion was high (R2？=？0.89). The sP/Cr ratio accounted for 72% of the variability in 24-h proteinuria in the entire study population. Areas under the curve for 24-h proteinuria at 0.3 g/day, 1.0 g/day and 3.0 g/day were 0.940, 0.966, and 0.949, respectively. The mean？+？2SD limits of agreement were between +2.99 and –2.73 g/day according to the Bland Altman analysis. This current study found a clinically unacceptable deviation between 24-h proteinuria and sP/Cr ratio. Therefore, the sP/Cr ratio cannot replace 24-h proteinuria. A new method using spot urine protein and creatinine values that is able to minimize under or over estimation is still warranted